Valgus bracing can relocate cartilage contact pressure away from bone marrow lesions and full-thickness cartilage defects in varus-malaligned medial knee osteoarthritis

Objective: To examine whether valgus bracing reduces cartilage contact pressure atop structural sources of weight-bearing pain in varus-malaligned medial knee osteoarthritis. Design: An exploratory secondary analysis of a within-participant longitudinal study involving an 8-week valgus brace intervention. Methods: Baseline biomechanical data and 8-week change scores in the KOOS pain subscale from participants with ≥1 bone marrow lesion (BML) on the medial tibia were analysed (n = 21). Magnetic resonance imaging (MRI) assessed medial tibial BMLs and full-thickness cartilage defects. A 12 degree-of-freedom MRI-informed knee neuromusculoskeletal model quantified cartilage pressure exerted atop BMLs and cartilage defects. Peak pressure magnitude (MPa) atop BMLs and defects was compared between braced and unbraced walking using paired t-tests. Responder rate (did/did not reduce pressure atop BMLs/defects, and ≥MCID KOOS pain) was examined using Fisher's exact test. Results: Cartilage contact pressure was exerted atop BML(s) during unbraced walking for 15 of 21 (71%) participants; and in 9 of 11 (82%) participants who had cartilage defects. Braced walking reduced peak magnitude pressure atop BMLs by 13% (-1.2 MPa [95%CI -2.0, -0.4], p = 0.008) and defects by 18% (-1.9 MPa [95%CI -3.3, -0.5], p = 0.013). Participants who reduced peak pressure atop a BML and/or cartilage defect were more likely to exceed the KOOS MCID than those who did not (risk difference: 60 percentage points [95%CI 17, 84], p = 0.011). Conclusions: Valgus bracing reduced cartilage contact pressure atop BMLs and defects among those who loaded these lesions. This biomechanical response was associated with a pain improvement, a hypothesis-generating finding that warrants further examination.