The association of knee structural pathology with pain at the knee is modified by pain at other sites in those with knee osteoarthritis.

The objective of this study was to investigate the associations of knee structural abnormalities with different patterns of pain. A total of 891 participants (average age 63 years; range 50 to 80 years) participated in this study. Presence of pain at the neck, back, hands, shoulders, hips, knees, and feet was assessed by questionnaire. Participants were categorized as having no pain at any site (no pain), pain only at the knee (KP), pain at other sites but not the knee (OP), and pain at the knee and other sites (KOP). T1-weighted or T2-weighted MRI of the right knee was performed to measure cartilage defects, bone marrow lesions (BMLs), and effusion-synovitis. Osteophytes and joint space narrowing were assessed by X-ray. KP, KOP, and OP were, respectively, present in 3, 43, and 42% of the participants. In multivariable analyses, KOP was associated with the presence of cartilage defects, BMLs, and osteophytes (OR 3.57 (95% CI 1.78 to 7.14), 2.37 (1.27 to 4.43), and 2.87 (1.10 to 7.51), respectively) in those with radiographic knee OA. KP was also associated with presence of these structural abnormalities as well as effusion-synovitis, and these associations were much stronger. The associations between structural abnormalities and KOP were weaker than those with KP in those with radiographic knee OA. This suggests that mechanisms mediating the association between structural pathology, localized, and generalized pain may be different, and central sensitization is possibly involved in generalized pain. Pain at other sites needs to be considered in the management and treatment of OA-related pain.