Participation in some sports, not running, increases risk of knee and hip osteoarthritis

The rates of reduction of hip replacement (an end-stage treatment of hip OA) were 35.1%, 50.4%, and 38.5%, respectively. These data, combined with the body mass index (BMI) data of the runners, suggest that running reduced OA and hip replacement risk partially due to the lower BMI associated with runners. Furthermore, the study showed that increased running speed, distance, or years of running did not increase OA risk, but seemed to increase risk of hip replacement. The results also demonstrated that running presents no increased risk for OA compared to walking. The author argued that running may decrease OA more than walking due to the larger percentage of runners (89.5%) who exceeded 1.8 MET-h/day compared to walkers (52.8%). However, the study did not report jointspecific OA in the runners. This prospective cohort study has a large sample size, exceeding the number of surveyed runners 10 times compared to the number of runners surveyed in all previous cross-sectional running studies combined. 3 OA risks associated with participation in other vigorous sports are not clearly evidenced and consistent in the literature. A recent systematic review and meta-analysis on the effects of sport activities on OA predictions (hip, knee, and ankle) provide some new insight. 4 The review, which initially identified 1294 studies and included 43 qualified studies according to a pre-defined set of criteria, included studies that had a large variation in the number of participants (16e8000) and duration of the study period (30 monthse40 years). Regarding the relationship between OA and sport activity, 12 papers met the inclusion criteria, including two retrospective cohort studies, two case series studies, seven caseecontrol studies, and one cross-sectional study. Either radiographic or magnetic resonance imaging was used to define OA in most of the studies; questionnaire, physician diagnosis, and selfreported pain and disability were also used in some of the studies. It was reported that participation in team sports was a risk factor for knee OA onset prior to 45 years of age. 5 One study identified participation in soccer as a risk factor for knee OA 6 while another study did not identify it as a risk factor. 7 Females had an increased risk of developing knee OA compared to males when participating in gymnastics or Kung Fu. 8 A caseecontrol study showed that an increased risk of developing knee OA was associated with participation in soccer, ice hockey, and tennis, but not in track and field, skiing, and orienteering. 9 However, after adjustment for knee