The lack of strong association between knee osteoarthritis (OA) structural features and pain continues to perplex researchers and clinicians. Evaluating the patellofemoral joint in addition to the tibiofemoral joint alone has contributed to explaining this structure-pain discordance, hence justifying a more comprehensive evaluation of whole-knee OA and pain. We therefore evaluated the association between patellofemoral and tibiofemoral OA features with localized anterior knee pain (AKP) using two study designs.
Using cross-sectional data from the Multicenter Osteoarthritis Study, our first approach was a within-person, knee-matched design in which we identified participants with unilateral AKP. We then assessed MRI-derived OA features (cartilage damage, bone marrow lesions [BMLs], osteophytes, and inflammation) in both knees, and evaluated the association of patellofemoral and tibiofemoral OA features to unilateral AKP. In our second approach, MRIs from one knee per person were scored, and we evaluated the association of OA-features to AKP in participants with AKP and participants with no frequent knee pain.
Using the first approach (n=71, 66% women, mean age 69 [SD 8] years), lateral patellofemoral osteophytes (odds ratio 5.0 [95% CI 1.7, 14.6]), whole-knee joint effusion-synovitis (4.7 [1.3, 16.2]), and infrapatellar synovitis (2.8 [1.0, 7.8]) were associated with AKP. Using the second approach (n=882, 59% women, mean age 69 [SD 7] years), lateral and medial patellofemoral cartilage damage (prevalence ratio 2.3 [1.3, 4.0] and 1.9 [1.1, 3.3]), and lateral patellofemoral BMLs (2.6 [1.5, 4.7]) were associated with AKP.
Patellofemoral but not tibiofemoral joint OA features, and inflammation were associated with AKP.