The contribution of selected non-articular conditions to knee pain severity and associated disability in older adults.

OBJECTIVE: To estimate the contribution of selected non-articular conditions (NACs) to pain severity and functional limitation in community-dwelling older adults with knee pain. DESIGN: Population-based, cross-sectional study of 745 adults aged 50 years and over with knee pain. Self-complete questionnaires, clinical history and physical examination were used to identify the presence of selected NACs that could cause pain around the knee. Regression analyses were used to compare levels of knee pain severity (0-20) and functional limitation (0-68) (Western Ontario and McMaster Universities osteoarthritis index physical function subscale [WOMAC-PF]), between those with one or more NACs and those with none (NACs-absent). RESULTS: Two hundred and seventy-three (36.6%) participants had at least one NAC: widespread pain, n=159; low back pain with index leg referral, n=102; full-leg pain, n=88; hip arthritis, n=65; prepatellar, infrapatellar or pes anserine bursitis, n=35. The NACs group had significantly higher levels of pain severity and functional limitation than the NACs-absent group: 8.2(+/-4.6) vs 5.4(+/-3.8) and 27.9(+/-15.8) vs 16.8(+/-13.2), respectively. The groups did not differ with respect to severity of radiographic osteoarthritis (ROA). Having one or more NACs accounted for a significant proportion of the variance in WOMAC scores, above that which could be explained by age, gender, body mass index and severity of ROA. CONCLUSION: NACs appear to be common in older adults with knee pain. They make a significant contribution to knee pain severity and functional limitation and are likely to represent additional, rather than alternative, causes of knee pain/functional limitation to osteoarthritis (OA). These factors should be taken into account in epidemiological studies of knee pain and OA.

Knee osteoarthritis in community-dwelling older adults: are there characteristic patterns of pain location?

OBJECTIVE: To determine whether there are characteristic patterns of pain location associated with knee osteoarthritis (OA) among community-dwelling older adults. DESIGN: Population-based, cross-sectional survey of 697 adults aged 50 years and over reporting knee pain within the past 6 months. Pain at 13 individual sites at or around the knee was coded. Pain locations in participants with and without "symptomatic knee OA" (defined as symptoms on most days in the past month, at least a definite osteophyte on plain X-ray, and current pain intensity of at least 2 out of 10) were compared. Participants were then grouped by pattern of knee pain location, and their clinical and radiographic characteristics compared. RESULTS: Generalised knee pain (n=313) and medial knee pain (either in isolation or with peripatellar or lateral knee pain: n=175) were the most common patterns. Medial knee pain and distally radiating pain were significantly more likely in those with symptomatic knee OA. Individuals with generalised knee pain with radiation had more persistent, severe pain, and a relatively high proportion had moderate or severe radiographic disease. CONCLUSION: No single pattern of pain location is pathognomonic for knee OA. Attention towards the role of peripheral nociception and central sensitisation in producing medial knee pain and distally radiating knee pain is warranted.