The objective of this study was to investigate the relationship of cartilage loss and bone marrow lesions (BMLs) in the medial and lateral patellofemoral joint (PFJ) to knee pain. The location of full-thickness cartilage loss and BMLs in the PFJ on knee magnetic resonance imaging (MRIs) from the Multicenter Osteoarthritis (MOST) and Framingham Osteoarthritis (FOA) Studies were categorized as no damage, isolated medial, isolated lateral, or both medial and lateral (mixed). The relationship of MRI lesions in each PFJ region to prevalent knee pain were determined. Differences in knee pain severity were compared among categories of PFJ full-thickness cartilage loss and BMLs using quantile regression. In MOST (n=1137 knees), compared with knees without full-thickness cartilage loss, knees with isolated lateral or mixed PFJ full-thickness cartilage loss had 1.9 (1.3, 2.8) and 1.9 (1.2, 2.9) times the odds of knee pain, respectively, while isolated medial cartilage loss had no relationship to knee pain. BMLs in both the medial and lateral PFJ had 1.5 (1.1, 2.0) times the odds of knee pain compared with knees without BMLs. Knee pain severity was lowest in knees with isolated medial PFJ cartilage loss or BMLs. In FOA (n=934 knees), neither isolated medial nor lateral cartilage loss was associated with knee pain, while isolated BMLs in either region were associated with pain.
The results were not completely concordant but indicate that knee pain risk and severity is greatest with cartilage loss isolated to (MOST) or inclusive of (MOST and FOA) the lateral PFJ. While BMLs in either the medial or lateral PFJ are associated with pain.