Physical activity as mediator between back pain and disability.

The objective was to explore the mediating role of leisure-time physical activity on the correlation between back pain and disability. A mediation analysis was conducted among the cross-sectional sample of 1330 patients in outpatient clinic. The average age was 47.6 years and 64% were women. For the entire sample, the mediating effect of physical activity remained below 10% of the total effect. The mediating effect was significantly greater among women comparing to men - up to 19.0% [95% confidence interval (CI) 10.4-27.6%] versus 2.3% (95% CI 0.0-6.1%). The effect did not significantly differ based on age, BMI, or educational or professional status. Some insignificant trends, however, could be seen - the effect was possibly stronger among patients with higher educational level and those with higher BMI. The results suggested that while physical activity seems to be a weak mediator, its mediating role might vary across different groups of patients with back pain. This variation should be taken into account when planning rehabilitation measures for people with back pain.

Sex-related differential item functioning of the Jenkins Sleep Scale: a cross-sectional study among 77 967 employees in the Finnish public sector.

OBJECTIVES: To investigate if the Jenkins Sleep Scale (JSS) demonstrates sex-related differential item functioning (DIF). DESIGN: Cross-sectional study. SETTING: Survey data from the Finnish Public Sector study (2015-2017). PARTICIPANTS: 77 967 employees in the Finnish public sector, with a mean age of 51.9 (SD 13.1) years and 82% women. OUTCOME MEASURES: Item response theory estimates: difficulty and discrimination parameters of the JSS and differences in these parameters between men and women. RESULTS: The mean JSS total score was 6.4 (4.8) points. For all four items of the JSS, the difficulty parameter demonstrated a slight shift towards underestimation of the severity of sleep difficulties. The discrimination ability of all four items was moderate to high. For the JSS composite score, overall discrimination ability was moderate (0.98, 95% CI 0.97 to 0.99). Mild uniform DIF (p<0.001) was seen: two items showed better discrimination ability among men and two others among women. CONCLUSIONS: The JSS showed overall good psychometric properties among this healthy population of employees in the Finnish public sector. The JSS was able to discriminate people with different severities of sleep disturbances. However, when using the JSS, the respondents might slightly underestimate the severity of these disturbances. While the JSS may produce slightly different results when answered by men and women, these sex-related differences are probably negligible when applied to clinical situations.

Toward Tailored Rehabilitation by Implementation of a Novel Musculoskeletal Finite Element Analysis Pipeline.

Tissue-level mechanics (e.g., stress and strain) are important factors governing tissue remodeling and development of knee osteoarthritis (KOA), and hence, the success of physical rehabilitation. To date, no clinically feasible analysis toolbox has been introduced and used to inform clinical decision making with subject-specific in-depth joint mechanics of different activities. Herein, we utilized a rapid state-of-the-art electromyography-assisted musculoskeletal finite element analysis toolbox with fibril-reinforced poro(visco)elastic cartilages and menisci to investigate knee mechanics in different activities. Tissue mechanical responses, believed to govern collagen damage, cell death, and fixed charge density loss of proteoglycans, were characterized within 15 patients with KOA while various daily activities and rehabilitation exercises were performed. Results showed more inter-participant variation in joint mechanics during rehabilitation exercises compared to daily activities. Accordingly, the devised workflow may be used for designing subject-specific rehabilitation protocols. Further, results showed the potential to tailor rehabilitation exercises, or assess capacity for daily activity modifications, to optimally load knee tissue, especially when mechanically-induced cartilage degeneration and adaptation are of interest.

Associations of Metabolic Syndrome and Its Components with the Risk of Incident Knee Osteoarthritis Leading to Hospitalization: A 32-Year Follow-up Study.

OBJECTIVES: To examine whether metabolic syndrome or its individual components predict the risk of incident knee osteoarthritis (OA) in a prospective cohort study during a 32-year follow-up period. DESIGN: The cohort consisted of 6274 participants of the Mini-Finland Health Survey, who were free from knee OA and insulin-treated diabetes at baseline. Information on the baseline characteristics, including metabolic syndrome components, hypertension, elevated fasting glucose, elevated triglycerides, reduced high-density lipoprotein, and central obesity were collected during a health examination. We drew information on the incidence of clinical knee OA from the national Care Register for Health Care. Of the participants, 459 developed incident knee OA. In our full model, age, gender, body mass index, history of physical workload, smoking history, knee complaint, and previous injury of the knee were entered as potential confounding factors. RESULTS: Having metabolic syndrome at baseline was not associated with an increased risk of incident knee OA. In the full model, the hazard ratio for incident knee OA for those with metabolic syndrome was 0.76 (95% confidence interval [0.56, 1.01]). The number of metabolic syndrome components or any individual component did not predict an increased risk of knee OA. Of the components, elevated plasma fasting glucose was associated with a reduced risk of incident knee OA (hazard ratio 0.71, 95% confidence interval [0.55, 0.91]). CONCLUSIONS: Our findings do not support the hypothesis that metabolic syndrome or its components increase the risk of incident knee OA. In fact, elevated fasting glucose levels seemed to predict a reduced risk.

Eight-year trajectories of changes in health-related quality of life in knee osteoarthritis: Data from the Osteoarthritis Initiative (OAI).

BACKGROUND: Knee osteoarthritis (OA) worsens health-related quality of life (HRQoL) but the symptom pathway varies from person to person. We aimed to identify groups of people with knee OA or at its increased risk whose HRQoL changed similarly. Our secondary aim was to evaluate if patient-related characteristics, incidence of knee replacement (KR) and prevalence of pain medication use differed between the identified HRQoL trajectory groups. METHODS: Eight-year follow-up data of 3053 persons with mild knee OA or at increased risk were obtained from the public Osteoarthritis Initiative (OAI) database. Group-based trajectory modeling was used to identify patterns of experiencing a decrease of ≥10 points (Minimal Important Change, MIC) in the Quality of Life subscale of the Knee injury and Osteoarthritis Outcome Score compared to baseline. Multinomial logistic regression, Cox regression and generalized estimating equation models were used to study secondary aims. RESULTS: Four HRQoL trajectory groups were identified. Persons in the 'no change' group (62.9%) experienced no worsening in HRQoL. 'Rapidly' (9.5%) and 'slowly' worsening (17.1%) groups displayed an increasing probability of experiencing the MIC in HRQoL. The fourth group (10.4%) had 'improving' HRQoL. Female gender, higher body mass index, smoking, knee pain, and lower income at baseline were associated with belonging to the 'rapidly worsening' group. People in 'rapidly' (hazard ratio (HR) 6.2, 95% confidence interval (CI) 3.6-10.7) and 'slowly' worsening (HR 3.4, 95% CI 2.0-5.9) groups had an increased risk of requiring knee replacement. Pain medication was more rarely used in the 'no change' than in the other groups. CONCLUSIONS: HRQoL worsening was associated with several risk factors; surgical and pharmacological interventions were more common in the poorer HRQoL trajectory groups indicating that HRQoL does reflect the need for OA treatment. These findings may have implications for targeting interventions to specific knee OA patient groups.

Health-related quality of life in relation to symptomatic and radiographic definitions of knee osteoarthritis: data from Osteoarthritis Initiative (OAI) 4-year follow-up study.

BACKGROUND: The purpose was to quantify the decrement in health utility (referred as disutility) associated with knee osteoarthritis (OA) and different symptomatic and radiographic uni- and bilateral definitions of knee OA in a repeated measures design of persons with knee OA or at increased risk of developing knee OA. METHODS: Data were obtained from the Osteoarthritis Initiative database. SF-12 health-related quality of life was converted into SF-6D utilities, and were then handled as the health utility loss by subtracting 1.000 from the utility score, yielding a negative value (disutility). Symptomatic OA was defined by radiographic findings (Kellgren-Lawrence, K-L, grade ≥ 2) and frequent knee pain in the same knee. Radiographic OA was defined by five different definitions (K-L ≥ 2 unilaterally / bilaterally, or the highest / mean / combination of K-L grades of both knees). Repeated measures generalized estimating equation (GEE) models were used to investigate disutility in relation to these different definitions. RESULTS: Utility decreased with worsening of symptomatic or radiographic status of knee OA. The participants with bilateral and unilateral symptomatic knee OA had 0.03 (p < 0.001) and 0.02 (p < 0.001) points lower utility scores, respectively, compared with the reference group. The radiographic K-L grade 4 defined as the mean or the highest grade of both knees was related to a decrease of 0.04 (p < 0.001) and 0.03 (p < 0.001) points in utility scores, respectively, compared to the reference group. CONCLUSIONS: Knee OA is associated with diminished health-related quality of life. Health utility can be quantified in relation to both symptomatic and radiographic uni- and bilateral definitions of knee OA, and these definitions are associated with differing disutilities. The performance of symptomatic definition was better, indicating that pain experience is an important factor in knee OA related quality of life.

Evaluation of the Effect of Bariatric Surgery-Induced Weight Loss on Knee Gait and Cartilage Degeneration.

The objective of the study was to investigate the effects of bariatric surgery-induced weight loss on knee gait and cartilage degeneration in osteoarthritis (OA) by combining magnetic resonance imaging (MRI), gait analysis, finite element (FE) modeling, and cartilage degeneration algorithm. Gait analyses were performed for obese subjects before and one-year after the bariatric surgery. FE models were created before and after weight loss for those subjects who did not have severe tibio-femoral knee cartilage loss. Knee cartilage degenerations were predicted using an adaptive cartilage degeneration algorithm which is based on cumulative overloading of cartilage, leading to iteratively altered cartilage properties during OA. The average weight loss was 25.7±11.0 kg corresponding to a 9.2±3.9 kg/m2 decrease in body mass index (BMI). External knee rotation moment increased, and minimum knee flexion angle decreased significantly (p < 0.05) after weight loss. Moreover, weight loss decreased maximum cartilage degeneration by 5±23% and 13±11% on the medial and lateral tibial cartilage surfaces, respectively. Average degenerated volumes in the medial and lateral tibial cartilage decreased by 3±31% and 7±32%, respectively, after weight loss. However, increased degeneration levels could also be observed due to altered knee kinetics. The present results suggest that moderate weight loss changes knee kinetics and kinematics and can slow-down cartilage degeneration for certain patients. Simulation results also suggest that prediction of cartilage degeneration is subject-specific and highly depend on the altered gait loading, not just the patient's weight.

Simulation of Subject-Specific Progression of Knee Osteoarthritis and Comparison to Experimental Follow-up Data: Data from the Osteoarthritis Initiative.

Economic costs of osteoarthritis (OA) are considerable. However, there are no clinical tools to predict the progression of OA or guide patients to a correct treatment for preventing OA. We tested the ability of our cartilage degeneration algorithm to predict the subject-specific development of OA and separate groups with different OA levels. The algorithm was able to predict OA progression similarly with the experimental follow-up data and separate subjects with radiographical OA (Kellgren-Lawrence (KL) grade 2 and 3) from healthy subjects (KL0). Maximum degeneration and degenerated volumes within cartilage were significantly higher (p < 0.05) in OA compared to healthy subjects, KL3 group showing the highest degeneration values. Presented algorithm shows a great potential to predict subject-specific progression of knee OA and has a clinical potential by simulating the effect of interventions on the progression of OA, thus helping decision making in an attempt to delay or prevent further OA symptoms.

Structure-symptom relationship with wide-area ultrasound scanning of knee osteoarthritis.

The aetiology of knee pain in osteoarthritis (OA) is heterogeneous and its relationship with structural changes and function is unclear. Our goal was to determine the prevalence of wide-area scanned ultrasound-defined knee OA structural features and their association with pain and functional impairment in 79 symptomatic and 63 asymptomatic subjects. All subjects underwent ultrasound knee wide-area scanning and the severity of articular cartilage degeneration, the presence and size of osteophytes, and meniscal extrusion were evaluated. Subjects filled in a self-administrated questionnaire on present knee pain, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) on clinical symptoms and function over the past week. Cartilage changes were the most prevalent followed by lateral meniscal extrusion, osteophytes and medial meniscal extrusion. The global femoral cartilage grade associated strongly with pain and the WOMAC index. Site-specifically, early medial cartilage changes and thinning in sulcus and lateral site were associated with symptoms. The presence of femoral lateral osteophytes was also associated with both outcomes. Using the novel wide-area ultrasound scanning technique, we were able to confirm the negative impact of femoral cartilage OA changes on clinical symptoms. Presence, not necessarily size, of lateral femoral osteophytes was also associated with increased pain and disability.

Comparison of Diagnostic Performance of Semi-Quantitative Knee Ultrasound and Knee Radiography with MRI: Oulu Knee Osteoarthritis Study.

Osteoarthritis (OA) is a common degenerative musculoskeletal disease highly prevalent in aging societies worldwide. Traditionally, knee OA is diagnosed using conventional radiography. However, structural changes of articular cartilage or menisci cannot be directly evaluated using this method. On the other hand, ultrasound is a promising tool able to provide direct information on soft tissue degeneration. The aim of our study was to systematically determine the site-specific diagnostic performance of semi-quantitative ultrasound grading of knee femoral articular cartilage, osteophytes and meniscal extrusion, and of radiographic assessment of joint space narrowing and osteophytes, using MRI as a reference standard. Eighty asymptomatic and 79 symptomatic subjects with mean age of 57.7 years were included in the study. Ultrasound performed best in the assessment of femoral medial and lateral osteophytes, and medial meniscal extrusion. In comparison to radiography, ultrasound performed better or at least equally well in identification of tibio-femoral osteophytes, medial meniscal extrusion and medial femoral cartilage morphological degeneration. Ultrasound provides relevant additional diagnostic information on tissue-specific morphological changes not depicted by conventional radiography. Consequently, the use of ultrasound as a complementary imaging tool along with radiography may enable more accurate and cost-effective diagnostics of knee osteoarthritis at the primary healthcare level.

Effectiveness of a cognitive-behavioural group intervention for knee osteoarthritis pain: a randomized controlled trial.

OBJECTIVE: To assess the effectiveness of a six week cognitive-behavioural group intervention in patients with knee osteoarthritis pain. DESIGN: Single-blinded randomized controlled trial. STUDY SETTING: Primary care providers in a medium-sized city in Finland. PATIENTS: A total of 111 participants aged from 35 to 75 with clinical symptoms and radiographic grading (Kellgren-Lawrence 2-4) of knee osteoarthritis were included. INTERVENTIONS: In the intervention group, 55 participants attended a cognitive-behavioural training programme for pain management with six weekly group sessions supervised by a psychologist and a physiotherapist. Concurrently, they and the 56 participants of the control group continued in ordinary GP care that was not altered by the study. MAIN MEASURES: The primary outcome on three-month and 12-month follow-up was the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis index pain subscale. Secondary outcome measures included self-reports of pain and physical function, health-related quality of life, and a comprehensive set of psychological questionnaires. RESULTS: Mixed model results showed no significant differences between the intervention and control group for any measures of pain or function. A significant difference between the groups was found in the Pain Self-Efficacy Questionnaire (Pr = 0.022) in favour of the control group, and in the RAND-36 emotional well-being subscale in favour of the intervention group (Pr = 0.038). Conventional group comparisons of mean follow-up values showed no significant differences in any of the outcome variables. CONCLUSION: This trial could not confirm the hypothesized advantage of a cognitive-behavioural training programme over ordinary GP care in knee osteoarthritis pain patients. TRIAL REGISTRATION: Current Controlled Trials ISRCTN64794760.

Multiple psychological factors are associated with poorer functioning in a sample of community-dwelling knee osteoarthritis patients.

BACKGROUND: Knee osteoarthritis (OA) is the most common type of arthritis and imposes a heavy burden on individual welfare among elderly people. There is preliminary evidence that psychological factors play a role in functional ability and pain in knee OA patients, particularly with respect to the surgery outcome. Less is known about psychological factors among community-dwelling patients with knee OA. OBJECTIVES: We aimed to determine which psychological factors are associated with pain and functional ability among community-dwelling knee OA patients using a comprehensive set of psychological questionnaires. METHODS: In the cross-sectional baseline setting of a prospective, randomized controlled intervention study, 111 patients aged from 35 to 75 years with clinical symptoms and radiographic grading of knee OA were included. They completed a comprehensive set of psychological questionnaires, including measures of resources and coping, fear and catastrophizing, and distress. RESULTS: In cross-sectional comparisons, pain self-efficacy, fear of movement, pain catastrophizing, and elevated anxiety were associated with pain and a poorer functional ability. In logistic regression analysis, independent association was seen between pain self-efficacy and poorer functioning. Knee OA patients also reported elevated levels of anxiety. CONCLUSIONS: The results reveal that both pain self-efficacy and negatively charged emotion and expectations toward pain are important factors when dealing with knee OA patients. Failure to consider these will probably contribute to prolonged disability and further pain. The results call for the routine assessment of multiple psychological factors in knee OA.

Nonlinear state-space modeling of human motion using 2-D marker observations.

A novel method for the estimation of human kinematics, based on state-space modeling, is proposed. The state consists of the positions, orientations, velocities, and accelerations of an articulated model. Estimation is performed using the unscented Kalman filter (UKF) algorithm with a fixed-interval smoother. Impulsive acceleration at floor contact of the foot is estimated by implementing a contact constraint in the UKF evolution model. The constraint inserts an acceleration impulse into the model state. The estimation method was applied to marker-based motion analysis in a motion laboratory. Validation measurements were performed with a rigid test device and with human gait. A triaxial accelerometer was used to evaluate acceleration estimates. Comparison between the proposed method and the extended Kalman smoother showed a clear difference in the quality of estimates during impulsive accelerations. The proposed approach enables estimation of human kinematics during both continuous and transient accelerations. The approach provides a novel way of estimating acceleration at foot initial contact, and thus enables more accurate evaluation of loading from the beginning of the floor contact.

Short-term exercise-induced improvements in bone properties are for the most part not maintained during aging in hamsters.

Physical exercise during growth affects composition, structure and mechanical properties of bone. In this study we investigated whether the beneficial effects of exercise during the early growth phase have long-lasting effects or not. Female Syrian golden hamsters (total n=152) were used in this study. Half of the hamsters had access to running wheels during their rapid growth phase (from 1 to 3months of age). The hamsters were sacrificed at the ages of 1, 3, 12, and 15months. The diaphysis of the mineralized humerus was analyzed with microCT and subjected to three-point-bending mechanical testing. The trabecular bone in the tibial metaphysis was also analyzed with microCT. The collagen matrix of the humerus bone was studied by tensile testing after decalcification. The weight of the hamsters as well as the length of the bone and the volumetric bone mineral density (BMDvol) of the humerus was higher in the running group at the early age (3months). Moreover, the mineralized bone showed improved mechanical properties in humerus and had greater trabecular thickness in the subchondral bone of tibia in the runners. However, by the age of 12 and 15months, these differences were equalized with the sedentary group. The tensile strength and Young's modulus of decalcified humerus were higher in the runners at early stage, indicating a stronger collagen network. In tibial metaphysis, trabecular thickness was significantly higher for the runners in the old age groups (12 and 15months). Our study demonstrates that physical exercise during growth improves either directly or indirectly through weight gain bone properties of the hamsters. However, the beneficial effects were for the most part not maintained during aging.

Lower impulsive loadings following intensive weight loss after bariatric surgery in level and stair walking: a preliminary study.

BACKGROUND: There are currently very few of studies which have evaluated the role of bariatric surgery in joint loadings and changes in gait. We wanted to examine how impulsive loading would change level and stair walking in severely or morbidly obese subjects after they had undergone bariatric surgery and weight loss. METHODS: Thirteen female and three male adults aged between 30 and 63 years, cleared for Roux-en-Y gastric bypass, were recruited into this study. All subjects were severely or morbidly obese i.e., body mass index was >35 kg/m(2). The measurement methods consisted of triaxial skin mounted accelerometers and ground reaction force (GRF); conducted at two different predetermined gait speeds. RESULTS: The average weight loss was 27.4 (SD8.7) kg after 8.8 (SD3.9) months of follow-up period. Most of the absolute GRF parameters decreased in proportion to weight loss. However, medio-lateral GRF parameters decreased more than expected. The general trend in the knee accelerations demonstrated lower impulsive loadings in both axial and horizontal directions after weight loss. We did not observe any significant changes in stair walking. CONCLUSIONS: Weight loss after bariatric surgery not only induces a simple mass-related adaptation in gait but also achieves mechanical plasticity in gait strategy.

Effectiveness of a cognitive-behavioral group intervention for knee osteoarthritis pain: protocol of a randomized controlled trial.

BACKGROUND: Knee osteoarthritis is the most common type of arthritis, with pain being its most common symptom. Little is known about the psychological aspects of knee osteoarthritis pain. There is an emerging consensus among osteoarthritis specialists about the importance of addressing not only biological but also psychosocial factors in the assessment and treatment of osteoarthritis. As few studies have evaluated the effect of psychological interventions on knee osteoarthritis pain, good quality randomized controlled trials are needed to determine their effectiveness. METHODS/DESIGN: We intend to conduct a 6-week single-blinded randomized controlled trial with a 12-month follow-up. Altogether, 108 patients aged from 35 to 75 years with clinical symptoms and radiographic grading (KL 2-4) of knee osteoarthritis will be included. The clinical inclusion criteria are pain within the last year in or around the knee occurring on most days for at least one month, and knee pain of ≥ 40 mm on a 100-mm visual analogue scale in the WOMAC pain subscale for one week prior to study entry. Patients with any severe psychiatric disorder, other back or lower limb pain symptoms more aggravating than knee pain, or previous or planned lower extremity joint surgery will be excluded. The patients will be randomly assigned to a combined GP care and cognitive-behavioral intervention group (n = 54) or to a GP care control group (n = 54). The cognitive-behavioral intervention will consist of 6 weekly group sessions supervised by a psychologist and a physiotherapist experienced in the treatment of pain. The main goals of the intervention are to reduce maladaptive pain coping and to increase the self-management of pain and disability. The follow-up-points will be arranged at 3 and 12 months. The primary outcome measure will be the WOMAC pain subscale. Secondary outcome measures will include self-reports of pain and physical function, a health related quality of life questionnaire, and various psychological questionnaires. Personnel responsible of the data analysis will be blinded. DISCUSSION: This study addresses the current topic of non-pharmacological conservative treatment of knee OA-related pain. We anticipate that these results will provide important new insights to the current care recommendations. TRIAL REGISTRATION: Current Controlled Trials ISRCTN64794760.

Determinants of pain and functioning in hip osteoarthritis - a two-year prospective study.

OBJECTIVE: To identify predictors of pain and disability in hip osteoarthritis. DESIGN: A prospective analysis of determinants of pain and functioning in hip osteoarthritis. STUDY SETTING: Rehabilitation clinic in a central hospital. PATIENTS: A total of 118 men and women aged 55-80 years who had radiologically diagnosed hip osteoarthritis and associated clinical symptoms and participated in a randomized controlled trial. MAIN MEASURES: The self-reported disease-specific pain and physical function were assessed using the pain and functioning subscales of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis index. The self-reported generic physical and mental functioning were assessed by using the Finnish-validated SF-36-item Health Survey RAND-36 subscales for function and physical and mental component summary scores. Outcome measures were recorded at 0, 3, 6, 12, 18 and 24 months. RESULTS: Multivariate linear mixed model analyses revealed that lower disease-specific pain score and better functioning (WOMAC) were predicted by higher educational level (9.61 (3.15 to 16.07); 9.07 (2.05 to 16.09)), supervised exercise training (-10.13 (-17.87 to -2.39); -11.58 (-19.40 to -3.77)), habitual conditioning physical activity (-0.48 (-0.96 to -0.01); -0.39 (-0.84 to 0.05)), absence of comorbidities (-6.30 (-12.35 to -0.24); -7.87 (-14.45 to -1.30)) and absence of additional knee osteoarthritis (-7.62 (-13.87 to -1.36); -8.02 (-14.81 to -1.23)), respectively. The same factors, except for the comorbidities, also predicted general physical functioning score (RAND-36). CONCLUSIONS: Higher education, absence of knee osteoarthritis and comorbidities, supervised exercise training and habitual conditioning physical activity predicted a lower presence of pain and better functional status in patients with hip osteoarthritis.

Kinematic and kinetic changes in obese gait in bariatric surgery-induced weight loss.

This study examines the effects of a radical bariatric surgery-induced weight loss on the gait of obese subjects. We performed a three-dimensional motion analysis of lower limbs, and collected force platform data in the gait laboratory to calculate knee and hip joint moments. Subjects (n=13) performed walking trials in the laboratory before and 8.8 months (SD 4.2) after the surgical procedure at two gait speeds (1.2m/s and 1.5m/s). The average weight loss was 26.7kg (SD 9.2kg), corresponding to 21.5% (SD 6.8%) of the initial weight. We observed a decrease in step width at both gait speeds, but no changes in relative double support or swing time or stride length. A significant decrease was noted in the absolute values of peak knee abductor, peak knee flexor and peak hip extensor moments. However, the moment values normalized by the body weight and height remained unchanged in most cases. Thus, we conclude that weight loss reduces hip and knee joint moments in proportion to the amount of weight lost.

Minor influence of lifelong voluntary exercise on composition, structure, and incidence of osteoarthritis in tibial articular cartilage of mice compared with major effects caused by growth, maturation, and aging.

We investigated the effects of lifelong voluntary exercise on articular cartilage of mice. At the age of 4 weeks C57BL mice (n = 152) were divided into two groups, with one group serving as a sedentary control whereas the other was allowed free access to a running wheel from the age of 1 month onward. Mice were euthanized at four different time points (1, 2, 6, and 18 months of age). Articular cartilage samples were gathered from the load-bearing area of the tibial medial plateaus, and osteoarthritis was graded. Additionally, the proteoglycan content distribution was assessed using digital densitometry, collagen fibril orientation, and parallelism with polarized light microscopy, and collagen content using Fourier transform infrared imaging spectroscopy. The incidence of osteoarthritis increased with aging, but exercise had no effect on this trend. Furthermore, the structure and composition revealed significant growth, maturation, and age-dependent properties. Exercise exerted a minor effect on collagen fibril orientation in the superficial zone. Fibril orientation at 2 months of age was more perpendicular to surface (p < 0.05) in controls compared with runners, whereas the situation was reversed at the age of 18 months (p < 0.05). The collagen content of the superficial zone was higher (p < 0.01) at the age of 18 months in controls compared with runners but the proteoglycan content did not display any exercise-dependent changes. In conclusion, growth, maturation, and aging exerted a clear effect on integrity, structure, and composition of medial tibial plateau articular cartilage in mice, whereas lifelong voluntary exercise had only a minor effect on collagen architecture and content.