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Objective: To systematically summarize the literature on: (i) the course of pain and physical functioning; and (ii) predictors of deterioration of pain and physical functioning in patients with osteoarthritis of the hip., Methods: A literature search was conducted in PubMed, CINAHL, Embase, PsychINFO and SPORTDiscus up to July 2015. Meta-analyses and qualitative data syntheses were performed., Results: Eleven of the 15 included studies were of high quality. With regard to the course of pain and physical functioning, high heterogeneity was found across studies (I² > 71%) and within study populations (reflected by large standard deviations (SDs) of change scores). Therefore, the course of pain and physical functioning was interpreted to be indistinct. Clinical characteristics (higher comorbidity count and presence of knee osteoarthritis), health behaviour factors (no supervised exercise and physical inactivity) and socio-demographics (lower education) were found to predict deterioration of pain (weak evidence). Higher comorbidity count and lower vitality were found to predict deterioration of physical functioning (strong evidence). For several other predictive factors weak evidence was found (e.g. bilateral hip pain, increase in hip pain (change), bilateral knee pain, presence of knee osteoarthritis)., Conclusion: Because of high heterogeneity across studies and within study populations, no conclusions can be drawn with regard to the course of pain and physical functioning. Several clinical characteristics, health behaviours and psychosocial factors prognosticate deterioration of pain and physical functioning. These findings may guide future research aimed at the identification of subgroups of patients with hip osteoarthritis.

Objective: To examine the association between changes in knee muscle strength (extensor and flexor muscles separately, and mean values) and changes in activity limitations in patients with established knee osteoarthritis at 2 years., Methods: Data from 186 patients with knee osteoarthritis, part of the Amsterdam Osteoarthritis cohort, were gathered at baseline and at 2-year follow-up. Strength of the knee extensor and flexor muscles were assessed using an isokinetic dynamometer. Activity limitations were assessed using the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) - Physical Function subscale, the Get Up and Go test (GUG), and the 12-steps stairs test. Univariate and multivariate linear regression analyses were used to assess the association between changes in muscle strength and changes in activity limitations, adjusting for relevant confounders and baseline activity limitations., Results: There was an overall 16% increase in mean knee muscle strength (p < 0.001), 19% increase in knee extensor muscle strength (p < 0.001), and 17% increase in knee flexor muscle strength (p < 0.001) at 2 years. Increased mean knee muscle strength and knee flexor muscle strength were associated with better self-reported physical function (WOMAC) (b = -5.7, p = 0.03 and b = -6.2, p = 0.05), decreased time on the GUG (b = -1.2, p = 0.003 and b = -1.4, p = 0.05) and decreased time on the stairs test (b = -4.4, p < 0.001 and b = -6.6, p < 0.001). Increased extensor muscle strength was associated only with decreased time on the stairs test (b = -2.7, p < 0.001)., Conclusion: Increased knee muscle strength, mainly in the knee flexors, was associated with decreased activity limitations in patients with knee osteoarthritis at 2 years. Thus, differences in muscle strength may partially explain the between-patients variability in activity limitations.

Objective: To determine the association of postural control with muscle strength, proprioception, self-reported knee instability and activity limitations in patients with knee osteoarthritis., Methods: A total of 284 patients with knee osteoarthritis from the Amsterdam Osteoarthritis cohort were included. Postural control was assessed using the One-Leg Stand Test (OLST), in which the patients were asked to stand on one leg for 30 s. Muscle strength (isokinetic dynamometer), proprioception (joint motion detection threshold) and self-reported knee instability (episodes of buckling, shifting or giving way) were also assessed. Activity limitations were assessed using the Get Up and Go (GUG) test, the walking up-down stairs test, and Western Ontario and McMaster University Osteoarthritis Index - Physical Function subscale. Regression analyses were used to assess the associations., Results: Muscle weakness (p = 0.02) and proprioceptive inaccuracy (p < 0.001) were associated with decreased postural control. Decreased postural control was associated with less time performing the GUG test (p < 0.001) and the walking up-down stairs test (p < 0.001). These associations were found after adjustment for relevant confounders., Conclusion: In patients with knee osteoarthritis, decreased postural control is associated with muscle weakness, proprioceptive inaccuracy and performance-based activity limitations. These results highlight the importance of including assessment and training of postural control in this group of patients.