No Obvious Association
The article (1) spells doom for football, and perhaps other sports during adolescence: football causes genu varum (bowlegs), and bowlegs in adolescents turns into knee osteoarthritis in adults. Only: this is not supported by the data, and neither is there any evidence for the consequences. The meta-analysis included case–control studies, which without longitudinal studies are not suitable for establishing causalities (in this case: between football and bowlegs).
The association between bowlegs and later knee osteoarthritis is not obvious. In the cited review by Tanamas et al. (2), only 1 of 14 included studies found an increased risk for the development of knee osteoarthritis as a result of leg malalignment, and only in overweight persons. Other longitudinal studies—for example, that reported by Hunter et al. (3)—did not find any increase in risk.
The orthopedic myth, that bowlegs and genu valgum deformity (“knock-knees”) lead to knee osteoarthritis, results from the ex post view—namely, the pronounced malalignment of the leg axis in knee osteoarthritis. The conclusion: bowlegs and knock-knees don’t cause knee osteoarthritis, but knee osteoarthritis causes bowlegs and knock-knees.
An intercondylar distance of more than 1.5 cm in young people who play football should not be construed into a drama. Cruciate ligament injury and especially cartilage loss—whether as a result of traumatic injury or iatrogenic—advance knee osteoarthritis substantially. And: in addition to age, overweight and obesity also have a confirmed effect in terms of advancing knee osteoarthritis (4).
Prof. Dr. med. Marcus Schiltenwolf
Zentrum für Orthopädie, Unfallchirurgie und Paraplegiologie,
|1.||Thaller PH, Fürmetz J, Chen F, Degen N, Manz KM, Wolf F: Bowlegs and intensive football training in children and adolescents—a systematic review and meta-analysis. Dtsch Arztebl Int 2018; 115: 401–8 VOLLTEXT|
|2.||Tanamas S, Hanna FS, Cicuttini FM, Wluka AE, Berry P, Urquhart DM: Does knee malalignment increase the risk of development and progression of knee osteoarthritis? A systematic review. Arthritis Rheum 2009; 61: 459–67 CrossRef MEDLINE|
|3.||Hunter DJ, Niu J, Felson DT, et al.: Knee alignment does not predict incident osteoarthritis: the Framingham osteoarthritis study. Arthritis Rheum 2007; 56: 1212–8 CrossRef MEDLINE|
|4.||Schiltenwolf M, Liebers F, Bolm-Audorff U, et al.: Welche konkurrierenden Faktoren sind bei der Begutachtung der Gonarthrose zu berücksichtigen? In: Schiltenwolf M, Grosser V, Thomann KD (eds.): Berufskrankheit Gonarhtorse (BK 2112). Frankfurt am Main: Referenz Verlag 2012.|