Risk factors of recurrent hamstring injuries: a systematic review

Background Although recurrent hamstring injury is a frequent problem with a significant impact on athletes, data on factors determining the risk for a recurrent hamstring injury are scarce. Objective To systematically review the literature and provide an overview of risk factors for re-injury of acute hamstring muscle injuries. Study design Prospective studies on risk factors for re-injury following acute hamstring injuries were systematically reviewed. Medical databases and reference lists of the included articles were searched. Two reviewers independently selected potential studies and assessed methodological quality; one reviewer extracted the data. A best-evidence synthesis of all studied risk factors was performed. Results Of the 131 articles identified, five prospective follow-up studies fulfilled our inclusion criteria. These studies reported a recurrence incidence of 13.9-63.3% in the same playing season up to 2 years after initial injury. Limited evidence for three risk factors and one protective factor for recurrent hamstring injury was found; patients with a recurrent hamstring injury had an initial injury with a larger volume size as measured on MRI (47.03 vs 12.42 cm(3)), more often had a Grade 1 i Conclusions There is limited evidence that athletes with a larger volume size of initial trauma, a Grade 1 hamstring injury and a previous ipsilateral ACL reconstruction are at increased risk for recurrent hamstring injury. Athletes seem to be at lower risk for re-injury when following agility/stabilisation exercises