Table 1

Eligibility criteria

Dutch cohortQatar cohort
Inclusion criteria

  • Age 18–50 years

  • Clinical diagnosis of acute hamstring injury

  • Presenting and MRI within 5 days from injury

  • MRI confirmed grades I or II hamstring lesion

  • Second MRI available within 3 days of RTP

  • Age 18–50 years

  • Acute onset of posterior thigh pain

  • Presenting and MRI within 5 days from injury

  • MRI confirmed grades I or II hamstring lesion

  • Second MRI available within 3 days of RTP

  • Gender: male

  • Available to perform five sessions physiotherapy a week at the clinic

  • Available for follow-up

Exclusion criteria

  • Contraindication to MRI

  • Chronic hamstring injury

  • Chronic low back pain

  • Cause of injury is an extrinsic trauma

  • Not capable of performing rehabilitation

  • No intention to return to full sports activity

  • Unwilling to receive the intramuscular injections

  • Injection therapy received for this injury before

  • Contraindication to MRI

  • Reinjury or chronic hamstring injury

  • Concurrent other injuries inhibiting rehabilitation

  • Unwilling to comply with follow-up

  • Needle phobia

  • Overlying skin infection

  • Diabetes, immunecompromised state

  • Medication increasing bleeding risk (eg, Plavix)

  • Medical contraindication to injection

  • RTP, return to play.