Tibial genu varum and primary cam morphology in healthy young adults: A cross-sectional study uncovering the double threat to joint health

Objectives: This study investigated the association between alpha angles of the hip and tibial genu varum in a healthy population with equal male-to-female distribution. It also examined sex-based differences, explored the impact of sports participation, and assessed the interplay between these conditions. Methods: Tibial, femoral, intra-articular knee deformities, and the alpha angle of the hip were analysed in 200 healthy volunteers (400 legs) aged 20–27 years using weight-bearing radiographs. The Tegner score was retrospectively collected and used to distinguish between high and low sports activity. Generalized estimating equations were used to examine the association between lower limb malalignment and alpha angle, accounting for side and gender. Results: Tibial alignment was associated with the alpha angle (β = −0.02, P = 0.002); tibial genu varum was associated with a higher alpha angle. Other deformities and their interaction with sports activity had no association with the alpha angle. Males exhibited a higher alpha angle (β = 0.19, P < 0.001, Δ = 9.0°) and more tibial genu varum (β = −0.95, P = 0.002, Δ = 1.1°) than females. High sports activity was associated with increased tibial genu varum (β = −0.75, P = 0.02) compared to low sports activity. Conclusion: This study found a significant association between alpha angle and tibial genu varum. Males exhibited higher alpha angles and more tibial genu varum than females. While higher sports activity was associated with tibial genu varum, no differences in alpha angle were seen across activity levels. These findings urge for future research to further explore mechanical load adjustments that prevent genu varum and primary cam morphology, reducing osteoarthritis risk.