Objective: To systematically summarize the literature on the course of pain in patients with knee osteoarthritis (OA), prognostic factors that predict deterioration of pain, the course of physical functioning, and prognostic factors that predict deterioration of physical functioning in persons with knee OA.Methods: A search was conducted in PubMed, CINAHL, Embase, Psych‐INFO, and SPORTDiscus up to January 2014. A meta‐analysis and a qualitative data synthesis were performed.Results: Of the 58 studies included, 39 were of high quality. High heterogeneity across studies (I² >90%) and within study populations (reflected by large SDs of change scores) was found. Therefore, the course of pain and physical functioning was interpreted to be indistinct. We found strong evidence for a number of prognostic factors predicting deterioration in pain (e.g., higher knee pain at baseline, bilateral knee symptoms, and depressive symptoms). We also found strong evidence for a number of prognostic factors predicting deterioration in physical functioning (e.g., worsening in radiographic OA, worsening of knee pain, lower knee extension muscle strength, lower walking speed, and higher comorbidity count).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. These findings support current research efforts to define subgroups or phenotypes within knee OA populations. Strong evidence was found for knee characteristics, clinical factors, and psychosocial factors as prognostics of deterioration of pain and physical functioning.

Objectives Knee osteoarthritis (OA) is a leading cause of activity limitations. The knee OA population is likely to consist of subgroups. The aim of the present study was to identify homogeneous subgroups with distinct trajectories of activity limitations in patients with early symptomatic knee OA and to describe characteristics of these subgroups. Methods Follow-up data over a period of 5 years of 697 participants with early symptomatic knee OA from the Cohort Hip and Cohort Knee (CHECK) were used. Activity limitations were measured yearly with the Western Ontario and McMaster Universities Osteoarthritis Index. Latent class growth analyses identified homogeneous subgroups with distinct trajectories of activity limitations. Multivariable regression analyses examined differences in characteristics between the subgroups. Results Three subgroups were identified. Participants in Subgroup 1 (‘good outcome’; n=330) developed or displayed slight activity limitations over time. Participants in Subgroup 2 (‘moderate outcome’; n=257) developed or displayed moderate activity limitations over time. Participants in subgroup 3 (‘poor outcome’; n=110) developed or displayed severe activity limitations over time. Compared with the ‘good outcome’ subgroup, the ‘moderate outcome’ and ‘poor outcome’ subgroups were characterised by: younger age, higher body mass index, greater pain, bony tenderness, reduced knee flexion, hip pain, osteophytosis, ≥3 comorbidities, lower vitality or avoidance of activities. Conclusions Based on the 5-year course of activity limitations, we identified homogeneous subgroups of knee OA patients with good, moderate or poor outcome. Characteristics of these subgroups were consistent with existing knowledge on prognostic factors regarding activity limitations, which supports the validity of this classification.

Objective: To examine the diagnostic accuracy of hip internal rotation, hip flexion, and knee flexion measurements for the presence of osteophytosis and joint space narrowing (JSN) in early symptomatic osteoarthritis (OA).Methods: The baseline data for 598 participants of the Cohort Hip & Cohort Knee study were used. Participants underwent a standardized physical and radiographic examination. The active range of motion (ROM) was assessed using a goniometer. The ROM cutoff with the highest discriminative ability for radiographic features of OA was defined by maximizing the sum of the sensitivity and specificity. Several diagnostic measures were calculated to establish the diagnostic accuracy of ROM measurements for the presence of radiographic features.Results: In patients with hip symptoms, hip internal rotation <24° and flexion <114° were found to be the cutoffs with the highest discriminative ability to distinguish between patients with and without radiographic features. In patients with knee symptoms, knee flexion <132° was the cutoff with the highest discriminative ability. The American College of Rheumatology (ACR) criterion of hip internal rotation <15° increased the probability of the presence of osteophytosis or JSN from 25% to 58%. The diagnostic accuracy of hip and knee flexion measurements was low.Conclusion: To reduce the number of patients that are not identified by the ACR criterion of hip internal rotation <15°, it is recommended to change the cutoff to internal rotation <24° in patients with early symptomatic OA. Individual hip and knee flexion measurements seem to be of little diagnostic value in early symptomatic OA.