How do pain and function vary with compartmental distribution and severity of radiographic knee osteoarthritis?

Objectives. In radiographic OA (ROA) of the knee, how does radiographic severity and pattern of compartmental involvement influence symptoms? Methods. Population-based study of 819 adults aged >= 50 yrs with knee pain. The severity of knee pain and function were measured using the Western Ontario and McMaster Universities scale. Three radiographic views of the knees were obtained. Results. Seven hundred and seventy-seven participants were eligible (mean age 65.5 yrs, 357 males). Higher ROA severity in each of the tibiofemoral (TF) and patellofemoral (PF) compartments was independently associated with higher mean pain scores (TF: F-2,F- 700 = 9.0, P < 0.0001, PF: F-2,F- 700 = 12.7, P < 0.0001). The same pattern was found for mean function scores (TF: F-2,F- 705 = 7.1, P = 0.001, PF: F-2,F- 705 = 15.9, P < 0.0001). If either the TF or PF compartment was affected by moderate/severe OA, the added presence of OA in the other compartment did not increase the mean pain or function scores. Conclusions. It is the severity of radiographic disease within a compartment, rather than the distribution of radiographic disease between compartments that is associated with symptoms. ROA in the PF joint is associated with symptoms, emphasizing the importance of radiographic changes in his joint.