Table 1.

Eligibility criteria

Dutch cohort	Qatar 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.