Baseline patient characteristics and MRI findings
| All participants (n=165) | Qatar cohort (n=90) | Dutch cohort (n=75) | |
| Age (years) | (IQR:22 – 31) | (IQR:22 – 30) | (IQR:22 – 33) |
| Sport | |||
| Football | 119 (72%) | 66 (73%) | 53 (71%) |
| Hockey | 14 (9%) | 2 (2%) | 12 (16%) |
| Futsal | 9 (6%) | 8 (9%) | 1 (1%) |
| Athletics | 5 (3%) | 4 (4%) | 1 (1%) |
| Other | 18 (11%) | 10 (11%) | 8 (11%) |
| Level of participation | |||
| Professional | 87 (53%) | 87 (97%) | 0 (0%) |
| Competitive | 58 (35%) | 3 (3%) | 55 (73%) |
| Recreational | 20 (12%) | 0 (0%) | 20 (27%) |
| Previous (ipsilateral) hamstring injury in the last 12 months | |||
| Yes | 37 (22%) | 11 (12%) | 26 (35%) |
| No | 128 (78%) | 79 (88%) | 49 (65%) |
| MRI grade | |||
| Grade 1 | 68 (41%) | 47 (52%) | 21 (28%) |
| Grade 2 | 97 (59%) | 43 (48%) | 54 (72%) |
| Muscle injured | |||
| Biceps femoris | 135 (82%) | 69 (77%) | 66 (88%) |
| Semitendinosus | 7 (4%) | 3 (3%) | 4 (5%) |
| Semimembranosus | 23 (14%) | 18 (20%) | 5 (7%) |
| Oedema dimensions | |||
| Craniocaudal length (cm) | 13.7±6.8 | 15.3±6.9 | 11.7±6.1 |
| CSA (% of muscle CSA) | 23.1 (IQR: 9.9–48.2) | 16.8 (IQR: 8.0–46.4) | 30.5 (IQR: 15.5–49.3) |
| Intramuscular tendon injury | |||
| No tendon disruption | 96 (58%) | 53 (59%) | 43 (57%) |
| Free tendon disruption | 5 (3%) | 5 (6%) | 0 (0%) |
| Intramuscular tendon disruption | 64 (39%) | 32 (36%) | 32 (43%) |
| <50% of tendon CSA | 12 (7%) | 5 (6%) | 7 (9%) |
| 50%–99% of tendon CSA | 28 (17%) | 14 (16%) | 14 (19%) |
| 100% of tendon CSA | 24 (15%) | 13 (14%) | 11 (15%) |
| Biceps femoris | 48 (75%) | 19 (59%) | 29 (91%) |
| Biceps femoris and semitendinosus | 8 (13%) | 8 (25%) | 0 (0%) |
| Semitendinosus | 0 (0%) | 0 (0%) | 0 (0%) |
| Semimembranosus | 8 (13%) | 5 (16%) | 3 (9%) |
| Longitudinal tendon disruption | |||
| Length of intramuscular tendon disruption (cm) | 6.2±2.8 | 6.8±2.2 | 5.7±3.2 |
| Retraction (cm) | 3.7 (IQR: 2.0–5.9) | 3.3 (IQR: 1.5–6.7) | 3.7 (IQR: 2.1–5.9) |
| Waviness | |||
| Present | 37 (22%) | 19 (21%) | 18 (24%) |
| Absent | 128 (78%) | 71 (79%) | 57 (76%) |
Normally distributed data are presented as a mean with SD and non-normally distributed data as a median with IQR.
CSA, cross-sectional area.