OA is a painful joint disease that predominantly affects the elderly. Pain is the primary symptom of OA, and it can present as either intermittent or constant. OA pain mechanisms are complex and have only recently been determined. Both peripheral and central processes are involved in creating the OA pain experience, making targeted therapy problematic. Nociceptive, inflammatory and neuropathic pains are all known to occur in OA, but to varying degrees in a patient- and time-specific manner. A better understanding of these multifactorial components of OA pain will lead to the development of more effective and safer pain treatments.

Background Thumb-base osteoarthritis (OA) is a common cause of pain and disability This study aimed to investigate the associations of musculoskeletal ultrasound OA pathologies with the extent of pain, function, radiographic scores, and muscle strength in symptomatic thumb-base osteoarthritis. Methods This is a cross-sectional study of an ongoing clinical trial with eligibility criteria including thumb-base pain on Visual Analogue Scale (VAS) ≥40 (0 to 100 mm), Functional Index for Hand OA (FIHOA) ≥ 6 (0 to 30) and Kellgren Lawrence (KL) grade ≥ 2. The most symptomatic side was scanned to measure synovitis and osteophyte severity using a 0–3 semi-quantitative score, power Doppler and erosion in binary score. A linear regression model was used for associations of ultrasound findings with VAS pain, FIHOA and hand grip and pinch strength tests after adjusting for age, gender, body mass index, disease duration and KL grade as appropriate. For correlation of ultrasound features with KL grade, OARSI ((Osteoarthritis Research Society International) osteophyte and JSN scores, Eaton grades, Spearman coefficients were calculated, and a significant test defined as a p -value less than 0.05. Results The study included 93 participants (mean age of 67.04 years, 78.5% females). Presence of power Doppler has a significant association with VAS pain [adjusted β coefficient = 11.29, P = 0.02] while other ultrasound pathologies revealed no significant associations with all clinical outcomes. In comparison to radiograph, ultrasonographic osteophyte score was significantly associated with KL grade [r s = 0.44 ( P < 0.001)], OARSI osteophyte grade [r s = 0.35 ( P = 0.001)], OARSI JSN grade [r s = 0.43 (P < 0.001)] and Eaton grade [r s = 0.30 ( P < 0.01)]. Ultrasonographic erosion was significantly related with radiographic erosion [r s = − 0.49 (P = 0.001)]. Conclusion From a clinical perspective the significant relationship of power Doppler with pain severity in thumb base OA suggests this might be a useful tool in understanding pain aetiology. It is important to recognise that power Doppler activity was only detected in 14% of the study so this might be an important subgroup of persons to monitor more closely. Trial registration Registered at Australian New Zealand Clinical Trials Registry (ANZCTR), http://www.anzctr.org.au/ , ACTRN12616000353493.

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