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Background: Osteoarthritis of the medial tibiofemoral joint (MTFJ) is prevalent among patients undergoing anterior cruciate ligament reconstruction (ACLR). Magnetic resonance T1ρ and T2 relaxation times provide noninvasive methods to quantify early cartilage degeneration. Altered sagittal-plane gait biomechanics have been observed after ACLR, but their associations with longitudinal changes in MTFJ cartilage T1ρ and T2 remain unclear. Hypothesis/Purpose: To examine whether the peak knee flexion moment (KFM), knee flexion angle (KFA), and vertical ground-reaction force (vGRF) during gait are associated with prospective changes in medial tibiofemoral cartilage T1ρ and T2 in ACL-reconstructed knees and to compare these gait characteristics between patients undergoing ACLR and healthy control participants. We hypothesized that a higher KFM, KFA, and vGRF would be associated with greater increases in cartilage relaxation times and that patients undergoing ACLR would demonstrate altered gait characteristics compared with healthy controls. Study Design: Controlled laboratory study. Methods: Thirty-three patients undergoing ACLR underwent gait analysis before and 6 months and 1 year after ACLR and knee magnetic resonance imaging (MRI) before and 6 months, 1 year, and 2 years after ACLR. Twelve healthy controls underwent knee MRI and gait analysis at baseline and 1 year. Cartilage T1ρ and T2 were calculated for the medial tibia and medial femoral condyle. Linear regressions were used to evaluate associations between gait characteristics and changes in cartilage relaxation times from before ACLR to follow-up time points. Independent t tests were used to compare differences in gait between patients undergoing ACLR and control participants. Results: A higher KFM and KFA before ACLR were related to greater increases in medial femoral condyle T1ρ and T2 at 6 months after ACLR. Similarly, a higher KFM, KFA, and vGRF at 6 months were associated with greater increases in medial tibia and medial femoral condyle T1ρ and T2 at 1 and 2 years after ACLR. Gait characteristics at 1 year were not associated with changes in cartilage relaxation times at 2 years after ACLR. Compared with healthy controls, patients undergoing ACLR demonstrated a lower KFM at 6 months after ACLR. Conclusion/Clinical Relevance: The findings of this study revealed that a higher KFM, KFA, and vGRF during gait, especially at 6 months after ACLR, were associated with greater deterioration of MTFJ cartilage health at later time points. [ABSTRACT FROM AUTHOR]

Purpose Quantification of knee motion is essential for assessment of pathologic joint function, such as tracking osteoarthritis progression and evaluating outcomes after conservative or surgical treatment, including total knee arthroplasty. Our purpose was to establish a useful baseline for the kinematic envelope of knee motion in healthy older adults performing movements of daily living. Methods A high-speed stereo radiography system was used to measure the three-dimensional tibiofemoral kinematics of eight healthy people over 55 yr of age (4 women/4 men; age, 61.7 ± 5.4 yr; body mass, 74.6 ± 7.7 kg; body mass index, 26.7 ± 4.4 kg·m-2; height, 168.2 ± 13.7 cm) during seated knee extension, level walking, pivoting, and step descent. Results Internal--external and varus--valgus rotation and anterior--posterior range of motion through stance in normal walking averaged 3.6° ± 1.1°, 2.3° ± 0.6°, and 3.4 ± 1.57 mm, respectively. Average range of motion across subjects was greater during the step-down in both internal--external rotation (average, 6.5° ± 3.1°) and anterior--posterior translation (average, 4.5 ± 1.1). Average internal--external range of motion increased to 13.5° ± 3.6° during pivoting. Range of motion of the knee in varus--valgus rotation was nearly the same for each subject across activities, rarely exceeding 6°. Conclusions Pivoting and step descending during walking had greater internal--external rotation and anterior--posterior translation than normal gait. Internal--external rotation and anterior--posterior translation were shown to have greater activity dependence, whereas varus--valgus rotation was consistent across activities. These results were similar to prior measurements in younger cohorts, though a trend toward reduced range of motion in the older adults was observed. [ABSTRACT FROM AUTHOR]

ABSTRACT This study calculated the frequency of occurrence of gap imbalances between medial and lateral compartments at 0° flexion and within a compartment between 0° and 90° flexion, and changes in limb and knee alignment from native after computer simulation of total knee arthroplasty (TKA) with the knee set in 5° or 7° valgus at 0° flexion. TKA was simulated on 49 3D bone models of native limbs. At 0° flexion, the femoral component was set in 5° or 7° valgus from the anatomic axis of the femur, and the tibial component was set 0° to the tibial anatomic axis. At 90° flexion, internal-external rotation of the femoral component was set perpendicular to the anteroposterior axis of the trochlear groove (Method 1), parallel to the transepicondylar axis (Method 2), 3° externally rotated to the posterior condylar axis (Method 3), and gap-balanced to the tibial resection at 0° flexion (Method 4). For 5° and 7° valgus knees, the frequency of occurrence of TKAs (1) with ≥2 mm gap imbalance between compartments at 0° flexion was ≥49%, (2) with ≥2 mm gap imbalance within a compartment between 0° and 90° flexion ranged from 43-69% for Methods 1, 2, and 3, and (3) with ≥2° change in limb and knee alignment from native was ≥47%. Achieving balanced gaps between compartments at 0° flexion may often require soft tissue release. Unbalanced gaps within a compartment between 0° and 90° flexion represent a potential instability which is difficult to surgically correct. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2031-2039, 2017. [ABSTRACT FROM AUTHOR]

ABSTRACT Increased varus-valgus laxity has been reported in individuals with knee osteoarthritis (OA) compared to controls. However, the majority of previous investigations may not report truly passive joint laxity, as their tests have been performed on conscious participants who could be guarding against motion with muscle contraction during laxity evaluation. The purpose of this study was to investigate how a measure of passive knee laxity, recorded when the participant is under anesthesia, is related to varus-valgus excursion during gait, clinical measures of performance, perceived instability, and self-reported function in participants with severe knee OA. We assessed passive varus-valgus knee laxity in 29 participants (30 knees) with severe OA, as they underwent total knee arthroplasty (TKA). Participants also completed gait analysis, clinical assessment of performance (6-min walk (6 MW), stair climbing test (SCT), isometric knee strength), and self-reported measures of function (perceived instability, Knee injury, and Osteoarthritis Outcome Score (KOOS) a median of 18 days before the TKA procedure. We observed that greater passive varus-valgus laxity was associated with greater varus-valgus excursion during gait ( R2 = 0.34, p = 0.002). Significant associations were also observed between greater laxity and greater isometric knee extension strength ( p = 0.014), farther 6 MW distance ( p = 0.033) and shorter SCT time ( p = 0.046). No relationship was observed between passive varus-valgus laxity and isometric knee flexion strength, perceived instability, or any KOOS subscale. The conflicting associations between laxity, frontal excursion during gait, and functional performance suggest a complex relationship between laxity and knee cartilage health, clinical performance, and self-reported function that merits further study. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1644-1652, 2017. [ABSTRACT FROM AUTHOR]

Objective: To determine compartment-specific loading patterns during gait, quantified as joint reaction forces (JRF), of individuals with knee articular cartilage defects (ACD) compared to healthy controls (HC).Methods: Individuals with ACDs and HC participated. Individuals with ACDs were divided into groups according to ACD location: PF (only a patellofemoral ACD), TF (only a tibiofemoral ACD), and MIX (both PF and TF ACDs). Participants underwent three-dimensional gait analysis at self-selected speed. TF joint reaction force (TF-JRF) was calculated using inverse dynamics. PF joint reaction force (PF-JRF) was derived from estimated quadriceps force (FQUAD) and knee flexion angle. Primary variables of interest were the PF- and TF-JRF peaks (body weight [×BW]). Related secondary variables (gait speed, quadriceps strength, knee function, activity level) were evaluated as covariates.Results: First peak PF-JRF and TF-JRF were similar in the TF and MIX groups (0.75-1.0 ×BW, P = 0.6-0.9). Both peaks were also similar in the PF and HC groups (1.1-1.3 ×BW, P = 0.7-0.8), and higher than the TF and MIX groups (P = 0.004-0.02). For the second peak PF-JRF, only the HC group was higher than the TF group (P = 0.02). The PF group walked at a similar speed as the HC group; both groups walked faster than the TF and MIX groups (P < 0.001). With gait speed and quadriceps strength as covariates, no differences were observed in JRF peaks.Conclusions: The results suggest the presence of a TF ACD (TF and MIX groups), but not a PF ACD (PF group), may affect joint loading patterns during walking. Walking slower may be a protective gait modification to reduce load. [ABSTRACT FROM AUTHOR]

Runners do not have a greater prevalence of knee osteoarthritis (OA) than nonrunners. The hypothesis that joint loads in running do not cause OA is forwarded. Two mechanisms are proposed: 1) cumulative load, which is surprisingly low in running, is more important for OA risk than peak load, and 2) running conditions cartilage to withstand the mechanical stresses of running. [ABSTRACT FROM AUTHOR]

Purpose: To prospectively compare patellofemoral and tibiofemoral articulations in the upright weight-bearing position with different degrees of flexion using CT in order to gain a more thorough understanding of the development of diseases of the knee joint in a physiological position.Materials and Methods: CT scans of the knee in 0°, 30°, 60° flexion in the upright weight-bearing position and in 120° flexion upright without weight-bearing were obtained of 10 volunteers (mean age 33.7 ± 6.1 years; range 24-41) using a cone-beam extremity-CT. Two independent readers quantified tibiofemoral and patellofemoral rotation, tibial tuberosity-trochlear groove distance (TTTG) and patellofemoral distance. Tibiofemoral contact points were assessed in relation to the anteroposterior distance of the tibial plateau. Significant differences between degrees of flexion were sought using Wilcoxon signed-rank test (P < 0.05).Results: With higher degrees of flexion, internal tibiofemoral rotation increased (0°/120° flexion; mean, 0.5° ± 4.5/22.4° ± 7.6); external patellofemoral rotation decreased (10.6° ± 7.6/1.6° ± 4.2); TTTG decreased (11.1 mm ±3.7/-2.4 mm ±6.4) and patellofemoral distance decreased (38.7 mm ±3.0/21.0 mm ±7.0). The CP shifted posterior, more pronounced laterally. Significant differences were found for all measurements at all degrees of flexion (P = 0.005-0.037), except between 30° and 60°. ICC was almost perfect (0.80-0.99), except for the assessment of the CP (0.20-0.96).Conclusion: Knee joint articulations change significantly during flexion using upright weight-bearing CT. Progressive internal tibiofemoral rotation leads to a decrease in the TTTG and a posterior shift of the contact points in higher degrees of flexion. This elucidates patellar malalignment predominantly close to extension and meniscal tears commonly affecting the posterior horns. [ABSTRACT FROM AUTHOR]

Congenital anterior tibiofemoral subluxation is an extremely rare disorder. All reported cases accompanied by other abnormalities and syndromes. A 16-year-old high school girl referred to us with bilateral anterior tibiofemoral subluxation as the knees were extended and reduced at more than 30 degrees flexion. Deformities were due to tightness of the iliotibial band and biceps femuris muscles and corrected by surgical release. Associated disorders included bilateral anterior shoulders dislocation, short metacarpals and metatarsals, and right calcaneuvalgus deformity.

Background Knee osteoarthritis is one of the most debilitating diseases associated with aging, and is estimated to affect 9% of men and 18% of women over 65 years of age. Knee osteoarthritis affects the condylar surfaces of the joint and if left untreated generally leads to the slow and painful degeneration of the joint and surrounding structures. With few non-invasive treatment options for osteoarthritis patients, this study investigated the effect of therapeutic taping on knee pain in combination with spatiotemporal, kinematic, kinetic and muscle activation measures. Methods Fifteen participants (10 male, 5 female) with radiographic diagnosed knee osteoarthritis attended a single testing session and walked along at a self-selected pace under three different conditions (no tape, sham tape, therapeutic tape). The conditions were randomised within each testing session. Knee pain, lower limb biomechanics and muscle activation were analysed using a one-way repeated measures ANOVA to determine if any differences existed between the three taping conditions (α = 0.05). Findings Therapeutic knee taping was shown to significantly reduce the self-reported levels of knee joint pain during straight line walking. No significant differences in spatiotemporal, knee kinetic, knee kinematic or lower limb muscle activation variables were observed between the taping conditions. Interpretation There is evidence supporting the use of therapeutic knee taping for the management of osteoarthritis related knee pain. Future research is recommended to better understand the complex acute neuro-musculoskeletal adaptations that explain these positive knee pain findings. [ABSTRACT FROM AUTHOR]

Background: Tibiofemoral dislocation after total knee arthroplasty (TKA) is a rare complication. Published case reports describe fewer than 6 patients, making conclusions about the etiology, epidemiology, complications, and treatment of tibiofemoral dislocation difficult. This case series highlights common demographic features, potential causes, and difficulties during the management of tibiofemoral dislocations after TKA.Methods: Between 2005 and 2014, 14 patients presented to our institution with a tibiofemoral dislocation. Patients were excluded if they had patellofemoral dislocation or subluxation without a tibiofemoral dislocation. We retrospectively reviewed patient demographics, time to first dislocation, number of dislocations, time to surgical intervention, complications, and potential etiologies of tibiofemoral dislocation.Results: Twelve of 14 patients were female. Their mean body mass index was 33 ± 10 kg/m(2). Thirteen of 14 patients had a mean of 2.0 ± 1.4 dislocations. Four patients dislocated due to polyethylene damage and 5 due to ligamentous incompetence. Twelve of 14 patients required open surgical intervention. Complications in this patient population were common with 3 cases of infection, 7 cases of multiple dislocation, 2 cases of popliteal artery laceration, 1 case receiving a fusion, and 1 case receiving an amputation.Conclusion: Patients with tibiofemoral dislocation after TKA are predominantly obese, female, and have a high risk for complications. They dislocate predominantly because of polyethylene damage or ligamentous incompetence. Re-dislocation is common if treated with closed reduction alone. [ABSTRACT FROM AUTHOR]

Purpose. The current investigation aimed to examine the effects of running barefoot and in conventional and barefoot inspired footwear on the loads borne by the tibiofemoral joint. Methods. Fifteen male participants ran at 4.0 m/s over a force platform whilst running barefoot, in barefoot inspired footwear and also in conventional footwear. Lower body kinematics were collected using an eight-camera motion capture system. Peak tibiofemoral force, peak tibiofemoral stress, and tibiofemoral load rate were extracted and compared between footwear via one-way repeated measures ANOVA. Results. The results showed that the tibiofemoral instantaneous load rate was significantly lower in conventional footwear (106.63 BW/s) in comparison with barefoot running (173.87 BW/s), Vibram Five Fingers (160.17 BW/s), Merrell (155.32 BW/s), Inov-8 (167.79 BW/s), and Nike Free (144.72 BW/s). Conclusions. This indicates that running barefoot and in barefoot inspired footwear may place runners at increased risk from running-related tibiofemoral pathologies. [ABSTRACT FROM AUTHOR]

The aim of the current study was to comparatively examine the effects of minimalist and conventional footwear on the loads experienced by the tibiofemoral joint during running. Ten male participants ran at 4.0 m/s (±5%) over a force platform in minimalist and conventional footwear. Kinematics of the lower extremities were collected using an eight camera motion capture system. Peak tibiofemoral force, peak tibiofemoral stress and tibiofemoral force experienced per mile were extracted and compared between footwear using paired t-tests. The results showed that no differences (P>0.05) in peak force (conventional = 40.02±6.45 and minimalist = 38.68±7.79 N/kg), peak stress (conventional = 14.54±1.77 and minimalist = 13.98±2.52 MPa) or force experienced per mile (conventional = 3,358.35±584.83 and minimalist = 3,308.04±636.31 N/kg·mile) were evident between footwear. Therefore this indicates that minimalist footwear may not provide any further protection from running related tibiofemoral pathologies compared to conventional footwear. [ABSTRACT FROM AUTHOR]

Total knee arthroplasty (TKA) changes the knee joint in both intentional and unintentional, known and unknown, ways. Patellofemoral and tibiofemoral kinematics play an important role in postoperative pain, function, satisfaction and revision, yet are largely unknown. Preoperative kinematics, postoperative kinematics or changes in kinematics may help identify causes of poor clinical outcome. Patellofemoral kinematics are challenging to record since the patella is obscured by the metal femoral component in X-ray and moves under the skin. The purpose of this study was to determine the kinematic degrees of freedom having significant changes and to evaluate the variability in individual changes to allow future study of patients with poor clinical outcomes. We prospectively studied the 6 degrees of freedom patellofemoral and tibiofemoral weightbearing kinematics, tibiofemoral contact points and helical axes of rotation of nine subjects before and at least 1 year after total knee arthroplasty using clinically available computed tomography and radiographic imaging systems. Normal kinematics for healthy individuals were identified from the literature. Significant differences existed between pre-TKA and post-TKA kinematics, with the post-TKA kinematics being closer to normal. While on average the pre-total knee arthroplasty knees in this group displayed no pivoting (only translation), individually only five knees displayed this behaviour (of these, two showed lateral pivoting, one showed medial pivoting and one showed central pivoting). There was considerable variability postoperatively as well (five central, two lateral and two medial pivoting). Both preop and postop, flexion behaviour was more hinge-like medially and more rolling laterally. Helical axes were more consistent postop for this group. An inclusive understanding of the pre-TKA and post-TKA kinematics and changes in kinematics due to total knee arthroplasty could improve implant design, patient diagnosis and surgical technique. [ABSTRACT FROM AUTHOR]

Background and Aim: Researches had shown that the high levels of shear and compression stresses that appear in the articular cartilage after meniscectomy are partly responsible for cartilage pathologies, such as osteoarthrosis. In this study, we probe to determine the stress distribution of the medial and lateral meniscus and to choose the appropriate region of meniscectomy. Materials and Methods: Biomechanical 3D finite element model of the knee joint was generated from CT-scan images. Mimics modeled the bony structure of knee and Solidworks developed the medial and lateral meniscus. Results: Under an axial femoral compressive load, the maximal contact stress in the articular cartilage after meniscectomy was about twice that of a healthy joint. The maximal contact pressures took place in the posterior region of the medial meniscus, with average values of 1.622 MPa and in the anterior horn of the lateral menisci with 1.159 MPa. Results: Critical regions determine the allowed region of menisectomy for surgeon. Not only stress distribution doesn`t change by increasing of body weight or meniscectomy, but also the rate of stress increase after meniscectomy. [ABSTRACT FROM AUTHOR]

* STUDY DESIGN: Biomechanical cross-sectional study. * OBJECTIVE: To investigate the hypothesis that the cumulative load at the knee during running increases as running speed decreases. * BACKGROUND: The knee joint load per stride decreases as running speed decreases. However, by decreasing running speed, the number of strides per given distance is increased. Running a given distance at a slower speed may increase the cumulative load at the knee joint compared with running the same distance at a higher speed, hence increasing the risk of running-related injuries in the knee. * METHODS: Kinematic and ground reaction force data were collected from 16 recreational runners, during steady-state running with a rearfoot strike pattern at 3 different speeds (mean ± SD): 8.02 ± 0.17 km/h, 11.79 ± 0.21 km/h, and 15.78 ± 0.22 km/h. The cumulative load (cumulative impulse) over a 1000-m distance was calculated at the knee joint on the basis of a standard 3-D inverse-dynamics approach. * RESULTS: Based on a 1000-m running distance, the cumulative load at the knee was significantly higher at a slow running speed than at a high running speed (relative difference, 80%). The mean load per stride at the knee increased significantly across all biomechanical parameters, except impulse, following an increase in running speed. * CONCLUSION: Slow-speed running decreases knee joint loads per stride and increases the cumulative load at the knee joint for a given running distance compared to faster running. The primary reason for the increase in cumulative load at slower speeds is an increase in number of strides needed to cover the same distance. [ABSTRACT FROM AUTHOR]

Background: Altered local mechanical loading may disrupt normal cartilage homeostasis and play a role in the progression ofosteoarthritis. Currently, there are limited data quantifying local cartilage strains in response to dynamic activity in normal orinjured knees.Purpose/Hypothesis: To directly measure local tibiofemoral cartilage strains in response to a dynamic hopping activity in normalhealthy knees. We hypothesized that local regions of cartilage will exhibit significant compressive strains in response to hopping,while overall compartmental averages may not.Study Design: Controlled laboratory study.Methods: Both knees of 8 healthy subjects underwent magnetic resonance imaging before and immediately after a dynamic hoppingactivity. Images were segmented and then used to create 3-dimensional surface models of bone and cartilage. These preandpostactivity models were then registered using an iterative closest point technique to enable site-specific measurements ofcartilage strain (defined as the normalized change in cartilage thickness before and after activity) on the femur and tibia.Results: Significant strains were observed in both the medial and lateral tibial cartilage, with each compartment averaginga decrease of 5%. However, these strains varied with location within each compartment, reaching a maximum compressive strainof 8% on the medial plateau and 7% on the lateral plateau. No significant averaged compartmental strains were observed in themedial or lateral femoral cartilage. However, local regions of the medial and lateral femoral cartilage experienced significant compressivestrains, reaching maximums of 6% and 3%, respectively.Conclusion: Local regions of both the femur and tibia experienced significant cartilage strains as a result of dynamic activity. Anunderstanding of changes in cartilage strain distributions may help to elucidate the biomechanical factors contributing to cartilagedegeneration after joint injury.Clinical Relevance: Site-specific measurements of in vivo cartilage strains are important because altered loading is believed tobe a factor contributing to the development and progression of osteoarthritis. Specifically, this methodology and data could beused to evaluate the effects of soft tissue injuries (such as ligament or meniscus tears) on cartilage strains in response to dynamicactivities of daily living. [ABSTRACT FROM AUTHOR]

The standing lunge is an activity commonly used to quantify in-vivo knee kinematics with fluoroscopy. The ability to perform the standing lunge varies between subjects and can necessitate movement accommodations to successfully complete the desired range of motion. We proposed a supine leg press as an alternative to the standing lunge that aimed to provide a similar evaluation of knee motion while increasing the measured range of motion. Tibiofemoral kinematics of 53 non-symptomatic adults (27 men, 26 women, 50.8 ± 7.0 yrs.) were calculated from the tracked high-speed stereo radiography (HSSR) images for supine leg press and standing lunge using CT-segmented bony geometries of the right lower limb. The supine leg press proved to be a useful alternative to the standing lunge while providing 46.2° greater range of motion in knee flexion. The difference in angle-matched kinematics across a 100° flexion range between the leg press and lunge was 0.70° in varus-valgus rotation, 1.5° in internal-external rotation, 1.0 mm in medial–lateral translation, 2.3 mm in anterior-posterior translation, and 0.46 mm in superior-inferior translation for men. The angle-matched difference for women across 100° was 0.58° in varus-valgus rotation, 2.4° internal-external rotation, 0.70 mm medial–lateral translation, 2.1 mm anterior-posterior translation, and 0.78 mm superior-inferior translation. The similar kinematics, while having a greater range of motion, and control of the applied load makes the supine leg press an alternative for quantifying in-vivo knee kinematics. [ABSTRACT FROM AUTHOR]

A conservative management strategy for knee osteoarthritis is the lateral wedge insole (LWI). The theoretical basis for this intervention is to correct tibiofemoral malalignment, thereby reducing pain and optimising function. This systematic review evaluates the evidence on the effectiveness and safety of LWI for the treatment for knee osteoarthritis. A systematic review was performed, searching published (MEDLINE, AMED, EMBASE, CINAHL, Cochrane Library) and unpublished literature from their inception to August 2012. Randomised controlled trials (RCTs) were included that compared the use of LWI with a neutral insole or control intervention for people with medial compartment osteoarthritis. Risk of bias and clinical relevance were assessed, and outcomes were analysed through meta-analysis. From a total of 3,105 citations, 10 studies adhered to the a priori eligibility criteria. These included 1,095 people; 535 participants were allocated to receive LWI insoles compared to 509 in control groups. Eight per cent of papers were of high quality with low risk of bias. There was no statistically significant difference between LWI and neutral insoles for pain, function, analgesic requirement, compliance or complications ( p ≥ 0.07). Those who received LWI demonstrated lower non-steroidal anti-inflammatory drug requirements ( p < 0.001). To conclude, there is limited evidence to support the prescription of LWI to people with medial compartment osteoarthritis to reduce pain and increase function. However, there remains a paucity of evidence to determine whether LWI outcomes differ in subgroups of the patients, such as severe compared to mild osteoarthritis, obese patients, or whether the angle of LWI is of clinical importance. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate in vivo threedimensional tibiofemoral kinematics and femoral condylar motion in knees with anterior cruciate ligament (ACL) deficiency during a knee bend activity. Ten patients with unilateral ACL rupture were enrolled. Both the injured and contralateral normal knees were imaged using biplane radiography at extension and at 15°, 30°, 60°, 90°, and 120° of flexion. Bilateral knees were next scanned by computed tomography, from which bilateral three-dimensional knee models were created. The in vivo tibiofemoral motion at each flexion position was reproduced through image registration using the knee models and biplane radiographs. A joint coordinate system containing the geometric center axis of the femur was used to measure the tibiofemoral motion. In ACL deficiency, the lateral femoral condyle was located significantly more posteriorly at extension and at 15° (p < 0.05), whereas the medial condylar position was changed only slightly. This constituted greater posterior translation and external rotation of the femur relative to the tibia at extension and at 15° (p < 0.05). Furthermore, ACL deficiency led to a significantly reduced extent of posterior movement of the lateral condyle during flexion from 15° to 60° (p < 0.05). Coupled with an insignificant change in the motion of the medial condyle, the femur moved less posteriorly with reduced extent of external rotation during flexion from 15° to 60° in ACL deficiency (p < 0.05). The medial-lateral and proximaldistal translations of the medial and lateral condyles and the femoral adduction-abduction rotation were insignificantly changed after ACL deficiency. The results demonstrated that ACL deficiency primarily changed the anterior-posterior motion of the lateral condyle, producing not only posterior subluxation at low flexion positions but also reduced extent of posterior movement during flexion from 15° to 60°. [ABSTRACT FROM AUTHOR]

The article discusses a study which was aimed to compare the net peak external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. The study was conducted on 16 recreationally trained men with no previous lower-limb surgeries or other orthopedic issues and at least 1 year of consistent resistance training experience. The study findings suggest that typical decreases in squat loads used with increasing depths are not enough to offset increases in pEKFM.

Background: The assessment of joint position sense (JPS) is the most widely used measurement of knee proprioceptive capability within the literature. However, it remains unclear what the most reliable method is to assess this. The purpose of this study was to determine the intra- and inter-rater reliability of the various methods used to assess knee JPS. Methods: A systematic review of published and unpublished literature sources was conducted up to June 2012. All studies principally assessing the reliability (intra- or inter-rater) or reproducibility of a JPS of the knee were included. The methodological quality of each study was reviewed using the Critical Appraisal Skills Programme tool. Results: A total of 18 studies were eligible, assessing the reliability of JPS with 456 knees. The reliability of four methods of JPS has been recorded: position replication using a model, image recorded angulation, electrogoniometry and dynamometry/angular motion chair. Intra-rater reliability was good for the assessment of JPS using photographs and digital images, and replicating knee position using a paper model, this was good but variable when electrogoniometry was used, and moderate but variable when assessed using dynamometry/angle motion chairs. The assessment of JPS by image recorded angulation, electrogoniometry and dynamometry/angular motion chair has demonstrated good inter-rater reliability. Conclusions: Whilst JPS methods appear to have variable reliability, the four assessment methods should be further assessed with pathological populations such as those following patellar dislocation or anterior cruciate ligament rupture. This will better facilitate the generalisability of JPS assessment methods to inform clinical practice. [ABSTRACT FROM AUTHOR]

The article presents a cohort study that assessed the association of patient, functional, and clinical outcomes and type II collagen metabolism with abnormal tibiofemoral joint space width (JSW). It included patients suffering from anterior cruciate ligament (ACL) disruptions. Evidence showed that ACL injured patients with an abnormal tibiofemoral JSW were discovered with diminished quality of life, increased pain, and increased type II collagen.

Osteoarthritis (OA) is a leading cause of functional impairment and pain. Proprioceptive defects may be associated with the onset and progression of OA of the knee. The purpose of this study was to determine the effectiveness of proprioceptive exercises for knee OA using meta-analysis. A systematic review was conducted on 12th December 2011 using published (Cochrane Library, MEDLINE, EMBASE, CINAHL, AMED, PubMed, PEDro) and unpublished/trial registry (OpenGrey, the WHO International Clinical Trials Registry Platform, Current Controlled Trials and the UK National Research Register Archive) databases. Studies were included if they were full publications of randomized or non-randomised controlled trials (RCT) comparing a proprioceptive exercise regime, against a non-proprioceptive exercise programme or non-treatment control for adults with knee OA. Methodological appraisal was performed using the PEDro checklist. Seven RCTs including 560 participants (203 males and 357 females) with a mean age of 63 years were eligible. The methodological quality of the evidence base was moderate. Compared to a non-treatment control, proprioceptive exercises significantly improved functional outcomes in people with knee OA during the first 8 weeks following commencement of their exercises ( p < 0.02). When compared against a general non-proprioceptive exercise programme, proprioceptive exercises demonstrated similar outcomes, only providing superior results with respect to joint position sense-related measurements such as timed walk over uneven ground ( p = 0.03) and joint position angulation error ( p < 0.01). Proprioceptive exercises are efficacious in the treatment of knee OA. There is some evidence to indicate the effectiveness of proprioceptive exercises compared to general strengthening exercises in functional outcomes. [ABSTRACT FROM AUTHOR]

The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case-control study was performed in subjects without radiographic knee osteoarthritis (OA) (K&L grade <2) matched on sex, BMI, age, knee compartment, and meniscectomy where cases ( n = 28) had cartilage defects (grade ≥2) and controls ( n = 28) had no cartilage defects (grade <2). Cartilage defects were assessed from MRI using validated methods. The VOT was applied to TB regions selected on medial and lateral compartments in knee X-rays and fractal signatures (FS) in the horizontal (FS) and vertical (FS) directions, and along the roughest part of TB (FS) and texture aspect ratio signatures (StrS), at different trabecular image sizes (0.30-0.70 mm) were calculated. Compared with controls, FS for cases were higher ( p < 0.011) at image sizes 0.30-0.40 mm and 0.45-0.55 mm in the medial compartment. In the lateral compartment, FS and FS for cases were higher ( p < 0.028) than those for controls at 0.30-0.40 mm and 0.45-0.55 mm, while FS was higher ( p < 0.02) at 0.30-0.40 mm. TB texture roughness was greater in subjects with cartilage defects than in subjects without, suggesting thinning and fenestration of TB occur early in OA and that the VOT identifies changes in TB in knees with early cartilage damage. No differences in StrS ( p > 0.05) were found. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1161-1167, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Determining the 3D pose of the patella after total knee arthroplasty is challenging. The commonly used single-plane fluoroscopy is prone to large errors in the clinically relevant mediolateral direction. A conventional fixed bi-planar setup is limited in the minimum angular distance between the imaging planes necessary for visualizing the patellar component, and requires a highly flexible setup to adjust for the subject-specific geometries. As an alternative solution, this study investigated the use of a novel multi-planar imaging setup that consists of a C-arm tracked by an external optoelectric tracking system, to acquire calibrated radiographs from multiple orientations. To determine the accuracies, a knee prosthesis was implanted on artificial bones and imaged in simulated ‘Supine’ and ‘Weightbearing’ configurations. The results were compared with measures from a coordinate measuring machine as the ground-truth reference. The weightbearing configuration was the preferred imaging direction with RMS errors of 0.48mm and 1.32° for mediolateral shift and tilt of the patella, respectively, the two most clinically relevant measures. The ‘imaging accuracies’ of the system, defined as the accuracies in 3D reconstruction of a cylindrical ball bearing phantom (so as to avoid the influence of the shape and orientation of the imaging object), showed an order of magnitude (11.5 times) reduction in the out-of-plane RMS errors in comparison to single-plane fluoroscopy. With this new method, complete 3D pose of the patellofemoral and tibiofemoral joints during quasi-static activities can be determined with a many-fold (up to 8 times) (3.4mm) improvement in the out-of-plane accuracies compared to a conventional single-plane fluoroscopy setup. [Copyright &y& Elsevier]

The usefulness of forward dynamic simulations to studies of human motion is well known. Although the musculoskeletal models used in these studies are generic, the modeling of specific components, such as the knee joint, may vary. Our two objectives were (1) to investigate the effects of three commonly used knee models on forward dynamic simulation results, and (2) to study the sensitivity of simulation results to variations in kinematics for the most commonly used knee model. To satisfy the first objective, three different tibiofemoral models were incorporated into an existing forward dynamic simulation of recumbent pedaling, and the resulting kinematics, pedal forces, muscle forces, and joint reaction forces were compared. Two of these models replicated the rolling and sliding motion of the tibia on the femur while the third was a simple pin joint. To satisfy the second objective, variations in the most widely used of the three knee models were created by adjusting the experimental data used in the development of this model. These variations were incorporated into the pedaling simulation, and the resulting data were compared with the unaltered model. Differences between the two rolling-sliding models were smaller than differences between the pin-joint model and the rolling-sliding models. Joint reactions forces, particularly at the knee, were highly sensitive to changes in knee joint model kinematics, as high as 61% root mean squared difference, normalized by the corresponding peak force of the unaltered reference model. Muscle forces were also sensitive, as high as 30% root mean squared difference. Muscle excitations were less sensitive. The observed changes in muscle force and joint reaction forces were caused primarily by changes in the moment arms and musculotendon lengths of the quadriceps. Although some level of inaccuracy in the knee model may be acceptable for calculations of muscle excitation timing, a representative model of knee kinematics is necessary for accurate calculation of muscle and joint reaction forces. [ABSTRACT FROM AUTHOR]

The article presents a study to determine the interrater reliability of a 5-point grading scale in evaluating knee joint effusion. Subjects included 75 orthopaedic physical therapy outpatients for treatment of a unilateral knee dysfunction. Knee joint effusion is evaluated through a stroke test and quantified using a clinical scale where a visual observation of fluid mechanics is performed. Results of the study show that the clinical grading scale is a reliable method to monitor exercise progression and functional testing.

Purpose: The purpose of this study was to compare the tibiofemoral contact area and pressure after single-bundle (SB) and double-bundle (DB) anterior cruciate ligament (ACL) reconstruction by use of 2 femoral and 2 tibial tunnels in intact cadaveric knees. Methods: Tibiofemoral contact area and mean and maximum pressures were measured by pressure-sensitive film (Fujifilm, Valhalla, NY) inserted between the tibia and femur. The knee was subjected to a 1,000-N axial load by use of a uniaxial testing machine at 0°, 15°, 30°, and 45° of flexion. Three conditions were evaluated: (1) intact ACL, (2) SB ACL reconstruction (n = 10 knees), and (3) DB ACL reconstruction (n = 9 knees). Results: When compared with the intact knee, DB ACL reconstruction showed no significant difference in tibiofemoral contact area and mean and maximum pressures. SB ACL reconstruction had a significantly smaller contact area on the lateral and medial tibiofemoral joints at 30° and 15° of flexion. SB ACL reconstruction also had significantly higher mean pressures at 15° of flexion on the medial tibiofemoral joint and at 0° and 15° of flexion on the lateral tibiofemoral joint, as well as significantly higher maximum pressures at 15° of flexion on the lateral tibiofemoral joint. Conclusions: SB ACL reconstruction resulted in a significantly smaller tibiofemoral contact area and higher pressures. DB ACL more closely restores the normal contact area and pressure mainly at low flexion angles. Clinical Relevance: Our findings suggest that the changes in the contact area and pressures after SB ACL reconstruction may be one of the causes of osteoarthritis on long-term follow-up. DB ACL reconstruction may reduce the incidence of osteoarthritis by closely restoring contact area and pressure. [Copyright &y& Elsevier]

Abstract: We developed an analytical biomechanical model for leg-extension equipment and the associated knee-extension/flexion exercises. The shear component, ϕ t , of the tibiofemoral joint load was calculated taking into account all the fundamental elements of the equipment mechanics (resistance pad placement, cam/pulley system geometry, selected weight stack, etc.) and the instantaneous values of the relevant kinematical parameters (knee-flexion angle (θ f), angular velocity, and angular acceleration). The optimal distance (a R )OPT between the knee-flexion/extension axis and the resistance pad placement point was derived by minimizing ϕ t . (a R )OPT is nearly independent of joint angular velocity and, for appreciably high resistance torques, becomes nearly independent of resistance level and cam/pulley geometry: for θ f >40°, ϕ t is minimized by placing the resistance pad distally along the lower leg; for θ f ≤40°, ϕ t can be completely eliminated by continuously moving the resistance pad proximally during knee-extension phase and distally during knee-flexion phase (0.17m≤(a R )OPT ≤0.4m). In the presence of knee angular accelerations and hamstrings co-contractions, not predictable in advance, the value of (a R )OPT obtained neglecting these effects still represents a good compromise for joint protection. This work establishes the rational basis for the design and clinical use of a leg-extension equipment that minimizes ϕ t . [Copyright &y& Elsevier]

Abstract: Background: Lateral shoe wedges and valgus knee braces are designed to decrease the force acting in the medial knee compartment by reducing the external adduction moment applied at the knee. The biomechanical changes introduced by these orthoses can be relatively small. Computer modeling and simulation offers an alternative approach for assessing the biomechanical performance of these devices. Methods: A three-dimensional model of the lower-limb was used to calculate muscle, ligament, and joint loading at the knee during gait. A lateral shoe wedge was simulated by moving the center of pressure of the ground reaction force up to 5mm laterally. A valgus knee brace was simulated by applying abduction moments of up to 12Nm at the knee. Findings: Knee adduction moment and medial compartment load decreased linearly with lateral displacement of the center of pressure of the ground reaction force. A 1 mm displacement of the center of pressure decreased the peak knee adduction moment by 2%, while the peak medial compartment load was reduced by 1%. Knee adduction moment and medial compartment force also decreased linearly with valgus moments applied about the knee. A 1Nm increase in brace moment decreased the peak knee adduction moment by 3%, while the peak medial compartment load was reduced by 1%. Interpretation: Changes in knee joint loading due to lateral shoe wedges and valgus bracing are small and may be difficult to measure by conventional gait analysis methods. The relationships between lateral shift in the center of pressure of the ground force, valgus brace moment, knee adduction moment, and medial joint load can be quantified and explained using computer modeling and simulation. These relationships may serve as a useful guide for evaluating the biomechanical efficacy of a generic wedge insole or knee brace. [Copyright &y& Elsevier]

The purpose of this study was to evaluate tibiofemoral kinematics after double-bundle anterior cruciate ligament (ACL) reconstructions and compare them with those of successful single-bundle reconstructions and contralateral normal knees using open MR images. We obtained MR images based on the flexion angle without weight-bearing, from 20 patients with successful unilateral single-bundle (10 patients) and double-bundle (10 patients) ACL reconstructions with tibialis anterior allografts and a minimum 1-year follow-up. The MR images of the contralateral uninjured knees were used as normal controls. Sagittal images of the mid-medial and mid-lateral sections of the tibiofemoral compartments were used to measure the translation of the femoral condyles relative to the tibia. The mean translations of the medial femoral condyles on the tibial plateaus during knee joint motion showed no significant differences among normal, single-bundle, and double-bundle ACL reconstructed knees (all p>0.05). The mean translations of the lateral femoral condyles showed a significant difference between normal and single-bundle reconstructed knees, or between single-bundle and double-bundle reconstructed knees (p<0.05). However, there was no significant difference between normal and double-bundle reconstructed knees (p=0.220). These findings suggest that double-bundle ACL reconstruction restores normal kinematic tibiofemoral motion better than single-bundle reconstruction. [ABSTRACT FROM AUTHOR]

Abstract: The patellar tendon moment arm is a critical quantity in that it defines the quadriceps ability to generate a moment on the tibia. Thus, the primary purpose of this study was to establish the first in vivo three-dimensional measures of the patellar tendon moment arm, measured non-invasively and in vivo during dynamic activity in a large normative population (n=34) using a dynamic MRI technique (fast-PC MRI). The magnitude of the moment arm was defined as the shortest distance between the finite helical axis and the patellar tendon line of action. Using these data, the hypothesis that the patellar tendon moment arm is independent of gender was tested. In general, the moment arm increased from 20 to 50mm during knee extension. There were significant differences (P<0.05) in the moment arm between gender, but these differences were eliminated when the moment arm was scaled by the femoral epicondylar width. This study took a large step forward towards the ultimate goal of defining how pathology may alter joint dynamics through alteration in moment arms by establishing the first in vivo normative data base for the patellar tendon moment arm using non-invasive measures during volitional activity in a relatively large population (n=34). The fact that the scaled moment arm was independent of gender may lend insights into impairments that tend to be gender specific, such as patellar maltracking. The next steps will be to quantify the patellar tendon moment arm in populations with specific pathologies. [Copyright &y& Elsevier]

In order to advance biomechanical modeling, knee joint implant design and clinical treatment of knee joint pathology, accurate in vivo kinematic data of the combined patellofemoral and tibiofemoral joint during volitional activity are critical. For example, one cause of the increased prevalence of anterior knee pain in the female population is hypothesized to be altered tibiofemoral kinematics, resulting in pathological patellofemoral kinematics. Thus, the objectives of this paper were to test the hypothesis that knee joint kinematics vary based on gender and to explore the correlation between the 3-D kinematics of the patellofemoral and tibiofemoral joints. In order to accomplish these goals, a large (n = 34) normative database of combined six degree of freedom patellofemoral and tibiofemoral kinematics, acquired noninvasively during volitional knee extension-flexion using fast-PC (dynamic) magnetic resonance imaging, was established. In this normative database, few correlations between tibiofemoral and patellofemoral kinematics were found. Specifically, tibial external rotation did not predict lateral patellar tilt, as has been stated in previous studies. In general, significant differences could not be found based on gender. Further investigation into these relationships in the presence of pathology is warranted. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis (OA) is characterized by joint changes, such as cartilage degradation, subchondral sclerosis and osteophyte formation around the margin of the articular surface. The knee joint has three compartments: the medial tibiofemoral, the lateral tibiofemoral and the patellofemoral. Although most epidemiological studies have predominantly examined risk factors for tibiofemoral rather than patellofemoral disease, pain associated with knee OA commonly emanates from the patellofemoral joint. Evaluating the patellofemoral joint using radiography is problematic, which may have led to the paucity of data on patellofemoral OA. However, the advent of magnetic resonance imaging has enabled direct visualization of the entire knee joint and has given new insights into the pathogenesis of joint pathologies, such as OA. This discussion aims to compare and contrast patellofemoral and tibiofemoral OA and, thus, highlight that they are independent entities and, as such, must be examined as separate pathological processes. Moreover, this discussion demonstrates how new imaging modalities are providing insight into the pathogenesis of patellofemoral OA. [ABSTRACT FROM AUTHOR]

Autologous chondrocyte implantation is an advanced, cell-based orthobiological technology used for the treatment of chondral defects of the knee. It has been in clinical use since 1987 and has been performed on 12 000 patients internationally; but despite having been in clinical use for more than 15 years, the evidence base for rehabilitation after autologous chondrocyte implantation is notably deficient. The authors review current clinical practice and present an overview of the principles behind autologous chondrocyte implantation rehabilitation practices. They examine the main rehabilitation components and discuss their practical applications within the overall treatment program, with the aim of facilitating the formulation of appropriate, individualized patient rehabilitation protocols for autologous chondrocyte implantation. [ABSTRACT FROM AUTHOR]

Purpose: In vivo measurement of the forces and strains in human tissues is currently impracticable. Computer modeling and simulation allows estimates of these quantities to be obtained noninvasively. This paper reviews our recent work on muscle, ligament, and joint loading at the knee during gait. Methods: Muscle and ground-reaction forces obtained from a sophisticated computer simulation of walking were input into a detailed model of the lower limb to obtain ligament and joint-contact loading at the knee for one full cycle of gait. Results: Peak anterior cruciate ligament (ACL) force occurred in early stance and was mainly determined by the anterior pull of the patellar tendon on the tibia. The medial collateral ligament was the primary restraint to anterior tibial translation (ATT) in the ACL-deficient knee. All in the ACL-deficient knee can be reduced to the level calculated for the intact knee by increasing hamstrings muscle force. Reducing quadriceps force was insufficient to restore ATT to the level calculated for the intact knee. For both normal and ACL-deficient walking, the resultant force acting between the femur and tibia remained mainly on the medial side of the knee. The knee adductor moment was resisted by a combination of muscle and ligament forces. Conclusion: Knee-ligament loading during the stance phase of gait is explained by the pattern of anterior shear force applied to the leg. The distribution of force at the tibiofemoral joint is determined by the variation in the external adductor moment applied at the knee. The forces acting at the tibiofemoral and patellofemoral joints are similar during normal and ACL-deficient gait. Hamstrings facilitation is more effective than quadriceps avoidance in reducing AU during ACL-deficient gait. [ABSTRACT FROM AUTHOR]

Abstract: The contact stresses in the knee that arise from activities involving deep flexion have not been given due consideration in view of social and cultural practice amongst many Asians that frequently cause the engagement of these activities. Excessively large stresses (>25MPa) can cause cartilage damage and may be the precursor to the development of degenerative disease of the joint. In this study, forces in the knee derived from previous studies of human walking and squatting were applied to five cadaver knees that underwent quasi-static mechanical testing. This was conducted using a materials-testing machine and a custom-made apparatus that allowed secure and consistent loading of the knee specimen in flexion beyond 120°. A thin-film electronic pressure transducer was inserted into the cadaver tibiofemoral joint space to measure force and area. Throughout the various positions simulating specific phases of walking, it was found that stresses peaked to 14MPa (standard deviation was 2.5MPa). In deep flexion, the peak stresses were significantly larger by over 80%, reaching the damage limits of cartilage. The results from this biomechanical study suggest that the adequacy of articular cartilage to support loads in the knee joint during deep flexion may be questionable. [Copyright &y& Elsevier]

Squats are frequently performed to strengthen the quadriceps (Quad) and gluteus maximus (GM) in sports and clinical fields. Since the squat itself produces a large knee contact force, clarifying the relationship between the squat techniques and the knee contact force is important. However, the influence of different squat techniques on the medial knee contact force (KCFmed), which would result in knee disease, remains unclear. This study aimed to investigate the influence of various squat techniques on KCFmed during bodyweight squats. Since muscle strengthening by the squat is inevitable, we additionally aimed to explore the effect of a different squat technique on the quadriceps (Quad) and gluteus maximus (GM) forces. Twelve healthy adults performed squats with different stance widths (narrow stance, NS; middle stance, MS; and wide stance, WS) and different toe directions (0° of forefoot abduction – NEUT and 30°forefoot abduction – OUT). The KCFmed, Quad force, and GM force were computed using a musculoskeletal model with marker trajectories and ground reaction forces. The KCFmed in NS was significantly larger than that in MS and WS, and KCFmed in OUT was significantly larger than that in NEUT. The Quad force in OUT was significantly larger than that in the NEUT, and the GM force significantly became larger as the stance width became narrower. These findings suggest that squats in MS and NEUT may be suitable for reducing KCFmed while maintaining the Quad and GM forces. [ABSTRACT FROM AUTHOR]