Return to play following muscle injuries in professional footballers.

This prospective cohort study described return-to-play (RTP) data for different types of muscle injuries in male elite-level football players in Europe. Eighty-nine European professional teams were followed between 2001 and 2013. Team medical staff recorded individual player exposure and time-loss injuries. A total of 17,371 injuries occurred, including 5603 (32%) muscle injuries. From 2007, we received results from 386 magnetic resonance imaging (MRI) examinations, and radiological grading was performed. A negative MRI was associated with shorter recovery time (6 ± 7 days). Lay-off days were correlated with MRI grading of thigh muscle injuries (P < 0.001). Among hamstring injuries, 83% occurred to the biceps femoris, 12% affected the semimembranosus and 5% the semitendinosus. Recurrence rate was higher among biceps femoris injuries (18%) compared with semitendinosus and semimembranosus injuries (2% together). Groin muscle injuries caused shorter median absence (9 days) than hamstring (13 days; P < 0.001), quadriceps (12 days; P < 0.001) and calf muscle (13 days; P < 0.001) injuries. Overall, we found that MRI was valuable for prognosticating RTP, with radiological grading associated with lay-off times after injury. Re-injuries were common in biceps femoris injuries but rare in semitendinosus and semimembranosus injuries.