The association of frontal plane alignment to MRI-defined worsening of patellofemoral osteoarthritis: the MOST study

Objective:To determine the sex-specific relation of frontal plane alignment (FPA) to magnetic resonanceimaging (MRI)-defined features of patellofemoral osteoarthritis, and also to tibiofemoral osteoarthritisand knee pain.Method:The Multicenter Osteoarthritis Study is cohort study comprised of individuals with or at risk ofknee osteoarthritis. We determined the sex-specific doseeresponse relation of baseline FPA to MRI-defined patellofemoral and tibiofemoral structural worsening, and incident knee pain, over 7 years.Results:In women only, greater varus alignment was associated with medial patellofemoral osteophytes(risk ratio [RR] 1.7 [95% CI 1.2, 2.6]) and valgus with lateral patellofemoral osteophytes (RR 1.9 [1.0, 3.6]).In men, greater varus increased risk for medial tibiofemoral cartilage worsening (RR 1.7 [1.1, 2.6]), andvalgus for lateral tibiofemoral cartilage worsening (RR 1.8 [1.6, 2.2]). In women,findings were similar fortibiofemoral cartilage, but varus also increased risk for medial bone marrow lesions [BMLs] (RR 2.2 [1.6,3.1]) and medial osteophytes (RR 1.8 [1.3, 2.5]), and valgus for lateral BMLs (RR 3.3 [2.2, 4.5]) andosteophytes (RR 2.0 [1.2, 3.2]). Varus increased risk of incident pain in men (RR 1.7 [1.4, 2.2]) and women(RR 1.3 [1.0, 1.6]), valgus did so in men only (RR 1.5 [1.1, 1.9]).Conclusion:FPA was associated with patellofemoral osteophyte worsening in women, though overall wasmore strongly associated with tibiofemoral than patellofemoral osteoarthritis feature worsening. FPA inwomen was more consistently associated with structural worsening, yet men had higher associationswith incident pain.

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