Search

Kinematic differences between patients with osteoarthritis (OA) and control participants have been reported to be influenced by gait speed. The purpose of this study was to experimentally detect the effect of walking speed on differences in spatiotemporal parameters and kinematic trajectories between patients with hip OA and age-matched asymptomatic participants using wearable sensors and statistical parametric mapping (SPM). Twenty-four patients with severe unilateral hip OA and 48 control participants were included in this study. Patients walked at a self-selected normal speed and control participants at self-selected normal and slow speeds. Spatiotemporal parameters and kinematic trajectories were measured with the inertial sensor system Rehagait®. Gait parameters were compared between patients with hip OA and control participants for normal and matched speed using SPM with independent sample t-tests. At self-selected normal speed, the patient group walked slower (-0.20 m/s, p

Background The aims of this study were to assess and quantify hip abductor muscle strength deficits after total hip arthroplasty (THA) and to determine associations with external factors. Methods Studies reporting on hip abductor muscle strength before and/or after THA performed for osteoarthritis or atraumatic osteonecrosis of the hip were considered for inclusion. Data sources were Embase, Medline, and the Cochrane Central Register of Controlled Trials. Muscle strength on the affected side was compared with the healthy contralateral side or with control subjects. Study quality was assessed using a modified Newcastle-Ottawa Scale. Results Nineteen studies reporting on 875 subjects met the inclusion criteria. Patients scheduled for THA had a mean strength deficit of 18.6% (95% confidence interval (CI) [−33.9, −3.2%]) compared with control subjects. Abductor muscle strength then increased by 20.2% (CI [5.6, 34.8%]) at 4-6 months, 29.6% (CI [4.7, 54.4%]) at 9-12 months, and 49.8% (CI [−31.0, 130.6%]) at 18-24 months postoperatively compared with preoperative values. For unilateral THA, the mean torque ratio was 86.3% (CI [75.4, 97.2%]) and 93.4% (CI [75.1, 111.6%]) before and >24 months after THA, respectively. Study quality was low to moderate. Conclusion Hip abductor muscle strength deficits may gradually improve during 24 months after THA possibly without complete recovery. Cautious interpretation of these findings is warranted because high-quality evidence is largely missing.

Background Kinematic changes in patients with knee osteoarthritis (OA) have been extensively studied. Concerns have been raised whether the measured spatiotemporal and kinematic alterations are associated with disease progression or merely a result of reduced walking speed. Research question: The purpose of this study was to investigate the effect of walking speed on kinematic parameters in patients with knee OA using statistical parametric mapping (SPM). Methods Twenty-three patients with unilateral knee OA scheduled for a total knee replacement and 28 age matched control subjects were included in this study. Spatiotemporal parameters and sagittal plane kinematics were measured in the hip, knee, and ankle using the inertial sensors system RehaGait® while walking at a self-selected normal (patients and controls) and slow walking speed (controls) for a distance of 20 m. Gait parameters were compared between groups for self-selected walking speed and for matched walking speed using SPM with independent sample t tests. Results At self-selected walking speed, patients had significantly lower knee flexion during stance (maximum difference, -6.8°) and during swing (-11.0°), as well as higher ankle dorsiflexion during stance phase (+12.5°) and lower peak hip extension at the end of stance compared to controls (+4.2°). At matched speed, there were no significant differences in joint kinematics between groups. Significance Differences in sagittal plane gait kinematics between patients with knee OA and asymptomatic controls appear to be mainly a result of reduced walking speed. These results emphasize the importance of considering walking speed in research on gait kinematics in patients with knee OA and in clinical trials using gait parameters as outcome measures.

Summary Objective The aim of this study was to document the natural history of development and long-term progression of osteoarthritis (OA) in the feline knee after minimally invasive anterior cruciate ligament (ACL) transection. Design ACL transections of the left knee joint of 14 skeletally mature cats were performed. Radiographic scores, tibiofemoral and patellofemoral joint space and anterior tibial translation were assessed before, immediately and every 3 months after ACL transection (longest follow-up: 93 months). Results After 26 months, all ACL transected knees had developed definite OA. The earliest changes were observed on the tibia plateau starting as early as 2 months after ACL transection, and at 12 months signs of OA were present in more than 80% of cats in the medial and in almost 80% of cats in the lateral compartment. In the first 24 months, medial tibiofemoral joint space decreased by 0.88 mm (95% confidence interval [−0.55;−1.21] mm) and lateral tibiofemoral joint space by 0.55 mm ([−0.26;−0.85] mm). In the same interval, the joint space in the patellofemoral joint increased by 0.98 mm ([0.59; 1.37] mm). Throughout the entire observation period, the anterior tibial translation was on average 5.3 mm greater than in the contralateral knee ([4.5; 6.0]mm). Conclusions Immediate changes in anterior tibial translation during an anterior drawer test clearly showed joint instability that persisted throughout the lifetime of the animals. Degenerative changes were observed on radiographs within 4 months of the injury only in the transected but not the contralateral limb suggesting the role of mechanical instability for the development and progression of knee OA.

The purpose of this study was to quantify changes in volumetric bone mineral density (vBMD) in the tibial plateau of the operated and contralateral leg measured using peripheral quantitative computed tomography (pQCT) before and 3, 6, and 12 months after anterior cruciate ligament (ACL) reconstruction. The ACL was reconstructed with a hamstring tendon autograft using press-fit fixation. pQCT measurements of the proximal tibia were obtained in 61 patients after ACL reconstruction, and total, cortical, and trabecular vBMD were calculated. vBMD in the operated leg decreased from baseline to 3 months (-12% [total], -11% [cortical], and -12.6% [trabecular]; p

The use of forearm crutches has been associated with pain and neuropraxia along the ulnar bone. Whilst anatomic grips have improved comfort of crutch walking, to date anatomic forearm cuffs have not been clinically evaluated. The aim of this clinical pilot study was to determine if the use of forearm crutches with anatomic cuffs reduces pain and increases comfort and function in long-term users of forearm crutches during a 4-week period. Prospective study in ten patients suffering from end-stage osteoarthritis of the lower extremity. All participants were long-term users of conventional forearm crutches. Participants used forearm crutches with an anatomically shaped cuff for 4-weeks. General health was assessed using the SF-36, and the crutches were evaluated using a newly developed questionnaire focusing on symptoms along the forearm. Pain and paresthesia along the forearms decreased by 3.3 points (95% confidence interval difference (CI): [−5.0; −1.6], p = .004) and 3.5 points (95%CI: [−5.1; −1.9], p = .002), respectively, after using the crutches with the new anatomic cuff for 4 weeks. Comfort and sense of security of crutch use increased by 3.0 points (95%CI: [1.3; 4.7], p = .007) and 2.4 points (95%CI: [0.7; 4.1], p = .024). Cross-correlation analysis revealed correlations among items in the same item category and no correlations between items of different item categories of the new questionnaires. An anatomically shaped cuff increases comfort of forearm crutches. Further research should confirm long-term clinical improvement. This study was registered retrospectively in ISRCTN (TRN: ISRCTN 11135150 ) on 14/02/2017.

The aim of this study was to test the hypothesis that hip muscle function (strength and endurance) improves after total hip arthroplasty and is important for minimizing limping gait.Fifty-two patients who underwent total hip arthroplasty were assessed before and 6 mos after receiving a unilateral total hip endoprosthesis (Adaptiva stem with a Harris-Galante acetabular component). Severity of limping was assessed using a 4-point ordinal scale. Pain was assessed using a standardized ordinal scale. Eccentric, concentric, and isometric muscle strength and endurance of the hip extensors, flexors, adductors, and abductors were measured using a dynamometer.Postoperative limping severity and pain were significantly lower and postoperative muscle strength and endurance were significantly higher than the preoperative values (P0.05). The association between impaired muscle strength and endurance and limping severity was stronger postoperatively than preoperatively. This association was stronger for the hip extensor and flexor muscles than for the hip adductor and abductor muscles. Pain level was not associated with postoperative limping severity.Hip extensor and flexor muscle strength and endurance seem to be relevant for minimizing postoperative limping in patients after total hip arthroplasty. Rehabilitation programs should include exercises aimed at improving hip extensor and flexor strength and endurance to improve gait function.

Context Footwear modifications have been investigated as conservative interventions to decrease peak external knee adduction moment (EKAM) and pain associated with knee osteoarthritis (OA). Objective To evaluate the literature on the effect of different footwear and orthotics on the peak EKAM during walking and/or running. Methods A systematic search of databases resulted in 348 articles of which 33 studies were included. Results Seventeen studies included healthy individuals and 19 studies included subjects with medial knee OA. Quality assessment (modified Downs and Black quality index) showed an (average±SD) of 73.1±10.1%. The most commonly used orthotic was the lateral wedge, with three studies on the medial wedge. Lateral wedging was associated with decreased peak EKAM in healthy participants and participants with medial knee OA while there is evidence for increased peak EKAM with the use of medial wedges. Modern footwear (subjects' own shoe, "stability" and "mobility" shoes, clogs) were likely to increase the EKAM compared to barefoot walking in individuals with medial knee OA. Walking in innovative shoes ("variable stiffness") decreased the EKAM compared to control shoes. Similarly, shoes with higher heels, sneakers and dress shoes increased EKAM in healthy individuals compared to barefoot walking. Conclusions Further development may be needed toward optimal footwear for patients with medial knee OA with the aim of obtaining similar knee moments to barefoot walking.

This study tested the effects of variable-stiffness shoes on knee adduction moment, pain, and function in subjects with symptoms of medial compartment knee osteoarthritis over 6 months. Patients were randomly and blindly assigned to a variable-stiffness intervention or constant-stiffness control shoe. The Western Ontario and McMaster Universities (WOMAC) score served as the primary outcome measure. Joint loading, the secondary outcome measure, was assessed using the external knee adduction moment. Peak external knee adduction moment, total WOMAC, and WOMAC pain scores were assessed at baseline and after 6 months. The total WOMAC and WOMAC pain scores for the intervention group were reduced from baseline to 6 months (p = 0.017 and p = 0.002, respectively), with no significant reductions for the control group. There was no difference between groups in magnitude of the reduction in total WOMAC (p = 0.50) or WOMAC pain scores (p = 0.31). The proportion of patients achieving a clinically important improvement in pain was greater in the intervention group than in the control group (p = 0.012). The variable-stiffness shoes reduced the peak knee adduction moment (-6.6% vs. control, p < 0.001) in the 34 intervention subjects at 6 months. The adduction moment reduction significantly improved (p = 0.03) from the baseline reduction. The constant-stiffness control shoe increased the peak knee adduction moment (+6.3% vs. personal, p = 0.004) in the 26 control subjects at 6 months. The results of this study showed that wearing the variable-stiffness shoe lowered the adduction moment, reduced pain, and improved functionality after 6 months of wear. The lower adduction moment associated with wearing this shoe may slow the rate of progression of osteoarthritis after long-term use.

The aim of this study was to test the hypothesis that a change in serum cartilage oligomeric matrix protein (COMP) concentration is related to joint load during a 30-min walking exercise in patients with medial compartment knee osteoarthritis (OA) and in age-matched control subjects. Blood samples were drawn from 42 patients with medial compartment knee OA and from 41 healthy age-matched control subjects immediately before, immediately after, and 0.5, 1.5, 3.5, and 5.5 h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. Serum COMP concentrations were determined using a commercial ELISA. Basic time-distance gait variables were recorded using an activity monitor. Joint loads were measured using gait analysis. Serum COMP concentrations increased immediately after the walking exercise (+6.3% and +5.6%; p < 0.001) and decreased over 5.5 h after the exercise (-11.1% and -14.6%; p < 0.040 and p = 0.001) in patients and control subjects, respectively. The magnitude of increase in COMP concentration did not differ between groups (p = 0.902) and did not correlate with any variables describing ambulatory loads at the joints of the lower extremity. These results, taken together with a previous study of a younger healthy population, suggest the possibility that the influence of ambulatory loads on cartilage turnover is dependent on age.

The mechanical axis alignment of the lower extremity is typically measured from frontal plane radiographs of the entire lower extremity during double support standing. The purpose of this study was to test the hypothesis that the mechanical axis alignment can be predicted from skin markers on anatomical landmarks and anthropometric measurements and a stereophotogrammetric system based on significant correlation with the mechanical axis alignment measured from standing radiographs. Mechanical axis alignment was measured using full-limb radiographs for both knees of 62 patients with bilateral medial compartment knee osteoarthritis (OA). Mechanical axis alignment was also measured using a stereophotogrammetric system with markers on anatomical landmarks and anthropometric measurements to determine joint centers. The mechanical axis alignment from position capture correlated with that from radiographs (R(2)=0.544; P

The purpose of this study was to determine if there is a distinctive characteristic in the pattern of movement (forward trunk lean to reduce demand on the quadriceps muscle) during stair climbing in patients with knee osteoarthritis (OA) that is associated with the severity of the disease. Twenty-three patients with radiographically diagnosed knee OA and 20 physically active adults performed stair ascending trials without support at their self-selected speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Forward trunk lean, or trunk flexion, was defined as the sagittal plane projection of the angle between a line connecting the midpoint of the trans-acromion line and the midpoint of the trans-iliac crest line and the global vertical axis. Patients with more severe knee OA (KL ≥ 3) had greater forward trunk lean (+6.3°, p = 0.045) and lower knee net quadriceps moments (−35.2%, p = 0.001) than controls. In more severe patients, the forward trunk lean was correlated with a reduction in the net quadriceps moment during stair climbing (R2 = 0.590, p = 0.006). The results of this study identified a distinctive compensatory pattern of movement to reduce the quadriceps demand during stair climbing in patients with more severe knee OA by increasing forward trunk lean. Assessing forward trunk lean during stair climbing may be a useful functional marker for evaluating osteoarthritis status and quadriceps function that appears to be a more sensitive indicator of disease severity than perceived pain. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:325–329, 2009

Objective This study tested the hypothesis that gait changes related to knee osteoarthritis (OA) of varied severity are associated with increased loads at the ankle, knee, and hip. Methods Forty-two patients with bilateral medial compartment knee OA and 42 control subjects matched for sex, age, height, and mass were studied. Nineteen patients had Kellgren/Lawrence (K/L) radiographic severity grades of 1 or 2, and 23 patients had K/L grades of 3 or 4. Three-dimensional kinematics and kinetics were measured in the hip, knee, and ankle while the subjects walked at a self-selected speed. Results Patients with more severe knee OA had greater first peak knee adduction moments than their matched control subjects (P = 0.039) and than patients with less severe knee OA (P < 0.001). All patients with knee OA made initial contact with the ground with the knee in a more extended position than that exhibited by control subjects. An increased axial loading rate was present in all joints of the lower extremity. Patients with more severe knee OA had lower hip adduction moments compared with their matched control subjects. Conclusion The secondary gait changes observed among patients with knee OA reflect a potential strategy to shift the body's weight more rapidly from the contralateral limb to the support limb, which appears to be successful in reducing the load at the knee in only patients with less severe knee OA. The increased loading rate in the lower extremity joints may lead to a faster progression of existing OA and to the onset of OA at joints adjacent to the knee. Interventions for knee OA should therefore be assessed for their effects on the mechanics of all joints of the lower extremity.

The purpose of this study was to determine the contribution of changes in amplitude and phasing of medio-lateral trunk sway to a change in the knee adduction moment when walking with increased medio-lateral trunk sway. Kinematic and kinetic data of walking trials with normal and with increased trunk sway were collected for 19 healthy volunteers using a standard motion analysis system. The relationship between the change in first peak knee adduction moment (ΔKAM) and change in trunk sway amplitude (ΔSA; difference between maximum contralateral trunk lean and maximum ipsilateral trunk lean) and phasing (SP; time of heel-strike relative to time of maximum contralateral and time of maximum ipsilateral trunk lean) was determined using nonlinear regression analysis. On average, subjects increased their SA by 9.7 ± 3.6 deg (P

Objective To determine whether reducing walking speed is a strategy used by patients with knee osteoarthritis (OA) of varying disease severity to reduce the maximum knee adduction moment. Methods Self-selected walking speeds and maximum knee adduction moments of 44 patients with medial tibiofemoral OA of varying disease severity, as assessed by using the Kellgren/Lawrence grade, were compared with those of 44 asymptomatic control subjects matched for sex, age, height, and weight. Results Differences in self-selected normal walking speed explained only 8.9% of the variation in maximum knee adduction moment for the group of patients with knee OA. The severity of the disease influenced the adduction moment–walking speed relationship; the individual slopes of this relationship were significantly greater in patients with less severe OA than in asymptomatic matched control subjects. Self-selected walking speed did not differ between patients with knee OA, regardless of the severity, and asymptomatic control subjects. However, knees with more-severe OA had significantly greater adduction moments (mean ± SD 3.80 ± 0.89% body weight × height) and were in more varus alignment (6.0 ± 4.5°) than knees with less-severe OA (2.94 ± 0.70% body weight × height; and 0.0 ± 2.9°, respectively). Conclusion Patients with less-severe OA adapt a walking style that differs from that of patients with more-severe OA and controls. This walking style is associated with the potential to reduce the adduction moment when walking at slower speeds and could be linked to decreased disease severity.

The purposes of this study was to test a mechanism to reduce the knee adduction moment by testing the hypothesis that increased medio-lateral trunk sway can reduce the knee adduction moment during ambulation in healthy subjects, and to examine the possibility that increasing medio-lateral trunk sway can produce similar potentially adverse secondary gait changes previously associated with reduced knee adduction moments in patients with knee osteoarthritis. Nineteen healthy adults performed walking trials with normal and increased medio-lateral trunk sway at a self-selected normal walking speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Knee and hip adduction moments were lower (-65.0% and -57.1%, respectively) for the increased medio-lateral trunk sway trials than for the normal trunk sway trials. Knee flexion angle at heel-strike was 3 degrees higher for the increased than for the normal trunk sway trials. Knee and hip abduction moments were higher for the increased medio-lateral trunk sway trials, and none of the other variables differed between the two conditions. Walking with increased medio-lateral trunk sway substantially reduces the knee adduction moment during walking in healthy subjects without some of the adverse secondary effects such as increased axial loading rates at the major joints of the lower extremity. This result supports the potential of using gait retraining for walking with increased medio-lateral trunk sway as treatment for patients with degenerative joint disease such as medial compartment knee osteoarthritis.

Background Healthy articular cartilage is important for proper joint function. The impact of unloading due to disease or injury on healthy and diseased articular cartilage is not well understood and bed rest (BR) studies offer a unique and well-standardized model to study the effects of immobilization. Cartilage oligomeric matrix protein (COMP) is a structural protein found in cartilage and is a marker of cartilage turnover [1]. Increased serum concentrations (sCOMP) have been associated with cartilage degradation in osteoarthritis [2] and rheumatoid arthritis [3] but also physiological loading [4, 5]. sCOMP decreases with with immobilization [6]. Objectives To investigate the impact of duration of immobilization (CON) and effectiveness of exercise (INT ex) and nutrition interventions (INTnut) on sCOMP concentration in healthy male subjects during medium-term BR-studies. Methods Four BR-studies were conducted, each in cross-over design: study 1 (INTex; N=8) had a 14-days of BR, Study 2 (INTnut; N=7), Study 3 (INTnut; N=9) and Study 4 (INTex+nut; N=8) had 21 days of BR. Blood samples were taken after overnight fast. sCOMP concentration was analyzed using commercial enzyme immunoassays (COMP® ELISA, AnaMar Medical AB, Lund, Sweden). Statistical analysis (IBM SPSS Statistics, 19.01) was performed using repeated measures ANOVA (p Results BR lead to a reduction in sCOMP after 24h for all interventions and the control condition (Fig.1). sCOMP recovered to baseline after the end of BR for all conditions (study 1: INTex: +26%, CON: +28.6%; study 2: INTnut: +25%, CON: +25%; study 3: INTnut: +28.9%, CON: + 28.6%; study 4: INTex: +35.0%, INTex+nut: +33.2%, CON: +32.8%). INTnut and INTex did not affect the results. COMP data of 24 individuals from studies 1–3 were re-analyzed for the adaptation of sCOMP during BR. Baseline values of sCOMP decreased by -16% after 24h of BR and further by -5% until BRday 14. Conclusions sCOMP concentration is sensitive to immobilization. After the distinct initial decrease in sCOMP during the first 24hrs of BR, sCOMP is significantly lowered at BR day 14 compared to the first 24h of BR. These results suggest that beside a reduced diffusion of molecules from the joint, cartilage turnover is decreased during prolonged immobilization. This presumably also negatively affects tissue properties. Thus the combined effects of disease and immobilization on cartilage health in arthritis patients need to be considered and require further investigation. High standardization of blood sampling with regards to mechanical loading is essential for data quality when evaluating sCOMP concentration. References Saxne T et al.: Br J Rheumatol 1992;31: 583–91. Clark AG et al.: Arthritis Rheum. 1999;42: 2356–2364. Skoumal M et al.: Arthritis Res Ther 2004;6: 73–3. Neidhart M et al.: Osteoarthritis Cartilage. 2000;8: 222–229. Mundermann A et al.: Osteoarthritis Cartilage. 2005; 13: 34–38. Liphardt AM et al.: Osteoarthritis Cartilage 2009; 17: 1598–1603. Disclosure of Interest None declared

We tested the hypothesis that total hip arthroplasty (THA) patients have less pain and are able to walk longer post-operatively than pre-operatively, and that THA patients before and after have higher heart rates and compromised gas exchange determinants at rest and following exercise compared to healthy subjects with a post-operative improvement. Fifty-two patients completed questionnaires and an incremental walking stress test pre-operatively and 6-months after THA. Twenty-four age-matched control subjects completed the same stress test. Fifty-one patients had less pain 6-months after THA compared to pre-operative levels. Forty-three patients showed an improvement of at least one walking duration category. Patients had compromised cardiovascular fitness compared to the control group with a tendency to improve after THA. Hence, 6-months following THA, deficits exist other than reduced strength as reported in the literature. Prior to THA, the ability to walk longer is compromised by pain and not by poor cardiovascular fitness. Studies on specific rehabilitation programs of varying intensities may demonstrate opportunities to improve the cardiovascular fitness of this population.

The measurement of lower extremity alignment is an important component of the diagnosis and prognosis of musculoskeletal diseases. In addition, poor lower extremity alignment has been identified as a risk factor for incurring injuries during physical activities. Relating anthropometric information and limb alignment to joint loads during daily activities enables the identification of risk factors for musculoskeletal injuries and diseases. Lower extremity alignment can be assessed directly using medical imaging techniques or indirectly using established clinical measures. Palpation of anatomical landmarks and anthropometric information is currently used for many indirect methods assessing the alignment of the lower extremity. Current clinical methods for the measurement of lower extremity alignment include visual observation and methods using callipers, inclinometers or goniometers. A recent study showed the potential of using position capture similar to what is typically performed during gait analysis as an alternative method for the assessment of lower extremity alignment. Mechanical axis alignment assessed using this method correlated with radiographic measurements, the current gold standard, and with disease severity in patients with medial compartment knee osteoarthritis (OA). In addition, novel technology including functional joint center determination and markerless motion capture has a great potential in providing objective and thus reliable assessments of lower extremity alignment especially in populations that would not routinely undergo radiographic examination. Indirect assessment of lower extremity alignment can be challenging in obese patients and in the elderly. Establishing relationships between anthropometric information, limb alignment and detailed information measured using novel techniques is an important step in increasing the relevance of simple and quick clinical measurements for a larger range of sub-populations in health and disease.

Anthropometric characteristics, particularly body mass, are important factors in the development and progression of varus/valgus angular deformities of the knee and have long-term implications including increased risk of osteoarthritis. However, information on how excessive body weight affects the biomechanics of dynamic activities in children is limited. The purpose of this study was to test the hypothesis that during stair-walking lower extremity joint moments normalized to body mass in obese children are greater than those in normal-weight children. Eighteen obese children (10.5±1.5 years, 148±10cm, 56.6±8.4kg) and 17 normal-weight children (10.4±1.3 years, 143±9cm, 36.7±7.5kg) were recruited. A Vicon system and two AMTI force plates were used to record and analyze the kinematics and kinetics of ascending and descending stairs. Significant differences in spatio-temporal, kinematic and kinetic parameters during ascending and descending stairs between obese and normal-weight children were detected. For stair ascent, greater hip abduction moments (+23%; p=0.001) and greater knee extension moments (+20%; p=0.008) were observed. For stair descent, smaller hip extension moment (-52%; p=0.031), and greater hip flexion moments (+25%; p=0.016) and knee extension moments (+15%, p=0.008) were observed for obese subjects. To date, it is unclear if and how the body may adapt to greater joint moments in obese children. Nevertheless, these differences in joint moments may contribute to a cumulative overloading of the joint through adolescence into adulthood, and potentially result in a greater risk of developing knee and hip osteoarthritis.

The purpose of this study was to evaluate the effectiveness of variable-stiffness shoes in lowering the peak external knee adduction moment during walking in subjects with symptomatic medial compartment knee osteoarthritis. The influence on other lower extremity joints was also investigated. The following hypotheses were tested: (1) variable-stiffness shoes will lower the knee adduction moment in the symptomatic knee compared to control shoes; (2) reductions in knee adduction moment will be greater at faster speeds; (3) subjects with higher initial knee adduction moments in control shoes will have greater reductions in knee adduction moment with the intervention shoes; and (4) variable-stiffness shoes will cause secondary changes in the hip and ankle frontal plane moments. Seventy-nine individuals were tested at self-selected slow, normal, and fast speeds with a constant-stiffness control shoe and a variable-stiffness intervention shoe. Peak moments for each condition were assessed using a motion capture system and force plate. The intervention shoes reduced the peak knee adduction moment compared to control at all walking speeds, and reductions increased with increasing walking speed. The magnitude of the knee adduction moment prior to intervention explained only 11.9% of the variance in the absolute change in maximum knee adduction moment. Secondary changes in frontal plane moments showed primarily reductions in other lower extremity joints. This study showed that the variable-stiffness shoe reduced the knee adduction moment in subjects with medial compartment knee osteoarthritis without the discomfort of a fixed wedge or overloading other joints, and thus can potentially slow the progression of knee osteoarthritis.

The purpose of this study was to evaluate shoe sole material stiffness changes and angle changes that are intended to reduce the peak knee adduction moment during walking. Fourteen physically active adults were tested wearing their personal shoes (control) and five intervention pairs, two with stiffness variations, two with angle variations, and a placebo shoe. The intervention shoes were evaluated based on how much they reduced the peak knee adduction moment compared to the control shoe. An ANOVA test was used to detect differences between interventions. Linear regression analysis was used to determine a relationship between the magnitude of the knee adduction moment prior to intervention and the effectiveness of the intervention in reducing the peak knee adduction moment. Peak knee adduction moments were reduced for the altered stiffness and altered angle shoes (p < 0.010), but not for the placebo shoe (p = 0.363). Additionally, linear regression analysis showed that subjects with higher knee adduction moments prior to intervention had larger reductions in the peak knee adduction moment (p < 0.010). These results demonstrate that shoe sole stiffness and angle interventions can be used to reduce the peak knee adduction moment and that subjects with initially higher peak knee adduction moments have higher reductions in their peak knee adduction moments.

Background Moderate joint loading is essential to maintain cartilage health and function but the impact of immobilization on articular cartilage in healthy individuals is not well understood. One established biomarker for monitoring cartilage metabolism in relation to joint degeneration is cartilage oligomeric matrix protein (COMP) 1 which is sensitive to physiological loading 2-4 and 14-days of immobilization 5 . Objectives To analyze the effect of 21-days of head down tilt bed rest (HDT-BR) (Study1) and 5.5 months of microgravity (Study 2) on serum COMP concentration. Methods Study 1: Twelve healthy male subjects (34±8 yrs) participated in a 21-days HDT-BR study performed in a cross-over design. HDT-BR-only was the control (CON) condition. The intervention was resistive vibration exercise (RVE) alone or in combination with a nutrition intervention (NEX). 11 blood samples were collected before, during and after HDT-BR. Study 2: preliminary results of two astronauts will be presented. Blood samples were collected before and after 5.5 months on the International Space Station. Blood samples for both studies were taken in the morning after overnight-fast and 30 minutes supine rest. Biomarker concentrations were analyzed using commercial enzyme-linked immunosorbent assay (ELISA). Statistical analysis (IBM SPSS Statistics, 19.01) was performed using repeated measures ANOVA (p Results Study 1: Serum COMP concentration decreased with the first day of HDT (-24.7±12.5%; p Conclusions These results suggest that cartilage ECM is sensitive to unloading and immobilization may initiate catabolic processes in cartilage metabolism. Investigating cartilage health in response to a stay in microgravity is a unique model and will broaden the understanding of cartilage metabolism. Future research should investigate sufficient exercise countermeasures in order to minimize negative effects of immobilization on cartilage health. References Saxne et al. Br J Rheumatol 1992; 31(9):583-91. Neidhart et al. Osteoarthritis Cartilage 2000, 8(3):222–9. Mundermann et al. Osteoarthritis Cartilage 2005, 13(1), 34–8. Niehoff et al. Osteoarthritis Cartilage 2009, 19(8):1003-10. Liphardt et al. Osteoarthritis Cartilage 2009, 17(12):1598–603. Disclosure of Interest None declared

This review examines recent in-vivo studies of ambulation and discusses the fundamental role of mechanics of ambulation in the initiation and progression of osteoarthritis at the knee.Recent studies have supported earlier findings that a high adduction moment at the knee during ambulation was most frequently reported to influence the progression of medial compartment osteoarthritis. In contrast to previous findings in patients with osteoarthritis, recent work on healthy subjects reports that cartilage thickness increases with high ambulatory loads. Kinematic changes were associated with the initiation of osteoarthritis. Recent studies of subjects with high risk factors for knee osteoarthritis (obesity and anterior cruciate ligament injury) reported a relationship between kinematic changes during ambulation and the initiation of osteoarthritis at the knee. This review also contrasts the relative influence on osteoarthritis of knee mechanics measured during ambulatory and nonambulatory activities.The initiation of osteoarthritis occurs when healthy cartilage experiences some condition (traumatic or chronic) that causes kinematic changes during ambulation at the knee to shift the load-bearing contact location of the joint to a region not conditioned to the new loading. The rate of progression of osteoarthritis is associated with increased load during ambulation.

Osteoarthritis occurs in the majority of adults and is often described as “wear and tear” arthritis, or a disease of aging resulting from the structural and biochemical breakdown of articular cartilage in synovial joints. The causes of degenerative osteoarthritis with aging are complex and involve interrelated biological, mechanical, and structural pathways. This chapter examines the interrelationship or coupling of these pathways that converges at an in vivo systems level in humans. Using the knee as an example, an integrated in vivo framework for understanding the various factors that influence the initiation and progression of osteoarthritis is described. This framework provides a basis for explaining the role of kinematics and load on the progression of osteoarthritis. The framework helps to explain the integrated effect of biological, morphological, and neuromuscular changes to the musculoskeletal system during aging or during menopause on the increased rate of idiopathic osteoarthritis with aging.

The in vivo pathomechanics of osteoarthritis (OA) at the knee is described in a framework that is based on an analysis of studies describing assays of biomarkers, cartilage morphology, and human function (gait analysis). The framework is divided into an Initiation Phase and a Progression Phase. The Initiation Phase is associated with kinematic changes that shift load bearing to infrequently loaded regions of the cartilage that cannot accommodate the loads. The Progression Phase is defined following cartilage breakdown. During the Progression Phase, the disease progresses more rapidly with increased load. While this framework was developed from an analysis of in vivo pathomechanics, it also explains how the convergence of biological, morphological, and neuromuscular changes to the musculoskeletal system during aging or during menopause lead to the increased rate of idiopathic OA with aging. Understanding the in vivo response of articular cartilage to its physical environment requires an integrated view of the problem that considers functional, anatomical, and biological interactions. The integrated in vivo framework presented here will be helpful for the interpretation of laboratory experiments as well as for the development of new methods for the evaluation of OA at the knee.

Summary Objective To evaluate the hypothesis that a mechanical stimulus (30-min walk) will produce a change in serum concentrations of cartilage oligomeric matrix protein (COMP) that is associated with cartilage thickness changes on magnetic resonance imaging (MRI). Methods Serum COMP concentrations were measured by enzyme-linked immunosorbent assay in 17 patients (11 females, age: 59.0±9.2 years) with medial compartment knee osteoarthritis (OA) at study entry immediately before, immediately after, 3.5h, and 5.5h after a 30-min walking activity. Cartilage thickness changes in the medial femur and medial tibia were determined from MR images taken at study entry and at 5-year follow-up. Relationships between changes in cartilage thickness and COMP levels, with post-activity concentrations expressed as a percentage of pre-activity levels, were assessed by the calculation of Pearson correlation coefficients and by multiple linear regression analysis, with adjustments for age, sex, and body mass index (BMI). Results Changes in COMP levels 3.5h and 5.5h post-activity were correlated with changes in cartilage thickness in the medial femur and tibia at the 5-year follow-up. The results were strengthened after analyses were adjusted for age, sex, and BMI. Neither baseline pre-activity COMP levels nor changes in COMP levels immediately post-activity were correlated with cartilage thickness changes. Conclusions The results of this study support the hypothesis that a change in COMP concentration induced by a mechanical stimulus is associated with cartilage thinning at 5 years. Mechanically-induced changes in mechano-sensitive biomarkers should be further explored in the context of stimulus–response models to improve the ability to assess OA progression.