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Background Digital flexor tendon sheath (DFTS) pathology is an important cause of lameness in horses. The outcome after surgical treatment is variable and depends on the exact diagnosis. Objectives To (1) describe the prevalence of lesions associated with lameness caused by nonseptic DFTS tenosynovitis in a large population of German sports and pleasure horses; (2) determine the sensitivity and specificity of diagnostic imaging techniques for identifying lesions within the DFTS with tenoscopic diagnosis being the gold standard; (3) explore associations between tenoscopically diagnosed lesions and signalment, purpose, and limb affected; and (4) describe the outcome following DFTS tenoscopy with nonseptic DFTS tenosynovitis in this population. Study design Retrospective case series. Methods Medical records of horses admitted for tenoscopic surgery of nonseptic DFTS tenosynovitis between 2011 and 2020 were reviewed. Follow‐up information was obtained via telephone contact. Sensitivity and specificity of ultrasonography and contrast tenography were determined using tenoscopic diagnosis as gold standard and univariable analysis was used to explore associations between signalment, case history, and tenoscopic diagnosis. Results Medical records from 131 horses were retrieved, of which 8 horses had bilateral disease and 6 horses were presented for tenoscopy on two separate occasions (3 for tenoscopy in the same limb, 3 in a different limb), thus, making a total of 145 limbs. Lesions were most commonly diagnosed in the deep (DDFT; n = 55 limbs) and superficial (SDFT; n = 55 limbs) digital flexor tendons. Manica flexoria (MF) lesions were detected in 44 limbs and palmar/plantar annular ligament (PAL) constriction in 99 limbs. In 36 limbs, only one structure within the DFTS was injured, whereas in 109 limbs a combination of lesions was noted, the most common being the combination of a SDFT lesion with PAL constriction. All affected limbs were examined with diagnostic ultrasonography; contrast tenography was performed in 86 limbs. For diagnosis of MF and DDFT tears, tenography was more sensitive (89% [confidence interval, CI: 65.4%–95.2%]; 72% [CI: 46.4%–89.3%], respectively) than specific (64% [CI: 52.5%–77.6%]; 53% [CI: 42.2%–73.3%], respectively) whereas ultrasonography was more specific (92% [CI: 84.5%–96.3%]; 92% [CI: 83.6%–96.0%]) with lower sensitivity (64% [CI: 47.7%–77.2%]; 54% [CI: 39.5%–67.9%]). For SDFT lesions, ultrasonography was highly specific (94% [CI: 86.9%–97.9%]) with lower sensitivity (66% [CI: 51.3%–77.4%]). Follow‐up information following first surgery was obtained for 118 horses (132 limbs): 18 (15.3%) of 118 horses remained chronically lame, 40 (33.8%) performed at a reduced level and 60 (50.8%) performed at the same or higher level following rehabilitation after tenoscopy. Horses with DDFT lesions had the poorest outcomes with only 36.6% returning to the same or higher level of exercise. Main limitations Retrospective analysis of clinical records and subjective outcome assessment based on owner follow‐up with potential recall bias. Findings on diagnostic imaging are impacted by many factors including equipment quality and operator expertise and experience. Conclusion Diagnostic imaging techniques were complimentary and contrast tenography was sensitive and ultrasonography was specific for the diagnosis of MF and DDFT lesions. Following tenoscopic surgery for nonseptic tenosynovitis of the DFTS, approximately half the cases were able to return to preinjury level of exercise.

BACKGROUND The evaluation of hindlimb lameness remains a major challenge in everyday clinical practice. In the absence of clear guidelines, veterinarians use different visual assessment methods for this task whose robustness is unknown. OBJECTIVES Determination of the robustness of five visual hindlimb lameness assessment methods based on the comparison of left and right tuber coxae movement. STUDY DESIGN Validated mathematical hindlimb lameness model based on experimental data from the literature. METHODS Vertical movement of left (LTC) and right (RTC) tuber coxae was simulated for the range of common hindlimb lameness movement patterns which horses present with in practice. Lameness severity ranged from sound to moderately lame (0% to 60% movement asymmetry). The scenarios of a pelvis held tilted and asymmetrical pelvic roll were included to reflect possible adaptations in pelvic rotation. Across all conditions, the outcomes for five different visual assessment methods based on comparative tubera coxarum movement were quantified, including hip hike, -drop and range of motion. The robustness of each assessment method was established through comparison to sacrum-based overall movement asymmetry as the ground truth. RESULTS Tubera coxarum based lameness assessment was highly sensitive to all the unique lameness patterns and changes in pelvic rotation which a lame horse may adopt. None of the five visual lameness assessment methods was 100% robust across all conditions tested. For everyday clinical practice, comparing the upward movement amplitude of the RTC before right hind foot contact and of the LTC before left hind foot contact (Hip_hike_diff) would be the most robust single tubera coxarum based visual assessment method. MAIN LIMITATIONS In the absence of published data regarding the frequency of different movement patterns and hip rotation adaptations in clinical practice, this study cannot indicate the proportion of assessments that would be incorrect for a given visual assessment method. CONCLUSIONS Using a single tubera coxarum based visual hindlimb lameness assessment method may lead to incorrect clinical judgement. Therefore, using multiple assessment methods would be beneficial to substantiate impressions.

Background Bone stress injuries and fatigue fractures of the pelvis are reported in only a small number of endurance horses. Objectives To describe bone stress injuries and fatigue fracture of the pelvis in endurance horses trained and competing on the deep sand surfaces. Study design Retrospective case series. Methods Medical records of horses used for endurance and diagnosed with bone stress injuries and/or fatigue fractures of the pelvis by ultrasound were reviewed. The bone stress injuries and fatigue fractures were classified as affecting the iliac wing, the iliac shaft, the tuber ischiadicum, the rest of the ischium or the pubis and subdivided into four fracture configurations: isolated iliac fracture, isolated fracture of the floor of the pelvis, isolated tuber ischiadicum fracture and multiple fractures. Descriptive statistics were performed overall and on fracture configurations for age, sex, breed, level of activity, affected limbs, previous injuries, development of the injury, seasons in the UAE, physical and dynamic findings and outcome. For each fracture configuration and the outcome, multivariable logistic regression models were developed after univariable logistic regression and collinearity analyses. Significance was set at P ≤ .05. Results Sixty endurance horses were included; 48% (95% CI: 36%-61%) had isolated iliac fracture, 17% (7%-26%) isolated fracture of the floor of the pelvis, 15% (6%-24%) isolated tuber ischiadicum fracture and 20% (10%-30%) had multiple fractures. Breed (OR, 4.42; 95%CI, 1.02-19.57) was significantly associated with isolated iliac fracture and asymmetry of bone landmarks (OR, 7.42; 95% CI, 1.47-37.45) with isolated tuber ischiadicum fracture. Degree of lameness (OR, 3.08; 95% CI, 1.07-8.9) and trotting on three tracks (OR, 8.62; 95% CI, 1.43-51.9) were significantly associated with the diagnosis of isolated fracture of the floor of the pelvis. Main limitations Data acquired in a single country. Conclusions Bone stress injuries and fatigue fractures of the pelvis can affect endurance horses trained and competing on deep sand. Isolated bone stress injuries and/or fatigue fractures of the ileum were the commonest followed by multiple pelvic bones involvement. The presence of lameness and trotting on three tracks suggest the presence of bone stress injuries and/or fatigue fractures of the floor of the pelvis; asymmetry of bony landmarks is more commonly detected in horses with bone stress injuries and/or fatigue fractures of the tuber ischiadicum.

Background Correct diagnosis and characterisation of deep digital flexor tendon (DDFT) lesions in equine athletes allows targeted treatment and improved prognostication. Objectives To assess the prevalence and character of pathological change within the DDFT in the pastern with concurrent tendon injury distally. It is hypothesised that tendon lesions in the pastern will be associated with tendinopathy within the hoof capsule. Study design Retrospective descriptive case series. Methods Cases with DDFT lesions in the pastern and magnetic resonance imaging (MRI) or ultrasonography of the foot were evaluated retrospectively. Lesion location and type were recorded. Odds ratios were calculated to determine the associations between more distal tendinopathy and the presence of different DDFT lesion types in the pastern. Results Thirty-four MRI scans of 33 horses and 64 ultrasonographic exams of 58 horses were analysed. Lesion location and type were recorded. Distal DDFT lesions were found in 75% (95% CI: 66.0-84.0) of total cases of pastern DDF tendinopathy and in 97% (95% CI: 91.6-100.0) of cases with core lesions of the DDFT in the pastern. A core lesion in the pastern was significantly more likely (OR = 20.7, 95% CI: 2.2-191.0; P = .008) to be associated with injury in the foot than other types of pastern lesion. Main limitations MRIs of the foot were not obtained on all included limbs which did not allow for fully inclusive evaluation of DDFT lesions distal to the navicular bone. Conclusions DDFT pathological change in the pastern, particularly core lesions, is associated with additional tendinopathy within the hoof capsule. When a DDFT lesion is found in the pastern, further imaging of the tendon within the foot is indicated to direct appropriate treatment and improve prognostication.

BACKGROUND The increasing popularity of objective gait analysis makes application in prepurchase examinations (PPE) a logical next step. Therefore, there is a need to have more understanding of asymmetry during a PPE in horses described on clinical evaluation as subtly lame. OBJECTIVES The objective of this study is to objectively compare asymmetry in horses raising minor vet concerns in a PPE and in horses raising major vet concerns with that found in horses presented with subtle single-limb lameness, and to investigate the effect of age/discipline on the clinicians' interpretation of asymmetry on the classification of minor vet concerns in a PPE. STUDY DESIGN Clinical case-series. METHODS Horses presented for PPE (n = 98) or subjectively evaluated as single limb low-grade (1-2/5) lame (n = 24, 13 forelimb lame, 11 hindlimb lame), from the patient population of a single clinic, were enrolled in the study provided that owners were willing to participate. Horses undergoing PPE were assigned a classification of having minor vet concerns (n = 84) or major vet concerns (n = 14) based on findings during the dynamic-orthopaedic part of the PPE. Lame horses were only included if pain-related lameness was confirmed by an objective improvement after diagnostic analgesia exceeding daily variation determined for equine symmetry parameters using optical motion capture. Clinical evaluation was performed by six different clinicians, each with ≥8 years of equine orthopaedic experience. Vertical movement symmetry was measured using optical motion capture, simultaneously with the orthopaedic examination. Data were analysed using previously described parameters and mixed model analysis and least squares means were used to calculate differences between groups. RESULTS There was no effect of age or discipline on the levels of asymmetry within PPE horses raising minor vet concerns. MinDiff and RUD of the head discriminated between forelimb lame and PPE horses raising minor vet concerns; MinDiff, MaxDiff, RUD of the Pelvis, HHDswing and HHDstance did so for hindlimb lameness. Two lameness patterns differentiated both forelimb and hindlimb lame from PPE horses with minor vet concerns: RUD Poll + MinDiff Withers - RUD Pelvis and RUD Pelvis + RUD Poll - MinDiff Withers. Correcting for vertical range of motion enabled differentiation of PPE horses with minor vet concerns from PPE horses with major vet concerns. MAIN LIMITATIONS Objective data only based on trot on soft surface, limited number of PPE horses with major vet concerns. CONCLUSIONS Combinations of kinematic parameters discriminate between PPE horses with minor vet concerns and subtly lame horses, though overlap exists.

Background Injuries to the oblique (ODSL) or straight (SDSL) distal sesamoidean ligaments are a recognised cause of distal limb lameness in the horse. However, there are only limited publications addressing common diagnostic features and prognosis. Objectives (a) Report findings on ultrasonography and standing low-field magnetic resonance imaging (sMRI) in horses with ODSL or SDSL injury; (b) Identify clinical variables associated with lesion type and (c) Identify factors associated with return to soundness in horses with ODSL or SDSL injury. Study design Retrospective case series. Methods Horses with a primary diagnosis of ODSL or SDSL injury confirmed with a combination of diagnostic analgesia and detection of a lesion on imaging (ultrasonographic ± advanced imaging) were included. Return to soundness and performance follow-up data were obtained. Results Fifty-one horses were included. SDSL injuries were more common in the forelimb (13/21, 62%), while ODSL injuries had equal frequency in fore- (15/30, 50%) and hindlimbs (15/30, 50%). ODSL injuries were more likely than SDSL injuries to affect the proximal third of the ligament (OR =13; 95% CI 2.3-74.3; p = 0.004) and often presented with periligamentar swelling (20/30;67%) and focal pain (22/28;79%). Lesions were frequently detected using ultrasonography (35/42;83%) and sMRI examination (18/25;72%). Only 27/49 cases (55%) returned to soundness, with only 15/49 (31%) returning to intended use. There were no significant associations between outcome and clinical features or treatment. Main limitations There was no comparative "gold standard" to validate lesions such as high-field MRI or histopathology. Conclusions In contrast to previous studies, ODSL and SDSL injuries were readily identified ultrasonographically using appropriate views, and with sMRI. Given the limited availability, cost and general anaesthetic risks associated with high-field MRI, more focus should be placed on optimising the ultrasonographic examination. Owners of affected horses should be informed of the guarded prognosis for return to full use.

Background In the last 30 years, several treatments have been proposed to treat subchondral cystic lesions (SCLs) but there have been no randomised studies to compare different methods and there is no consensus as to the optimal treatment. Objectives To evaluate a biocompatible absorbable implant for the treatment of SCLs in young horses in different anatomical locations. Study design Retrospective case series. Methods Horses with SCLs were treated with debridement through a trans-cortical extra-articular approach and an absorbable implant was inserted in the cavity. Clinical and radiographic follow-up was recorded and follow up ranged from 28 to 46 months (mean 37 months). Racing records were reviewed. Results Thirty-eight horses between 10 and 24 months of age were included in the study. In 36 of 38 horses treated, lameness resolved, and 77% average filling of the cyst was measured 120 days after surgery on radiographs. In two cases, surgical complications were recorded. Main limitations Information about the resorption of the implant is not available. Radiographs were performed in various hospitals or at farms or training stables, therefore, possible minor variations in technique and positioning occurred. Conclusions The extra-articular approach to the SCLs followed by the insertion of the absorbable implant led to clinical and radiographic improvement of the SCLs at 120 days after surgery. This technique, feasible in different anatomical locations, may offer an alternative to treat SCLs in young horses.

Background Compensatory lameness is common in horses and evaluation can be challenging. Objectives To investigate patterns of compensatory movements in clinical cases with fore- or hindlimb lameness before and after diagnostic analgesia. Study design Retrospective clinical study. Methods Multiple limb lameness of 367 horses was characterised by type (push-off, impact or mixed), limb (fore- or hindlimb in predominant lameness) and side (ipsi- or contralateral in concurrent lameness) using a body-mounted inertial sensor (BMIS). Diagnostic analgesia was performed until the percentage improvement of the vector sum in forelimb lameness and the mean difference of the maximum or minimum pelvic height (PDmax or PDmin) in hindlimb lameness was >= 50%. Linear mixed model and post-estimation of effects were performed by contrast command with multiple comparisons adjusted by Bonferroni method. Correlation of pre- and post-analgesia of all head and pelvis asymmetry parameters was tested with Spearman's rank correlation. Results Improvement in vector sum per mm after diagnostic analgesia in forelimb impact lameness positively correlated with decrease in PDmax in contralateral mixed lameness (0.187 mm, r = .58, P < .05). Improvement in PDmin per mm after diagnostic analgesia in hindlimb mixed and PDmax in hindlimb push-off lameness decreased vector sum in ipsilateral forelimb impact lameness by 0.570 and 0.696 mm, respectively (P < .05), with no positive correlation. Main limitations A variety of cases with inhomogeneous distribution of lameness patterns was investigated retrospectively, therefore, it is impossible to distinguish between true multiple limb lameness and compensatory lameness in this clinical material. Conclusions Various asymmetry patterns of concurrent lameness were seen in horses with naturally occurring primary forelimb impact lameness with contralateral compensatory hindlimb lameness with a mixed component being the most common. In horses with hindlimb lameness, compensatory movements were seen in ipsilateral forelimbs, mostly as an ipsilateral impact lameness during straight line trot.

Background: There is a paucity of research describing the gait pattern of lame horses at the walk. Objectives: To describe the changes in motion pattern and vertical ground reaction forces (GRFz) in horses with induced forelimb lameness at the walk and compare those changes with the changes observed at the trot. Study design: Experimental study. Methods: In 10 clinically sound Warmblood horses, moderate forelimb lameness was induced using a sole pressure model followed by trot and walk on a treadmill. Kinematic data were collected using 3D optical motion capture (OMC), and GRFz by an instrumented treadmill. Mixed models were used to compare sound baseline versus forelimb lameness (significance was set at P

Background Increased 18 F-Sodium Fluoride (18 F-NaF) uptake at the chondrosesamoidean ligament (ChSL) attachment on the distal phalanx was identified in an exploratory positron emission tomography (PET) study. The prevalence and significance of this lesion has not been previously investigated. Objectives The goal of this study was to assess the prevalence of this lesion, its association with other imaging findings and with clinical signs. Study design Retrospective cross-sectional analytical study. Methods All horses with 18 F-NaF PET and computed tomography (CT) imaging of the feet performed between October 2016 and December 2017 were included in the study. All PET scans were independently assessed by two radiologists for increased uptake at the ChSL attachment site and concurrent imaging was reviewed. Clinical findings, treatment and outcome were retrieved from the medical records. Results Fourteen of 30 horses (20/56 feet) had increased 18 F-NaF uptake in the region of interest. ChSL enthesopathy was the primary lesion in three horses. Other PET abnormalities included navicular bone uptake (13 feet) and ipsilateral palmar process uptake (9 feet). There was no significant association between ChSL enthesopathy and other lesions. ChSL enthesopathy was significantly associated with foot lameness. CT abnormalities at the ChSL attachment were initially identified in one foot, and retrospectively noted in another five following the results of PET imaging. Main limitations The study is retrospective and there was a limited sample size. Conclusions PET led to identification of ChSL enthesopathy in a large proportion of horses with foot pain. This finding is most commonly associated with other lesions but may also represent the main abnormality. The axial border of the palmar processes of the distal phalanx should be carefully assessed on cross sectional imaging to identify this lesion. ChSL enthesopathy may be an important but previously not recognised component of foot pathology in horses.

BACKGROUND Pathology involving the oblique sesamoidean ligaments (OSLs) is commonly diagnosed during magnetic resonance imaging (MRI) of the equine distal limb. Presence of striations within the ligament and magic angle artefact can result in an incorrect diagnosis of pathological change. No studies have been performed using histopathology, the gold standard, to corroborate their imaging diagnosis. OBJECTIVES (a) To determine which MRI characteristics are associated with normal vs abnormal OSLs and (b) to evaluate the ability of MRI to correctly identify abnormal vs normal oblique sesamoidean ligaments using histopathology as the gold standard. STUDY DESIGN Observational, cross-sectional study. METHODS Cadaver limbs (n = 77) were obtained from horses (n = 21) subjected to euthanasia at the hospital. MRI and histopathology was performed on each of the limbs. MRI scoring was performed for multiple MRI characteristics, and each limb was deemed normal or abnormal. Histopathology scoring was performed to give an overall score of normal or abnormal. Mixed model logistic regression was performed to evaluate which MRI characteristics were associated with normal vs abnormal OSLs using backwards elimination and a significance level of

BACKGROUND: Chondromalacia of the cranial medial femoral condyle (CMFC) is a potential cause of stifle lameness in adult horses. However, there is scant published evidence of either its occurrence or its clinical significance. OBJECTIVES: To document the occurrence of CMFC seen during diagnostic arthroscopy in adult horses with stifle lameness and to investigate its prognostic significance. STUDY DESIGN: Retrospective cohort study. METHODS: The records were reviewed of all horses with unilateral or bilateral lameness localised to the stifle that underwent diagnostic arthroscopy of the cranial medial femorotibial joint at a UK equine hospital. The surgical findings were noted from each. Case outcomes were determined by unstructured telephone discussions with owners. A satisfactory outcome was defined as a horse that was in ridden work without ongoing anti‐inflammatory medication. Multivariable logistic regression was used to create a model with an outcome time point at 12‐month post‐operatively. RESULTS: One hundred and four horses were included in the study. CMFC was found in 79. In 25 CMFC was the only finding, 54 horses had CMFC plus other pathology and 25 had other pathology, but no CMFC. At 12 months, horses with CMFC were 9.9 (95% CI 2.2–45.0, P

BACKGROUND: Pathology of the digital flexor tendon sheath is a significant cause of lameness in the horse. Imaging is important to identify lesions and inform on prognosis prior to tenoscopic surgery. OBJECTIVES: To use a large population to evaluate 1) the sensitivity and specificity of digital flexor tendon sheath (DFTS) contrast radiographs in diagnosing manica flexoria (MF) tears, deep digital flexor tendon (DDFT) tears and constriction of the palmar/plantar annular ligament (PAL) using novel criteria; 2) predisposition to pathology in signalment and limb affected. STUDY DESIGN: Multicentre retrospective cohort study. METHODS: The medical records of 206 horses with lameness localised to the DFTS, contrast radiographs and subsequent tenoscopic surgery were reviewed. Breed and limb predispositions were evaluated for pathology of the DDFT, MF and PAL constriction. Contrast radiographs of the DFTS were reviewed by four masked operators and for each pathology the sensitivity, specificity and interobserver variability were calculated. RESULTS: Contrast tenography was a sensitive test for MF tears (92% confidence interval [CI] 88.4–94.4%; specificity 56%, CI 51.1–61.1%) and specific for diagnosing DDFT tears (73%, CI 68.6–76.8%; sensitivity 54%, CI 47.8–60.2%) but had a lower sensitivity (71%, CI 65.1–75.9%) and specificity (45%, CI 39.1–52.0%) for PAL constriction. It had good to substantial interobserver agreement for MF and DDFT tears (Krippendorff's alpha 0.68 and 0.46 respectively). Ponies (57%) and cobs (58%) were significantly more likely to be affected with MF tears (other breeds 20–39%, P = 0.003) and Thoroughbreds (50%), warmbloods (45%) and draught breeds (48%) were more likely to have DDFT tears (other breeds 22–34%, P = 0.01). MF tears and PAL constriction were overrepresented in the hindlimbs compared to DDFT tears in forelimbs. MAIN LIMITATIONS: No standardisation of contrast radiographs was possible. The subjectivity of diagnosis of PAL constriction may also have led to bias. Radiographs were read as JPEGS reducing ability to manipulate images. CONCLUSIONS: Contrast radiography of the DFTS is accurate in the pre‐operative diagnosis of DFTS pathologies. Different pathologies are overrepresented in certain breeds and limbs.

Background: Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking. Objectives: We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neoepitope in the synovial fluid from the joints of healthy horses and those with different stages of OA. Study design: In vitro quantitative proteomics and assay development with application in synovial fluids samples obtained from biobanks of well-characterised horses. Methods: Articular cartilage explants were incubated with or without interleukin-1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid was obtained from either normal joints (n = 15) or joints causing lameness (n = 17) or with structural OA lesions (n = 7) and analysed for concentrations of the COMP neoepitope using a custom-developed inhibition enzyme-linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neoepitopes. Results: Semitryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neoepitope of the N-terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition ELISA was developed to quantify the COMP neoepitope in synovial fluid. The mean concentration of the COMP neoepitope significantly increased in the synovial fluid from the joints responsible for acute lameness compared with normal joints and the joints of chronically lame horses and in joints with chronic structural OA. Immunolabelling for the COMP neoepitope revealed a pericellular staining in the interleukin-1β-stimulated explants. Main limitations: The ELISA is based on polyclonal antisera rather than a monoclonal antibody. Conclusions: The increase in the COMP neoepitope in the synovial fluid from horses with acute lameness suggests that this neoepitope has the potential to be a unique candidate biomarker for the early molecular changes in articular cartilage associated with OA. (Less)

Reasons for performing study It has been suggested that ultrasonography is unreliable for the detection of hindlimb proximal suspensory desmopathy (PSD) based on comparison between ultrasonographic and magnetic resonance images. Objectives To compare ultrasonography with gross and histopathological post mortem examination in horses with PSD diagnosed based on the response to local anaesthesia and ultrasonography. Study design Retrospective study. Methods Nineteen horses with hindlimb PSD were humanely destroyed. The ultrasonographic abnormalities were graded prospectively as mild, moderate or severe based on predefined criteria. Thirty-seven lame limbs were examined grossly and 36 suspensory ligaments (SLs) were examined histologically. The histological images were graded blindly based on predefined criteria (0–3 for each tissue type; 0 = normal, 3 = severe abnormality). Descriptive statistics were performed. Results Ultrasonographic lesions were graded moderate in 31/38 (81.6%) and severe in 7/38 (18.4%) limbs; in 4/36 (11.1%) limbs adhesion formation between the proximal aspect of the SL and the accessory ligament of the deep digital flexor tendon was predicted. Gross post mortem examination revealed substantial adhesions between the proximal aspect of the SL and adjacent soft tissues in 10/37 (27.0%) limbs; in 10/37 (27.0%) limbs there were adhesions between the body of the SL and the mid plantar aspect of the third metatarsal bone, extending distally in 6 (16.2%) limbs. Histology revealed abnormalities (grades 1–3) of the collagenous tissue in 25/36 (69.4%) limbs. Muscle was abnormal (grades 1–3) in 35/36 (97.2%) limbs and adipose tissue (grades 1–3) in 16/36 (44.4%) limbs. Neural abnormalities (grades 1–3) were seen in 23/36 (63.9%) limbs and vascular changes (grade 1 and 2) in 2/36 (5.6%) limbs. In 1/36 limbs no abnormality was detected. Conclusions Ultrasonography was reasonably reliable for the detection of SL pathology based on histology as a gold standard, but the ability to detect gross adhesions was limited. Ethical animal research: The study was approved by the Ethical Review Committee of the Animal Health Trust and had informed consent of the owners. Source of funding: None. Competing interests: None declared.

Summary Background Molecular serum markers that can identify early reversible osteoarthritis (OA) in horses are lacking. Objectives We studied serum concentrations of a novel cartilage oligomeric matrix protein (COMP) neo‐epitope in horses subjected to short‐term exercise and with acute lameness. The effects of circadian rhythm and age were also evaluated. Study design Longitudinal studies in healthy horses and cross‐sectional comparison of lame and non‐lame horses. Methods Sera were collected from five horses before and after short‐term interval exercise and during full‐day box rest. Sera from 32 acutely lame horses were used to evaluate age‐related effects. Independent samples from control horses (n = 41) and horses with acute lameness (n = 71) were included. COMP neo‐epitope concentrations were analysed using custom‐developed inhibition ELISAs validated for equine serum. The presence of COMP neo‐epitope was delineated in healthy and osteoarthritic articular cartilage with immunohistochemistry. Results COMP neo‐epitope concentrations decreased after speed training but returned to baseline levels post‐exercise. No correlations between age and serum COMP neo‐epitope concentrations were found (r = 0.0013). The mean (±s.d.) serum concentration of COMP neo‐epitope in independent samples from non‐lame horses was 0.84 ± 0.38 μg/mL, and for lame horses was 5.24 ± 1.83 μg/mL (P

BACKGROUND: Equine diagnostic anaesthesia can be a useful tool in challenging lameness examinations. However, anaesthetics diffuse over time leading to nonspecific desensitisation of periarticular structures. Nerves that convey sensation from the distal limb to the central nervous system pass in close proximity to the caudal stifle joint capsule. Therefore, diffusion of intra-articular (IA) anaesthetics could cause inadvertent desensitisation of the distal limb resulting in a false diagnosis of stifle lameness. OBJECTIVES: To determine if IA stifle anaesthesia can alleviate lameness originating in the distal limb. STUDY DESIGN: Crossover experiment. METHODS: Nine horses were fitted with a circumferential hoof clamp to induce a moderate unilateral hindlimb lameness. Intra-articular stifle anaesthesia was performed and gait was evaluated every 10 min during the 90-min trial using an inertial sensor system. Push-off and landing components of the lameness were assessed by measuring the mean inter-stride difference between the maximum and minimum heights of the pelvis respectively. Differences were compared using a Wilcoxon signed-rank test. RESULTS: Overall, horses with hoof clamp-induced foot pain had a reduction in push-off lameness after IA stifle anaesthesia. The mean change in diffmax at 90 min was −4.3 mm (P = 0.005) for the experimental group vs. −2.3 mm (P = 0.2) for the control group. Lameness decreased over time, with an average improvement of 23% at 30 min, 33% at 60 min and 38% at 90 min. There was high inter-horse variability; 3/9 horses improved by ~50% within 30 min, while 2/9 improved by ~30% and 4/9 had minimal (

BACKGROUND: Lameness can be multifactorial and may result from the accumulation of multiple seemingly unrelated causes. The identification of factors associated with lameness could be one method to decrease incidence of lameness and prolong the equine athlete's competitive life. OBJECTIVES: To determine if there is an association between hoof balance in the sagittal plane and hindlimb lameness. STUDY DESIGN: Case‐control study. METHODS: Eighty client‐owned horses with hindlimb lameness (cases) and 80 horses with no detectable hindlimb lameness (controls) were prospectively enroled following lameness evaluation as either cases (lameness localised with regional anaesthesia) or controls (no hindlimb lameness). Lameness cases were divided based on location (stifle, tarsus, proximal metatarsus and other sites). Lateromedial radiographs were performed on hind hooves and plantar angle of the distal phalanx (PADP) was determined. The prevalence of negative/neutral PADP and median PADPs were calculated. Conditional logistic regression and Wilcoxon signed rank tests were used to analyse PADPs, and odds ratios were calculated. Significance was set at P

Background Clodronate is prescribed to performance horses with lameness. Despite its clinical popularity, little research has been done to understand the effects of clodronate in the horse. Objectives Our objective was to determine if a single treatment with clodronate at the clinically approved dose altered bone remodelling, bone cell recruitment or lameness in the horse. Study design Twelve university-owned equestrian team competition horses with a history of forelimb lameness due to navicular syndrome were randomised to receive either 1.4 mg/kg clodronate (CLOD n = 6) or an equivalent volume of LRS (CONT; n = 6) in a blinded manner. Methods Blood was evaluated weekly for 8 weeks before and after drug administration (clodronate or placebo) for bone turnover markers CTX-I and osteocalcin. Lameness evaluations were performed to assess for change in lameness 1 week before and 1, 2, 3 and 8 weeks after drug administration. Coach questionnaires were performed to assess for change in ridden performance 1, 2, 3 and 8 weeks after drug administration. Bone cell recruitment was evaluated in vitro 2 weeks before and after drug administration. Results There were no differences in in vitro bone cell recruitment from whole bone marrow or in bone turnover markers CTX-I or osteocalcin. A small but significant decrease in forelimb lameness was detected in CLOD treated horses 1 week after treatment (P = 0.005). There were no significant differences in hindlimb lameness. Coaches identified an improvement in performance significantly more often in CLOD vs. CONT (P = 0.01) at week 8. Main limitations Two CONT horses received intra-articular anti-inflammatory medication after treatment, which may have altered lameness results. Conclusions A single dose of clodronate appears to reduce lameness without producing detectable effects on bone turnover markers. Due to the long half-life of a bisphosphonate drug, the effect of multiple doses on bone remodelling and lameness should be investigated. The Summary is available in Portuguese - see Supporting Information.

Summary Reasons for performing study The high, repetitive demands imposed on polo horses in training and competition may predispose them to musculoskeletal injuries and lameness. Objectives To quantify movement symmetry and lameness in a population of polo horses, and to investigate the existence of a relationship with age. Study design Convenience sampled cross-sectional study. Methods Sixty polo horses were equipped with inertial measurement units (IMUs) attached to the poll, and between the tubera sacrale. Six movement symmetry measures were calculated for vertical head and pelvic displacement during in-hand trot and compared with values for perfect symmetry, compared between left and right limb lame horses, and compared with published thresholds for lameness. Regression lines were calculated as a function of age of horse. Results Based on 2 different sets of published asymmetry thresholds 52–53% of the horses were quantified with head movement asymmetry and 27–50% with pelvic movement asymmetry resulting in 60–67% of horses being classified with movement asymmetry outside published guideline values for either the forelimbs, hindlimbs or both. Neither forelimb nor hindlimb asymmetries were preferentially left or right sided, with directional asymmetry values across all horses not different from perfect symmetry and absolute values not different between left and right lame horses (P values >0.6 for all forelimb symmetry measures and >0.2 for all hindlimb symmetry measures). None of the symmetry parameters increased or decreased significantly with age. Conclusions A large proportion of polo horses show gait asymmetries consistent with previously defined thresholds for lameness. These do not appear to be lateralised or associated with age.

Summary Background The main criteria for lameness assessment in horses are head movement for forelimb lameness and pelvic movement for hindlimb lameness. However, compensatory head nod in horses with primary hindlimb lameness is a well‐known phenomenon. This compensatory head nod movement can be easily misinterpreted as a sign of primary ipsilateral forelimb lameness. Therefore, discriminating compensatory asymmetries from primary directly pain‐related movement asymmetries is a prerequisite for successful lameness assessment. Objectives To investigate the association between head, withers and pelvis movement asymmetry in horses with induced forelimb and hindlimb lameness. Study design Experimental study. Methods In 10 clinically sound Warmblood riding horses, forelimb and hindlimb lameness were induced using a sole pressure model. The horses were then trotted on a treadmill. Three‐dimensional optical motion capture was used to collect kinematic data from reflective markers attached to the poll, withers and tubera sacrale. The magnitude and side (left or right) of the following symmetry parameters, vertical difference in minimum position, maximum position and range‐up were calculated for head, withers, and pelvis. Mixed models were used to analyse data from induced forelimb and hindlimb lameness. Results For each mm increase in pelvic asymmetry in response to hindlimb lameness induction, withers movement asymmetry increased by 0.35–0.55 mm, but towards the contralateral side. In induced forelimb lameness, for each mm increase in head movement asymmetry, withers movement asymmetry increased by 0.05–0.10 mm, in agreement with the head movement asymmetry direction, both indicating lameness in the induced forelimb. Main limitations Results must be confirmed in clinically lame horses trotting overground. Conclusions The vertical asymmetry pattern of the withers discriminated a head nod associated with true forelimb lameness from the compensatory head movement asymmetry caused by primary hindlimb lameness. Measuring movement symmetry of the withers may, thus, aid in determining primary lameness location.

BACKGROUND Systemic administration of gadolinium contrast medium is common in small animals to increase lesion conspicuity and determine vascularisation of lesions identified with magnetic resonance imaging (MRI); however, the large volume required for systemic administration limits its use in horses. OBJECTIVES The purpose of this study was to assess the feasibility of administering a low dose of contrast medium via venous regional limb perfusion. STUDY DESIGN Prospective clinical study. METHODS Distal limbs of 26 horses (one limb per horse) were imaged with MRI before and after administration of 5 mL of gadopentetate dimeglumine (Magnevist® ) diluted with 5 mL of physiological saline via a palmar/plantar digital vein with a tourniquet in place at the level of the mid aspect of the third metacarpal/metatarsal bone. Commonly assessed structures of the equine distal limb were examined for normal and abnormal contrast enhancement. RESULTS Twenty-five of 26 horses had adequate contrast enhancement of their distal limb. The lack of adequate contrast enhancement in one limb was likely associated with failure of the tourniquet. No adverse reactions were identified in any horse. One hundred thirty-two lesions were detected, of which, 69 contrast enhanced. Twelve lesions were detected exclusively following contrast enhancement. MAIN LIMITATIONS Case numbers and lesion variability yielded insufficient data to perform statistical analyses. Histopathology was not performed on sound horses to determine if the imaged structures were normal. CONCLUSIONS Regional limb perfusion is a feasible method to administer gadolinium contrast material to the equine distal limb for MRI. The enhancement pattern of the equine distal limb in sound horses is described. Contrast enhanced MRI of the distal equine limb helps to further characterise lesions identified with precontrast images, including adhesions and deep digital flexor tendinopathy. Contrast enhanced MRI also aids in identification of additional lesions, such as neovascularisation.

SummaryReasons for performing study Saddle slip is usually blamed on saddle fit, crooked riders or horse shape, but may reflect hindlimb lameness. There are no studies of the frequency of occurrence of saddle slip and risk factors within a tested sample population of the general sports horse population. Objectives To quantify the frequency of saddle slip and to describe the association with lameness, thoracolumbar shape/symmetry, crooked riders and ill-fitting saddles. Study design Nonrandom, cross-sectional survey using convenience sampling. Methods Five hundred and six sports horses in normal work were assessed prospectively. Thoracolumbar shape/symmetry were measured at predetermined sites; the presence of lameness (in hand and/or ridden) and saddle slip was recorded. Descriptive statistics, univariable and multiple logistic regression were performed to assess the relationship between horse–saddle–rider factors and saddle slip. Results The frequency of lameness, quadrilaterally reduced cranial phase of the stride or stiff, stilted canter was 45.7%, saddle slip 12.3%, left–right thoracolumbar shape asymmetries ≥ coefficient of variance of 8% (1.2 cm) 0.6%; and 103 of 276 riders (37.3%) sat crookedly. The saddle consistently slipped to one side in 24.4% of horses with hindlimb lameness alone, 45.5% of horses with concurrent hindlimb and forelimb lameness, compared with 5.4% with forelimb lameness, 17.4% with stiff, stilted canter, 20% with quadrilaterally reduced cranial phase of stride and 5.5% nonlame horses. Nineteen horses (30.6%) with saddle slip had no detectable hindlimb lameness; however, 14 had a gait abnormality, particularly in canter. Multivariable analysis revealed that saddle slip was significantly associated with hindlimb lameness and gait abnormalities (odds ratio [OR] = 52.62, 95% confidence interval [CI] 17.3–159.7), a saddle fitted with even contact and uniform flocking (OR = 15.49, 95% CI 1.9–125.5), riders sitting crookedly (OR = 6.32, 95% CI 2.9–13.7), a well-balanced saddle (OR = 3.05, 95% 1.4–6.9) and large back shape ratio at T18 (OR = 1.2, 95% 1.1–1.3). Conclusions Many horses with hindlimb and/or forelimb lameness go unrecognised. Saddle slip may be a sign of hindlimb lameness. Education of the equestrian population to identify lameness and saddle slip is required. The Summary is available in Chinese – see Supporting information.

Summary Reasons for performing the study Lameness is prevalent in working donkeys and has major welfare implications; however, a detailed study of the associated clinical signs is lacking. Objectives To describe the range and prevalence of clinical signs and conformation associated with lameness in working draught donkeys. Study design Prospective, cross-sectional, observational study. Methods Data were collected from 102 working draught donkeys in Pakistan. A lameness assessment adapted for working donkeys was used to record clinical signs of lameness, gait, limb conformation and pain responses in the feet, limbs and spine using observation, palpation and manipulation. Lameness at the walk was scored from 0 to 10 (sound to nonweightbearing). Results Every donkey examined had gait abnormalities, with 5% having a nonweightbearing limb. Lameness was significantly more severe with older age, lower body condition score and forward-at-the-knee conformation. More severe lameness was also associated with pain responses in the hoof walls, palpation of limb joints and spinal flexion. Joint, tendon and foot pathology was highly prevalent, as well as pain responses to joint flexion and spinal manipulation. Conformational abnormalities showed lateral asymmetries. Conclusions Over 98% of the world's 42.2 million donkeys are in low-income countries, most being used for work. The high prevalence of lameness, pain and multiple limb and spinal abnormalities in working donkeys is of great welfare concern and highlights the complexity of addressing this problem. This standardised lameness assessment can be used when implementing and monitoring interventions to reduce lameness prevalence in working donkeys.

SummaryReasons for performing study Subjective evaluation of the response to diagnostic analgesia of hindlimb lameness is influenced by expectation bias. Quantification of pelvic movement with inertial measurement units is possible, but it is unclear which measure of movement symmetry best reflects the changes seen after diagnostic analgesia. Objectives To test our hypothesis that objective measures closely relating to those used for subjective visual lameness scoring (quantifying the difference between sacral upward or downward movement or between movement amplitudes of the left and right tubera coxae) would show the largest and most consistent response. Study design Retrospective analysis of subjective and objective clinical lameness data. Methods Thirteen horses with hindlimb lameness underwent visual lameness scoring and independent gait assessment with inertial measurement units. Established objective measures were calculated and changes before/after diagnostic analgesia regressed against the change in lameness grade. Slopes of regression lines were calculated and confidence intervals assessed. Results All objective parameters showed variation between horses and across lameness grades. The following 3 measures documented a consistent increase in symmetry for each grade of change in lameness score: difference between sacral displacement minima; upward movement difference; and range of motion difference between the tubera coxae. Conclusions Several pelvic parameters are suitable for objective quantification of changes after diagnostic analgesia in hindlimb-lame horses. A change of 9–13% per lameness grade can be expected. Upward movement of the tubera coxae is the most sensitive objective measure for quantifying a response to diagnostic analgesia. However, when assessed visually, this measure requires simultaneous focusing on pelvic and limb movements. Other parameters that show a similar response might be more easily perceived, requiring only assessment of tubera coxae range of motion or downward displacement of the sacrum without simultaneous focus on limb movement.

Background Injury to the proximal suspensory ligament is a common cause of lameness in cutting horses. Radiographic and ultrasonographic imaging of lesions responsible for lameness can provide ambiguous results. MRI provides the most comprehensive diagnostic imaging evaluation of lesions specifically affecting cutting horses. Objectives To describe the distribution and severity of bone and soft tissue lesions present in the proximal metacarpus of Quarter Horse cutting horses and to assess the impact of these lesions on return to competition. Study design Retrospective case series. Methods Retrospective analysis of 32 cutting horses referred for MRI of the proximal metacarpus between 2009 and 2012 with a 2-year follow-up period. MRI studies were evaluated by a board-certified veterinary radiologist; the severity of lesions was graded from 0 (absent) to 3 (severe). Results A total of 20 right and 24 left forelimbs (12 bilateral studies) of 32 horses were evaluated. The most common findings were: third metacarpal (McIII) sclerosis at the proximal suspensory ligament (PSL) origin (42/44), McIII resorption at the PSL origin (32/44), PSL dorsal margin fibre irregularity (30/44) and McIII bone contusion (22/39). Of the 30 horses, 22 horses successfully returned to competition, irrespective of severity of injury. Strong correlation exists between the degree of resorption in the palmar cortex of proximal McIII, degree of McIII sclerosis and severity of dorsal margin fibre irregularity. Main limitations Statistical significance was limited by small study population. Further analysis of prognosis was limited by availability of comprehensive medical records. Conclusions Cutting horses with proximal metacarpal pain have significant pathological change within the proximal suspensory ligament and its enthesis on the palmar cortex of McIII. Severity of lesions and degree of lameness at the time of diagnosis does not influence return to performance. Accurate diagnosis of proximal metacarpal lesions based on MRI offers clinicians the capacity to select treatment protocols targeted to each disease process.

Summary A method is described for the estimation of joint moments of force and power in the equine forelimb using S-VHS video and force platform data. Video and force data were collected for 5 walking trials in a sound Dutch Warmblood horse. The sagittal plane positional and angular data were combined with the vertical and cranio-caudal ground reaction forces to calculate net joint moments of force in the sagittal plane across the carpal, fetlock and coffin joints during the stance phase of the forelimb. The mechanical power was calculated as the product of the net joint moment and the joint's angular velocity. The carpus demonstrated oscillating periods of energy generation and absorption in early stance against a flexor moment, then an absorption phase at the end of stance as the carpus flexed against an extensor moment. The fetlock absorbed energy in early stance as it flexed against an extensor moment, then showed short periods of positive and negative work in mid-stance. Energy was generated across the fetlock as it extended for push-off. An extensor moment was measured at the coffin joint through most of stance, and this coincided with a phase of energy absorption followed by a longer phase of generation. In terminal stance, a flexor moment was produced and this was accompanied by a period of generation for push-off.

Clinical experience continues to expand our understanding of the pathophysiology of pain and injury within the carpal joints. The anatomical and physiological capacity of the equine carpus to neutralise loading stress plays a significant role in the prevention of carpal injury. The ability of joint surfaces to dissipate axial force by transfer to the interosseous ligaments is the principal means by which carpal injury is avoided. In the medial aspect of the intercarpal joint and the dorsal aspect of the radial carpal joint, however, the effects of chronic maximal stress and isolated acute supraphysiological loads cannot be neutralised. Progressive osseous remodelling and stress induced changes within the bone, which outstrip its ability to accommodate increasing loads, lead to the loss of structural integrity and fracture in horses in training.

The effect of alimentary carbohydrate overload on hoof temperature was investigated to determine the state of the sublamellar vasculature preceding the onset of equine laminitis. Hoof, core and ambient temperatures and heart rate were logged continuously in 21 mature Standardbred horses kept in an environmental chamber set at 10 degrees C. Recording hoof temperature was a successful, noninvasive, method to measure indirectly, shifts in digital blood flow against a background of cold induced, physiological, vasoconstriction. High hoof temperatures were assumed to indicate digital vasodilation and low hoof temperatures digital vasoconstriction. Seven horses were either untreated or sham treated controls. A slurry of ground wheat flour (17.5 g/kg) was administered via nasogastric tube to 13 horses all of which were humanely killed 48 h later. Histological sections of the lamellar tissues were examined for evidence of laminitis. Analysis of mean hoof temperature graphs showed that horses judged laminitis positive had experienced a period of prolonged digital vasodilation 16-40 h after carbohydrate overload. Laminitis negative horses experienced no such period of vasodilation and never had hoof temperatures significantly (except once, at 28 h) above that of controls. The only parameter which significantly differentiated the laminitis positive from laminitis negative horses, between 12 and 32 h after carbohydrate overload, was foot temperature, which was significantly higher in laminitis positive horses (P < 0.05). Therefore, a period of sublamellar vasodilation, 12 to 40 h after alimentary carbohydrate overload precedes the onset of laminitis. If the digital circulation sustains vasoconstriction during this period then laminitis does not occur. We propose that the period of increased digital blood flow in laminitis positive horses, concomitant with the severe metabolic crisis brought on by the alimentary carbohydrate overload, may expose the lamellar tissues to a concentration of blood borne factors sufficient to trigger lamellar separation.

Summary Nuclear scintigraphy was used to assess digital perfusion before and after treatment in 10 horses with clinical and radiographic evidence of chronic laminitis. Horses were evaluated for lameness, degree of distal phalanx rotation, and heel-toe hoof wall growth ratio, and randomly divided into two treatment groups. Group 1 horses received only egg bar-heart bar shoeing; Group 2 underwent egg bar-heart bar shoeing and coronary grooving. Horses were re-evaluated for digital perfusion, lameness, degree of distal phalanx rotation, and hoof wall growth at 6 week intervals over the 18 week follow-up period. Prior to treatment, relative scintigraphic activity at the dorsal laminar area was decreased and relative scintigraphic activity at the toe and adjacent solar area was increased. Egg bar-heart bar shoeing was associated with significantly increased dorsal laminar scintigraphic activity and significantly decreased solar scintigraphic activity over the 18 week period. Coronary grooving, in combination with egg bar-heart bar shoeing, resulted in a significantly lower heel-toe hoof wall growth ratio but did not enhance digital perfusion. Seven of 10 (70%) horses were responsive to treatment, defined as an improvement in lameness by at least one grade. Horses that were refractory to treatment had significantly lower dorsal laminar scintigraphic activity and higher palmar coronary scintigraphic activity prior to treatment than horses that responded to treatment. Our results are the first to demonstrate that egg bar-heart bar shoeing is associated with improved dorsal laminar perfusion, and support the use of this technique. In addition, we found that pre-treatment nuclear scintigraphy was predictive of clinical outcome in horses with chronic laminitis treated with corrective shoeing.

Summary Force plate data from walking horses were used to evaluate the locomotion of a group of six horses during experimentally induced lameness in a forelimb or a hindlimb. By tightening or loosening screws in modified horseshoes the resulting pressure pain on the sole enabled induction and release of three different degrees of supporting lameness within a period of 2 h. The ground reaction force (GRF) patterns of the different recording sessions were compared with control data of the same horse as well as with the ‘standard’ horse data using a quantitative evaluation procedure involving 93 GRF parameters. Clinically mild and moderate lameness at the walk could be distinguished by applying the H(orse)INDEX method, using ‘standard’ GRF data of horses of the same breed. Even subtle changes (clinically mild lameness at the trot but no lameness visible at the walk, and nerve blocking of moderate lameness at the walk) could be demonstrated objectively using an adapted quantification procedure (the C(ontrol)INDEX method), if control GRF parameters of that horse were obtained before lameness was present.

Injury of the lateral collateral ligaments of the tarsocrural joints was diagnosed in nine Standardbred pacers. The average age was 4.9 years. The severity of the lameness varied from severe to subtle and joint effusion was seen in eight of 10 tarsocrural joints. A positive hindlimb flexion test was seen in four of six cases in which results were recorded. The identification of the site of involvement was based on a focal intense 'hot spot' seen on scintigraphy, and new bone formation seen radiographically at the anatomical sites of insertion of the long lateral collateral ligament of the tarsocrural joint in nine limbs and the short lateral collateral ligament of one limb. The authors believe this injury to be enthesitis caused by the cyclic trauma of training and racing speed. The primary therapy was rest. Of six cases which returned to training, three raced as well or better than before injury.

Summary Reasons for performing study: Causes of palmar foot pain and the aetiopathogenesis of navicular disease remain poorly understood, despite the high incidence of foot-related lameness. Hypotheses: Abnormalities of the deep digital flexor tendon (DDFT) may contribute to palmar foot pain; ageing degenerative changes may be seen in horses free from lameness; and horses with lameness are likely to have a greater severity of abnormalities than age-matched horses with no history of foot pain. Methods: Feet were selected from horses with a history of uni- or bilateral forelimb lameness of at least 2 months' duration. Histology of the DDFT from the level of the proximal interphalangeal joint to its insertion were examined and the severity of lesions for each site graded. Associations between lesions of the navicular bone, collateral sesamoidean ligaments (CSL), distal sesamoidean impar ligament, navicular bursa, distal interphalangeal (DIP) joint synovium and collateral ligaments of the DIP joint and DDFT were assessed. Results: There was no relationship between age and grade of histological abnormality of the DDFT. There were significant histological differences between groups for lesions of the dorsal layers of the DDFT, but not for lesions of the palmar aspect. There were significant associations between histological grades for the superficial dorsal layer of the DDFT and flexor aspect of the navicular bone; and between the deep dorsal layer of the DDFT and the proximal border and medulla of the navicular bone. The navicular bursa grade was correlated with grades for the superficial dorsal, deep dorsal and deep palmar layers of the DDFT. The histological grades for the CSL and the superficial dorsal layer of the DDFT were also associated. Conclusions: Pathological abnormalities in lame horses often involved the DDFT in addition to the navicular bone. Vascular and matrix changes may precede changes in the fibrocartilage of the navicular bone. Potential relevance: Identification of factors leading to vascular changes within the interstitium of the DDFT and changes in matrix composition, may help in future management of palmar foot pain.

The superficial digital flexor tendon (SDFT) is an elastic structure that during maximal exercise appears to operate close to its functional limits. The biomechanical and biochemical responses to exercise, injury, and healing are still poorly understood but ongoing research is providing valuable new information which is addressed in this review. It appears that the SDFT matures early, after which time it has limited ability to adapt to stress and undergoes progressive degeneration. Focal hypocellularity, collagen fibril degeneration, selective fibril loading and alterations in the noncollagenous matrix occur primarily within the central core region of the midmetacarpal segment. Current treatment strategies have had equivocal results in returning animals to optimal athletic activity. To date it would seem that progressive rehabilitation programmes coupled with regular ultrasonographic evaluations are a cost-effective and comparable strategy when compared to surgical treatment methods. Recent interest in pharmacological modulation of intrinsic healing of collagenous structures has led to the investigation of various growth factors as potential therapeutic aids in the healing of tendon injuries. However, one of the major goals in tendon research, and one which holds the most optimism for success in the immediate future, is the prevention of tendon injuries.

Summary Reasons for performing study: Previous studies have implicated tension in the deep digital flexor tendon (DDFT) in the rotation of the distal phalanx (DP) after the breakdown of the dorsal laminae caused by laminitis. Howeveer, once the DP has rotated, the DDFT should become shorter, reducing the force it exerts on the DP. Objective: To compare DDFT force and ground reaction forces (GRFs) in normal ponies and ponies with rotation of the DP as a sequel to laminitis. Methods: Six normal ponies (Group 1) and 6 sound ponies with 6-13° of rotation of the DP in relation to the dorsal hoof wall (Group 2) were assessed at trot using forceplate and motion analysis. The force in the DDFT was calculated by assuming that the extending moment at the distal interphalangeal (DIP) joint resulting from the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase (inverse dynamics). Results: In early stance, the peak DDFT force (mean ± s.d.) in the normal ponies was 1.92 ± 1.63 N/kg. However, in Group 2, the point of zero moment was palmar to the centre of rotation of the DIP joint for the first 40% of stance and hence DDFT force was zero. Force in the DDFT reached a peak of 10.00 ± 3.56 N/kg at 60.7 ± 5.6% of stance in Group 1 and 6.41 ± 1.37 N/kg at 79.2 ± 9.6% of stance in Group 2. Conclusions: DDFT force in Group 2 laminitic ponies was much reduced until late stance, when it neared normal values. Potential relevance: Further studies of ponies with rotation of the DP as a sequel to laminitis should assist farriery aimed at reducing the force in the DDFT through the breakover phase of stance to protect damaged dorsal laminae.