Introduction Hamstring injury is the most common injury in professional football¹ MRI is often used as both a diagnostic and prognostic tool, but clinical judgment is always used to assess injury. There is little evidence in current literature to compare the two.

Aims To evaluate MRI scanning for predicting time missed after hamstring injuries and compare it to clinical judgment.

Methods A retrospective study was carried out, using the medical database of Sunderland AFC (SAFC): a Premier League football club. Players with a hamstring injury who had had an MRI scan were selected. Injuries occurred between 7/03/2009 and 16/02/2013. I found 'individual time-loss', 'radiological findings on MRI' and ‘clinical findings’ for each player's injury, in documentation by medical staff at SAFC. MRI findings were interpreted using a modified Peetron's classification into four grades. An established system by Jan Ekstrand² predicts time, in days, out of full contact training and playing football matches, based on Peetron's grades. I used this to analyse the accuracy of MRI and of clinical grading.

Results In total, 27 players had hamstring injuries, all receiving an MRI scan and clinical assessment. For MRI classification, 7.4% were grade 0 injuries, 55.5% grade 1, 37.0% grade 2 and 0% grade 3. Clinical judgment assessed 3.7% at grade 0, 62.9% grade 1, 25.9% grade 2 and 7.4% grade 3. Therefore, clinical grading given by medical professionals did not always concur with grading reported from MRI. When using Erkstrand's grading system, clinical grading was more accurate in predicting time out. MRI grading appeared to underestimate injuries; injuries assessed as low grade in fact led to more days injured than predicted. Most injuries (18/27) were given the same MRI and clinical grading, illustrating that there was only some variation between methods.

Conclusions

1. MRI is helpful in verifying the diagnosis and prognosis of a hamstring injury.

2. Clinical grading appeared more accurate than MRI grading in predicting number of days injured. However, this was not statistically significant (p value 0.25).

3. MRI “under grading” may result in a tendency to encourage players to train too soon.

4. Over 60% of hamstring injuries were of radiological grade 0 or 1 (no signs of fibre disruption on MRI) but, in fact, these injuries caused the majority of days out.