Association of physical performance with muscle strength and hip range of motion in hip osteoarthritis

Objective

To examine whether the associations of physical performance with isometric hip and knee extensors strength and passive hip flexion and internal rotation range of motion (ROM) are nonlinear in community‐dwelling adults with hip osteoarthritis (OA).

Methods

Participants were 100 adults (mean age 62 years) with radiographically confirmed hip OA. Physical performance measures included gait speed test and timed stair tests. Piecewise regression models of muscle strength and hip ROM on physical performance measures were used to identify possible breakpoints. Receiver operating characteristic (ROC) curve analysis was used to identify participants with functionally inadequate (≤1.0 meters/second) gait speed and optimal cut points were identified.

Results

Muscle strength and hip ROM were nonlinearly associated with stair measures but not with gait speed measures. The optimal breakpoints and ROC‐derived cut points were 1.8–2.5Nm/kg for knee extensors, 1.5–2.1Nm/kg for hip extensors, 25–26° for hip internal rotation ROM, and 109–115° for hip flexion ROM. Muscle strength breakpoints increased monotonically with increasing movement demand.

Conclusion

In individuals with hip OA, the associations between physical performance and measures of muscle strength and hip ROM are less straightforward than previously assumed. These breakpoints and ROC‐derived cut points may be useful in identifying individuals for whom interventions that improve muscle strength or hip ROM would be most beneficial.     

Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort

Objective

To assess whether knee extensor strength or hamstring:quadriceps (H:Q) ratio predicts risk for incident radiographic tibiofemoral and incident symptomatic whole knee osteoarthritis (OA) in adults ages 50–79 years.

Methods

We followed 1,617 participants (2,519 knees) who, at the baseline visit of the Multicenter Osteoarthritis (MOST) Study, did not have radiographic tibiofemoral OA and 2,078 participants (3,392 knees) who did not have symptomatic whole knee OA (i.e., did not have the combination of radiographic OA and frequent knee symptoms). Isokinetic strength was measured at baseline, and participants were followed for development of incident radiographic tibiofemoral OA, or incident symptomatic whole knee OA at 30 months. Generalized estimating equations accounted for 2 knees per subject, and multivariable models adjusted for age, body mass index (BMI), hip bone mineral density, knee surgery or pain, and physical activity score.

Results

In the studies of incident radiographic and incident symptomatic knee OA, mean ± SD ages were 62.4 ± 8.0 years and 62.3 ± 8.0 years, respectively, and mean ± SD BMI scores were 30.6 ± 5.8 kg/m² and 30.2 ± 5.5 kg/m², respectively. Knee extensor strength and H:Q ratio at baseline significantly differed between men and women. Neither knee extensor strength nor the H:Q ratio was predictive of incident radiographic tibiofemoral OA. Compared with the lowest tertile, the highest tertile of knee extensor strength protected against development of incident symptomatic whole knee OA in both sexes (adjusted odds ratio 0.5–0.6). H:Q ratio was not predictive of incident symptomatic whole knee OA in either sex.

Conclusion

Thigh muscle strength does not appear to predict incident radiographic OA, but does seem to predict incident symptomatic knee OA.     

Quadriceps muscle weakness after anterior cruciate ligament reconstruction: A risk factor for knee osteoarthritis?

Objective

To identify risk factors for knee osteoarthritis (OA) 10–15 years after anterior cruciate ligament (ACL) reconstruction. We hypothesized that quadriceps muscle weakness after ACL reconstruction would be a risk factor for radiographic and symptomatic radiographic knee OA 10–15 years later.

Methods

Subjects with ACL reconstruction (n = 258) were followed for 10–15 years. Subjects with unilateral injury at the 10–15‐year followup were included in the present study. Outcomes included the Cincinnati knee score, knee joint laxity, hop performance, and isokinetic muscle strength tests at 6 months, 1 year, and 2 years postoperatively. At the 10–15‐year followup, radiographs were taken and graded according to the Kellgren/Lawrence classification (range 0–4).

Results

Of the 212 subjects (82%) assessed at the 10–15‐year followup, 164 subjects had unilateral injury. The mean ± SD age at ACL reconstruction was 27.4 ± 8.5 years. Increased age (odds ratio [OR] 1.06, 95% confidence interval [95% CI] 1.01–1.11) and meniscal injury and/or chondral lesion (OR 2.05, 95% CI 1.00–4.20) showed significantly higher odds for radiographic knee OA. Low self‐reported knee function 2 years postoperatively (OR 0.95, 95% CI 0.92–0.98) and loss of quadriceps strength between the 2‐year and the 10–15‐year followup (OR 1.00, 95% CI 1.00–1.01) showed significantly higher odds for symptomatic radiographic knee OA. Quadriceps muscle weakness after ACL reconstruction was not significantly associated with knee OA.

Conclusion

This study detected no association between quadriceps weakness after ACL reconstruction and knee OA as measured 10–15 years later.     

Pelvic and Hip Kinematics During Walking in People With Patellofemoral Joint Osteoarthritis Compared to Healthy Age‐Matched Controls

Objective

Patellofemoral (PF) joint osteoarthritis (OA) is common, yet little is known about how this condition influences lower‐extremity biomechanical function. This study compared pelvis and lower‐extremity kinematics in people with and without PF joint OA.

Methods

Sixty‐nine participants (64% women, mean ± SD age 56 ± 10 years) with anterior knee pain aggravated by PF joint–loaded activities (e.g., stair ambulation, rising from sitting, or squatting) and radiographic lateral PF joint OA on skyline radiographs were compared with 18 controls (78% women, mean ± SD age 53 ± 7 years) with no lower‐extremity pain or radiographic OA. Knee Injury and Osteoarthritis Outcome Score (KOOS) data were collected from participants with PF joint OA. Quantitative gait analyses were conducted during overground walking at a self‐selected speed. Pelvis and lower‐extremity kinematics were calculated across the stance phase. Data were statistically analyzed using analyses of covariance, with age and sex as covariates (P < 0.05).

Results

Participants with PF joint OA reported a mean ± SD KOOS pain subscale score of 65 ± 15, KOOS symptoms subscale score of 63 ± 16, KOOS activities of daily living subscale score of 73 ± 13, KOOS sports/recreation subscale score of 45 ± 23, and KOOS quality of life subscale score of 43 ± 16. Participants with PF joint OA walked with greater anterior pelvic tilt throughout the stance phase, as well as greater lateral pelvic tilt (i.e., pelvis lower on the contralateral side), greater hip adduction, and lower hip extension during the late stance phase. No differences in knee and ankle joint angles were observed between groups.

Conclusion

People with PF joint OA walk with altered pelvic and hip movement patterns compared with aged‐matched controls. Restoring normal movement patterns during walking in people with PF joint OA may be warranted to help alleviate symptoms.

     

Individuals with severe knee osteoarthritis (OA) exhibit altered proximal walking mechanics compared with individuals with less severe OA and those without knee pain

Objective

To examine hip, pelvis, and trunk walking biomechanics in individuals with medial compartment knee osteoarthritis (OA) of varying radiographic disease severities and others without knee pain.

Methods

Hip, pelvis, and trunk kinematics and hip kinetics were assessed in 75 individuals with radiographically confirmed OA and 20 asymptomatic individuals. Differences in peak hip adduction and abduction angles, the amount of contralateral pelvic drop, and peak lateral trunk lean measured by 3‐dimensional gait analysis were examined using analyses of variance. Peak external hip abduction and adduction moments were compared using analyses of covariance, with gait speed as a covariate.

Results

Those with severe OA disease exhibited significantly less peak hip adduction (5.0°), but more ipsilateral trunk lean toward the study extremity (5.0°) than all other groups (P < 0.001). Those in the severe (1.1°) and asymptomatic (0.9°) groups also exhibited significantly less lateral trunk lean toward the non‐study extremity (P = 0.004). No significant differences in hip joint moments or contralateral pelvic drop were observed between the groups (P > 0.02).

Conclusion

Gait changes at the hip and trunk were evident across the groups based on radiographic disease severity and compared with those without knee pain. Although not conclusive from this cross‐sectional study design, the results provide initial evidence to support increased lateral trunk lean as being a compensatory response to the disease.     

Does hand osteoarthritis predict future hip or knee osteoarthritis?

Objective

To evaluate the risk of future hip or knee osteoarthritis (OA) in subjects with hand OA at baseline and to evaluate whether the concurrent presence of hand OA, other risk factors for OA, or an OA biomarker (type II collagen C‐telopeptide degradation product [CTX‐II]) further increases the risk.

Methods

Radiographs of the hands (baseline) and the hips and knees (baseline and 6.6 years later) were obtained in a randomly selected subset of participants in the Rotterdam Study who were ages 55 years and older. Radiographs were scored for the presence of OA using the Kellgren/Lawrence (K/L) system. A total of 1,235 subjects without OA of the hip/knee (K/L score 0–1) at baseline were included in the study. CTX‐II levels were measured at baseline. The independent risk of future hip/knee OA in subjects with hand OA at baseline was assessed by logistic regression, as stratified for age, sex, body mass index, family history of OA, and heavy workload.

Results

Overall 12.1% of the participants (19.7% of those with hand OA versus 10.0% of those without) developed hip or knee OA (odds ratio [OR] 2.1 [95% confidence interval (95% CI) 1.3–3.1]). Subjects with hand OA had an increased risk of future hip OA (OR 3.0 [95% CI 1.6–5.4]), which was further increased in those with a family history of OA. Subjects with hand OA had an OR of 1.6 [95% CI 1.0–2.8) for the future development of knee OA, which was further increased in those who were overweight. Concurrent hand OA and high levels of CTX‐II further increased the risk of having hip or knee OA at followup (OR 4.2 [95% CI 2.3–7.8]).

Conclusion

The presence of hand OA at baseline showed an increased risk of future hip/knee OA (higher for hip OA than for knee OA). The concurrent presence of hand OA and other OA risk factors or high CTX‐II levels further increased the risk of future hip/knee OA.

     

Physical activity and incident clinical knee osteoarthritis in older adults

Objective

To study the relationship between 4 components of physical activity and the 12‐year incidence of clinical knee osteoarthritis (OA) among older adults.

Methods

Longitudinal data from 1,678 men and women, ages 55–85 years, were collected in the Longitudinal Aging Study Amsterdam. Incident clinical knee OA was defined by an algorithm using self‐report and general practitioner data. Physical activity was assessed by a validated questionnaire from which 4 physical activity component scores were created: muscle strength, intensity, mechanical strain, and turning actions. Cox proportional hazards models were conducted to examine the relationship between these scores and incident knee OA and reported as hazard ratios (HRs) with 95% confidence intervals (95% CIs).

Results

During 12 years of followup, 463 respondents (28%) developed clinical knee OA. A high mechanical strain score (HR 1.43, 95% CI 1.15–1.77) and a low muscle strength score (HR 1.30, 95% CI 1.01–1.68) were associated with an increased risk of knee OA after adjustment for age, sex, region of living, education, lifetime physical work demands, lifetime general physical activity, body mass index, current total physical activity level, and depression. No association was observed in the intensity and turning actions components. The results were similar for men and women, and for obese and nonobese respondents.

Conclusion

Older adults who perform low muscle strength activities or activities causing high mechanical strain had an increased risk of clinical knee OA. These results suggest that specific components of physical activity may influence the development of knee OA.     

Can patellar tape reduce the patellar malalignment and pain associated with patellofemoral osteoarthritis?

Objective

Patellar taping is a conservative treatment that may reduce patellar malalignment and pain in people with patellofemoral joint osteoarthritis (OA). This study aimed to compare patellar alignment in people with and without patellofemoral joint OA and to evaluate immediate effects of patellar taping on patellar alignment and pain in people with patellofemoral joint OA.

Methods

Patellar malalignment was measured from magnetic resonance imaging (MRI; 15° knee flexion) in 28 individuals (14 with patellofemoral joint OA and 14 asymptomatic, age‐matched controls). In the patellofemoral joint OA group, MRI data were collected in 2 randomly allocated conditions (tape and no tape). Patellar alignment indices were measured from deidentified axial scans by 1 examiner. Pain during squatting was recorded in the 2 conditions (tape and no tape).

Results

People with patellofemoral joint OA exhibited greater lateral displacement and bisect offset compared with controls (P < 0.001). Lateral patellar tilt angle did not differ between groups. In the patellofemoral joint OA group, patellar tape resulted in a significant lessening of lateral alignment, with reduced lateral displacement (P = 0.028) and increased lateral patellar tilt angle (P < 0.001). Mean pain during squatting decreased with patellar tape by 15 mm on a 100‐mm scale (P = 0.045).

Conclusion

Patellar tape may reduce malalignment and pain associated with patellofemoral joint OA.     

Association of lower muscle strength with self-reported knee instability in osteoarthritis of the knee: results from the Amsterdam Osteoarthritis cohort

Objective

To determine whether muscle strength, proprioceptive accuracy, and laxity are associated with self‐reported knee instability in a large cohort of knee osteoarthritis (OA) patients, and to investigate whether muscle strength may compensate for impairment in proprioceptive accuracy or laxity, in order to maintain knee stability.

Methods

Data from 283 knee OA patients from the Amsterdam Osteoarthritis cohort were used. Univariable and multivariable logistic regression analyses were performed to assess the association between muscle strength, proprioceptive accuracy (motion sense), frontal plane varus–valgus laxity, and self‐reported knee instability. Additionally, effect modification between muscle strength and proprioceptive accuracy and between muscle strength and laxity was determined.

Results

Self‐reported knee instability was present in 67% of the knee OA patients and mainly occurred during walking. Lower muscle strength was significantly associated with the presence of self‐reported knee instability, even after adjusting for relevant confounding. Impaired proprioceptive accuracy and high laxity were not associated with self‐reported knee instability. No effect modification between muscle strength and proprioceptive accuracy or laxity was found.

Conclusion

Lower muscle strength is strongly associated with self‐reported knee instability in knee OA patients, while impairments in proprioceptive accuracy and laxity are not. A compensatory role of muscle strength for impaired proprioceptive accuracy or high laxity, in order to stabilize the knee, could not be demonstrated.     

Knee laxity after staircase exercise predicts radiographic disease progression in medial compartment knee osteoarthritis

Objective

To evaluate whether increased laxity of the knee during daily physical activities such as stair climbing is associated with progression of knee joint osteoarthritis (OA).

Methods

During the years 2001–2003, 136 patients with bilateral primary medial compartment knee joint OA were enrolled in this prospective study. Baseline data collected were body mass index (BMI), muscle power, radiographic joint space width, mechanical axis on standing radiography, and anteroposterior (AP) knee laxity before and after physical exercise. After 8 years of followup, 84 patients were reexamined to assess radiographic changes. Radiographic disease progression was defined as progression of >1 grade on the Kellgren/Lawrence scale.

Results

AP knee laxity increased significantly after stair climbing. Patients with OA progression and those without progression did not differ significantly in age, sex, baseline quadriceps muscle strength, mechanical axis, joint space width, and AP knee laxity before exercise. The 2 groups of patients did, however, differ significantly in baseline BMI and change in AP knee laxity due to exercise. The risk of progression of knee OA increased 4.15‐fold with each millimeter of increase in the change in AP knee laxity due to exercise and 1.24‐fold with each point increase in the BMI.

Conclusion

Our results indicate that patients with OA progression have significantly greater changes in knee joint laxity during physical activities and a higher BMI than patients without OA progression. These findings suggest that larger changes in knee laxity during repetitive physical activities and a higher BMI play significant roles in the progression of knee OA.

     

Night pain in hip and knee osteoarthritis: A focus group study

Objective

To explore the experience of night pain in people with hip or knee osteoarthritis (OA).

Methods

Twenty‐eight focus groups were conducted in 6 centers in 4 countries, with a total of 130 men and women with hip or knee OA. Two focus groups were excluded from the analysis, leaving 26 groups comprising 123 participants. Sampling was performed to ensure approximately equal representation of individuals with mild, moderate, and severe pain, hip OA, and knee OA. Format and methodology were standardized across centers, and participants described and discussed their experience of night pain. The focus groups were audio‐recorded and transcribed. Data were analyzed by identifying emergent codes that were grouped and compared, resulting in the identification of key themes.

Results

The majority of participants (81%) experienced night pain; the remaining 19%, who reported no night pain, were from the moderate or severe pain focus groups. Similar night pain experiences were expressed by the hip and knee OA participants. Night pain was also present regardless of the stage of OA, but severity increased as the disease progressed. Night pain was variable and intermittent. Three key themes were identified: prediction of night pain, sleep disturbance, and adaptations and treatment regimens.

Conclusion

Due to its variability and complexity, the assessment of night pain should take into account the importance of the patient narrative. Also, night pain may not be a distinct marker of disease severity, and this may have implications for its use as a priority indicator for total joint replacement.     

Varus–valgus laxity and passive stiffness in medial knee osteoarthritis

Objective

To compare differences in knee varus and valgus angular laxity and passive mechanical stiffness between asymptomatic knees and those with mild, moderate, and severe knee osteoarthritis (OA).

Methods

A total of 127 participants with symptomatic medial tibiofemoral OA and 32 asymptomatic controls participated. OA knees were stratified according to radiographic severity. Varus–valgus laxity was evaluated using a customized dynamometer, providing continuous measurement of varus–valgus joint angle and torque. The following indices were calculated: 1) varus, valgus, and total angular laxity, 2) end‐range varus and valgus stiffness, and 3) midrange stiffness.

Results

There was no difference in varus, valgus, and total angular laxity, or varus and valgus end‐range stiffness between the groups (P > 0.05 for all). The OA groups were less stiff in the midrange compared with the controls (P = 0.004–0.043).

Conclusion

The absence of differences in total angular laxity is contrary to previous findings, and may be associated with the failure of previous work to account for body size effects. Less midrange stiffness in OA participants compared with controls may indicate less rotational support provided by passive joint structures in knee OA within the functionally important range. The role of passive varus–valgus stiffness in disease onset and progression is worthy of further investigation.     

Associations for change in physical and psychological factors and treatment response following exercise in knee osteoarthritis: An exploratory study

Objective

Understanding how changes in physical and psychological factors following therapeutic exercise are associated with treatment outcome could have important implications for refining rehabilitation programs for knee osteoarthritis (OA). The objective of this study was to examine the association of changes in these factors with changes in pain and function after an exercise program for people with knee OA.

Methods

In total, 152 people with knee OA completed an exercise program consisting of lower extremity strengthening, stretching, range of motion, balance and agility, and aerobic exercises. The change from baseline to the 2‐month followup was calculated for physical and psychological factors, including self‐reported knee instability, quadriceps strength, knee and ankle range of motion, lower extremity muscle flexibility, fear of physical activity, anxiety, and depressive symptoms. Treatment response was defined as a minimum of a 20% improvement from baseline in both a numerical knee pain rating scale and the Western Ontario and McMaster Universities Osteoarthritis Index physical function scale. The association of each factor with treatment response was examined with logistic regression mutually adjusted for age, sex, body mass index, radiographic severity, and exercise group.

Results

Change in self‐reported knee instability (odds ratio [OR] 1.67 [95% confidence interval (95% CI) 1.13–2.47]) and fear of physical activity (OR 0.93 [95% CI 0.88–1.00]) were the only 2 factors that were significantly associated with treatment response after adjustment for covariates.

Conclusion

Improvement in knee instability and fear of physical activity were associated with increased odds of a positive treatment response following therapeutic exercise in subjects with knee OA.     

Self‐report and physical performance measures of physical function in hip osteoarthritis: Relationship to isometric quadriceps torque development

Objective

Quadriceps strength (knee extensor torque) is an important correlate of physical function in individuals with hip osteoarthritis (OA). However, it remains unclear whether the ability to rapidly generate quadriceps torque in the early phase of muscle contraction (maximal rate of torque development [MRTD]) is also associated with physical function. The purpose of this study was to quantify the independent impact of quadriceps strength and quadriceps MRTD on self‐report and physical performance measures of physical function in community‐dwelling adults with hip OA.

Methods

Ninety‐two adults with radiographically confirmed symptomatic hip OA (mean age 62 years) participated. Unilateral isometric quadriceps strength and MRTD were measured using a dynamometer. Self‐report measure of physical function was assessed by the Short Form 36 (SF‐36) questionnaire, and physical performance was assessed by the timed stair and step tests.

Results

In the hierarchical regression models, high maximal quadriceps strength and high quadriceps MRTD uniquely covaried with high SF‐36 physical function scores after accounting for demographic, anthropometric, and pain measures. For the timed stair test, all else being equal, in 2 participants with low but identical levels of quadriceps strength, the one with a higher MRTD had better stair‐climbing function. For the step test, quadriceps MRTD was not associated with step test performance over and above that of quadriceps strength.

Conclusion

In individuals with hip OA, maximal quadriceps strength and quadriceps MRTD positively impact self‐report and physical performance measures of physical function. These findings are of importance in developing intervention strategies, but they call for further study.     

Impact of Osteoarthritis on Difficulty Walking: A Population‐Based Study

Objective

To assess the relationship of hip and knee osteoarthritis (OA) to walking difficulty.

Methods

A population cohort ages ≤55 years recruited from 1996 to 1998 (n = 28,451) completed a standardized questionnaire assessing demographics, health conditions, joint symptoms, and functional limitations, including difficulty walking in the past 3 months. Survey data were linked to health administrative databases; self‐report and administrative data were used to identify health conditions. Hip/knee OA was defined as self‐reported swelling, pain, or stiffness in a hip or knee lasting ≥6 weeks in the past 3 months without an inflammatory arthritis diagnosis. Using multivariable logistic regression, we examined the determinants of walking difficulty and constructed a clinical nomogram.

Results

A total of 18,490 cohort participants were eligible (mean age 68 years, 60% women), and 25% reported difficulty walking. Difficulty walking was significantly and independently associated with older age, female sex, body mass index, and several health conditions. Of the conditions examined, the likelihood of walking difficulty was greatest with hip and knee OA and increased with the number of hip/knee joints affected. The predicted probability of difficulty walking for a 60‐year‐old middle‐income, normal‐weight woman was 5–10% with no health conditions, 10–20% with diabetes mellitus and cardiovascular (CV) disease, 40% with OA in 2 hips/knees, 60–70% with diabetes mellitus, CV disease, and OA in 2 hips/knees, and 80% with diabetes mellitus, CV disease, and OA in all hips/knees.

Conclusion

In a population cohort, symptomatic hip/knee OA was the strongest contributor to walking difficulty. Given the importance of walking to engagement in physical activity for chronic disease management, greater attention to OA is warranted.     

Muscle mass,muscle strength,functional performance,and physical impairment in women with the hypermobility type of Ehlers‐Danlos syndrome

Objective

To investigate lower extremity muscle mass, muscle strength, functional performance, and physical impairment in women with the Ehlers‐Danlos syndrome hypermobility type (EDS‐HT).

Methods

Forty‐three women with EDS‐HT and 43 sex‐ and age‐matched healthy control subjects participated. Muscle mass was determined by dual x‐ray absorptiometry. Muscle strength and muscle strength endurance were measured with isokinetic dynamometry at angular velocities of 60, 180, and 240°/second. Static muscle endurance during posture maintenance was also assessed. Pain and fatigue were simultaneously evaluated by visual analog scale and the Borg scale, respectively. In addition, the chair rise test for assessment of functional performance and the Arthritis Impact Measurement Scales (AIMS) for physical impairment evaluation were used.

Results

Compared to control subjects, EDS‐HT patients showed substantial lower extremity muscle weakness, reflected by significantly reduced knee extensor and flexor muscle strength and endurance parameters, with differences ranging from ?30% to ?49%; reduced static muscle endurance time; and diminished functional performance. Lower extremity muscle mass was similar in both groups and unlikely to affect the muscle strength results. By contrast, pain and fatigue were omnipresent and increased remarkably due to the tests. Furthermore, the EDS‐HT group was physically impaired, especially in the AIMS domain walking and bending.

Conclusion

This study demonstrates severely reduced quantitative muscle function and impairment in physical function in patients with EDS‐HT compared to age‐ and sex‐matched controls. The muscle weakness may be due to muscle dysfunction rather than reduced muscle mass. Whether muscle strength and endurance can be improved by appropriate exercise programs needs evaluation in further studies.

     

Thigh muscle strength,functional capacity,and self‐reported function in patients at high risk of knee osteoarthritis compared with controls

Objective

Reduced muscle strength is suggested as a risk factor for knee osteoarthritis (OA). Meniscectomy patients have an increased risk of developing knee OA. The aim of this study was to identify reductions in different aspects of muscle strength as well as objectively measured and self‐reported lower extremity function in middle‐aged patients who had undergone a meniscectomy compared with controls.

Methods

Thirty‐one patients who had undergone surgery in 2006 and 2007 (mean ± SD age 46 ± 6 years, mean ± SD body mass index [BMI] 26 ± 4 kg/m², and mean ± SD postsurgery 21 ± 6 months) and 31 population‐based controls (mean ± SD age 46 ± 6 years and mean ± SD BMI 26 ± 4 kg/m²) were examined for maximal muscle strength and rapid force capacity, distance achieved during the one‐leg hop test, and the maximum number of knee bends performed in 30 seconds. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to determine self‐reported outcomes.

Results

No differences were detected in any muscle strength variables between the operated and nonoperated leg (mean ± SD quadriceps maximum voluntary contraction of 2.80 ± 0.10 for the operated leg and 2.88 ± 0.10 for the nonoperated leg), between patients and controls (mean ± SD torque of 2.70 ± 0.09 Nm × kg^‐1 for the controls; P = 0.26 for main effect leg), or in objectively measured function (P ≥ 0.27). Patients reported 10–26 points worse KOOS scores in all 5 subscales (P < 0.001).

Conclusion

Thigh muscle strength is not impaired in middle‐aged adults 2 years after resection of a degenerative tear. Our findings indicate that factors other than muscle strength are responsible for the perceived functional limitations and suggest that training to improve strength alone may not be sufficient to improve self‐reported function in patients at high risk of knee OA.     

The osteoarthritis knowledge scale

Objective

Accurate knowledge is central to effective self-care of osteoarthritis (OA). This study aimed to assess the measurement properties of the Osteoarthritis Knowledge Scale (OAKS) with versions for the hip and knee.

Methods

Participants with hip OA (n = 144), knee OA (n = 327), and no OA (n = 735) were recruited. Rasch analysis was conducted to assess psychometric properties using data from all participants with hip OA and 144 randomly selected participants with either knee OA or no OA. Test-retest reliability and measurement error were estimated among those with hip (n = 51) and knee (n = 142) OA.

Results

Four items from the draft scales were deleted following Rasch analysis. The final 11-item OAKS was unidimensional. Item functioning was not affected by gender, age, educational level, or scale version (hip or knee). Person separation index was 0.75. Test-retest intraclass correlation coefficient was 0.81 (95% CI 0.74, 0.86; hip version 0.66 [0.47, 0.79]; knee version 0.85 (0.79, 0.90)). Smallest detectable change was 9 points (scale range 11–55; hip OA version 11 points; knee OA version 8 points).

Conclusion

The OAKS is a psychometrically adequate, unidimensional measure of important OA knowledge that can be used in populations with and without hip and knee OA. Caution is needed when using with populations with only hip OA as test-retest reliability of the hip version did not surpass the acceptable range.     

Muscle strength, endurance, and aerobic capacity in rheumatoid arthritis: a comparative study with healthy subjects.

Isometric/isokinetic muscle strength and isokinetic endurance of the lower extremities as well as aerobic capacity were evaluated in 67 patients (43 female, 24 male; mean age 53 years, range 23-65) with classical/definite rheumatoid arthritis (RA) of functional class II. Results obtained were compared with those of a healthy reference group matched for age and sex. Disease characteristics of the group with RA were registered and lifestyle characteristics, such as work load, exercise, diet, smoking, and alcohol habits, were reported by both groups. Generally, results showed that the group with RA had decreased functional capacity. Isometric hip and knee muscle strength of the rheumatoid group was reduced to about 75% of normal function, isokinetic knee muscle strength at the velocities of 60 and 180 degrees/s to about 65% and 75% of normal function respectively, isokinetic endurance of the knee muscle groups to about 45%, and aerobic capacity to about 80% of the results obtained for the healthy reference group. Analyses of variance showed that the rheumatoid group, compared with the healthy group, had significantly reduced function on all isometric and isokinetic tests of the extensors and flexors of the knee. Results for isometric hip muscle strength were similar--all tests but one yielding highly significant differences. To avoid unnecessary functional deficits it seems important to include muscular training in rehabilitation programmes for patients with RA.     

Association of the interleukin‐1 gene cluster on chromosome 2q13 with knee osteoarthritis

Objective

To investigate whether the interleukin‐1 (IL‐1) ligand gene cluster at 2q13 encodes for genetic susceptibility to primary osteoarthritis (OA).

Methods

Seven single‐nucleotide polymorphisms (SNPs) and a variable‐number tandem repeat (VNTR) polymorphism from within the IL‐1 ligand genes IL1A, IL1B, and IL1RN were genotyped in a cohort of 557 OA cases and 557 age‐matched controls.

Results

None of the variants demonstrated association in the unstratified data set. However, when cases were stratified according to sex and site of disease (hip or knee), 4 SNPs showed marginal evidence for association (P < 0.1) in knee cases (n = 136) and male knee cases (n = 58). For 2 of these SNPs, evidence for association was enhanced when probands from 60 knee‐only affected sibling pair families were genotyped and combined with the original knee cases (P ≤ 0.05). Further analysis revealed that the associated alleles at 2 of these SNPs were markers for the same haplotype, the frequency of which was significantly elevated when knee cases and knee probands were combined (P = 0.01, odds ratio [OR] 1.4) and when male knee cases and male knee probands were combined (P = 0.009, OR 1.7). Furthermore, linkage analysis of 2q revealed suggestive evidence for linkage to the IL‐1 gene clusters in affected sibling pairs concordant for knee OA but no evidence for linkage in affected sibling pairs concordant for hip OA.

Conclusion

The IL‐1 ligand cluster encodes for susceptibility to knee OA but not to hip OA, highlighting the genetic heterogeneity of this common, complex disease.