Objectives-To investigate whether subjects with knee osteoarthritis (OA) have reduced static postural control, knee proprioceptive acuity, and maximal voluntary contraction (MVC) of the quadriceps compared with normal controls, and to determine possible independent predictors of static postural sway. Methods-77 subjects with symptomatic and radiographic knee OA (58 women, 19 men; mean age 63.4 years, range 36-82) and 63 controls with asymptomatic and clinically normal knees (45 women, 18 men; mean age 63 years, range 46-85) underwent assessment of static postural sway. 108 subjects (59 patients, 49 controls) also underwent assessment of knee proprioceptive activity and MVC (including calculation of quadriceps activation). In patients with knee OA knee pain, stiVness, and functional disability were assessed using the WOMAC Index. The height (m) and weight (kg) of all subjects was assessed. Results-Compared with controls, patients with knee OA were heavier (mean diVerence 15.3 kg, p<0.001), had increased postural lateral sway (controls: median 2.3, interquartile (IQ) range 1.8-2.9; patients: median 4.7, IQ range 1.9-4.7, p<0.001), reduced proprioceptive acuity (controls: mean 7.9, 95% CI 6.9 to 8.9; patients: mean 12.0, 95% CI 10.5 to 13.6, p<0.001), weaker quadriceps strength (controls: mean 22.5, 95% CI 19.9 to 24.6; patients: mean 14.7, 95% CI 12.5 to 16.9, p<0.001), and less percentage activation of quadriceps (controls: mean 87.4, 95% CI 80.7 to 94.2; patients: mean 66.0, 95% CI 58.8 to 73.2, p<0.001). The significant predictors of postural sway were knee pain and the ratio of MVC/body weight. Conclusions-Compared with age and sex matched controls, subjects with symptomatic knee OA have quadriceps weakness, reduced knee proprioception, and increased postural sway. Pain and muscle strength may particularly influence postural sway. The interaction between physiological, structural, and functional abnormalities in knee OA deserves further study. (Ann Rheum Dis 2001;60:612-618) Control of balance is vital to everyday life. It allows performance of activities that range from maintenance of static positions to complex dynamic activities. Postural control is complex and on the aVerent side involves the central processing of peripheral sensory input from vestibular, visual, and proprioceptive pathways, whereas the eVerent side involves the precise recruitment of specific (and varying) populations of motor units. Peripheral proprioception involves various sensory receptors, including cutaneous touch and pressure receptors, mechanoreceptors of synovial joints, muscle spindles, and tendon Golgi organs. Muscle spindles are the more important for detecting changes in joint angulation in the mid-range of movement, whereas joint mechanoreceptors (pacinian corpuscles and RuYni's end organs), which detect stretch of ligaments and deep tissues, are more important at the extremes of joint movement. The knee joint has a rich sensory innervation and has mechanoreceptors in the anterior and posterior cruciate ligaments,...

Objective: To investigate whether alleviation of knee pain influences quadriceps function, proprioceptive acuity, and postural stability in patients with knee osteoarthritis (OA). Methods: A crossover, within-subject, double blind study design involving 68 subjects with painful knee OA. Each subject received an intra-articular injection into one or both knees (both if symptomatic) of either 5 ml 0.5% bupivacaine or 5 ml 0.9% saline. Two weeks later they received an injection of the alternative agent. Subjects and observer were unaware of the order of injection, which was randomly assigned. Knee pain (100 mm visual analogue scale), static postural sway, knee proprioceptive acuity, maximum voluntary contraction (MVC), and percentage activation of the quadriceps were assessed immediately before and one hour after each injection. Results: Significant pain reduction was achieved one hour post-bupivacaine (mean difference as a percentage change 56.85, 95% CI 31.01 to 73.65; p<0.001) and post-saline (mean difference as a percentage change 41.94, 95% CI 11.57 to 76.66; p< 0.001), with no significant difference between the two. Both MVC and activation increased significantly post-bupivacaine (mean percentage differences 18.83, 95% CI −31.79 to −0.26, and −11.90, 95% CI −39.53 to 2.97, respectively; both p<0.001) and post-saline (mean percentage differences −7.64, 95% CI −21.96 to 4.73, and −10.71, 95% CI −25.19 to 2.60 respectively; both p<0.001). Proprioception worsened after bupivacaine (mean percentage difference −28.15%, 95% CI −83.47 to 19.74; p=0.009), but there was no effect on postural sway; saline injection had no effects. There was no order effect, and comparison of median percentage changes showed no significant differences between injections for change in MVC, activation, proprioception, or sway. Conclusion: Reduction in knee pain through either peripheral (local anaesthetic) or central (placebo) mechanisms resulted in increased MVC. This increase, however, did not result in improvements in proprioception or static postural stability, suggesting that other mechanisms play a part in these functions, at least in this acute model.

Objectives-To (a) develop an atlas of line drawings for the assessment and grading of narrowing and osteophyte (that is, changes of osteoarthritis) on knee radiographs, and (b) compare the performance of this atlas with that of the standard Osteoarthritis Research Society (OARS) photographic atlas of radiographs. Methods-Normal joint space widths (grade 0) for the medial and lateral tibiofemoral and medial and lateral patellofemoral compartments were obtained from a previous community study. Grades 1-3 narrowing in each compartment was calculated separately for men and women, grade 3 being bone on bone, grades 1 and 2 being two thirds and one third the value of grade 0. Maximum osteophyte size (grade 3) for each of eight sites was determined from 715 bilateral knee x ray films obtained in a knee osteoarthritis (OA) hospital clinic; grades 1-2 were calculated as two thirds and one third reductions in the area of grade 3. Drawings for narrowing and osteophyte were presented separately. 50 sets of bilateral knee x ray radiographs (standing, extended anteroposterior; flexed skyline) showing a spectrum of OA grades were scored by three observers, twice using the OARS atlas and twice using the drawn atlas. Results-Intraobserver and interobserver reproducibility was similar and generally good with both atlases, though varied according to site. All three observers preferred the line drawing atlas for ease and convenience of use. Higher scores for patellofemoral narrowing and lower scores for osteophyte, especially medial femoral osteophyte, were seen using the line drawing atlas, showing that the two atlases are not equivalent instruments. Conclusion-A logically derived line drawing atlas for grading of narrowing and osteophyte at the knee has been produced. The atlas showed comparable reproducibility with the OARS atlas, but was discordant in several aspects of grading. Such a system has several theoretical and practical advantages and should be considered for use in knee OA studies.