Summary of British Athletics Muscle Injury Classification (* if any characteristics of a higher grade injury are present the injury is graded at the highest grade)
| Grade | Description | MRI (day 2) |
|---|---|---|
| 0a 0b | Focal area of muscle pain usually following exercise Generalised muscle pain following unaccustomed exercise | MRI normal MRI normal or patchy high signal change throughout one or more muscles |
| Grade | Description | MRI |
| 1a 1b | Small myofascial tear Small muscle-tendon junction tear | High signal change evident at the fascial border with less than 10% extension into muscle belly Craniocaudal distance of <5 cm High signal change of less than 10% cross-sectional area of muscle at the muscle-tendon junction High signal change of craniocaudal length <5 cm (may note fibre disruption of <1 cm) |
| Grade | Description | MRI |
| 2a 2b 2c | Moderate myofascial tear Moderate muscle-tendon junction tear Moderate sized intratendinous tear | High signal change evident at fascial border with extension into the muscle High signal change cross-sectional area of between 10% and 50% at maximal site High signal change of craniocaudal length >5 and <15 cm Architectural fibre disruption usually noted over less than 5 cm High signal change evident at the muscle-tendon junction High signal change cross-sectional area of between 10% and 50% at maximal site High signal change of craniocaudal length >5 and <15 cm Architectural fibre disruption usually noted over less than 5 cm High signal change extends into the tendon with longitudinal length of tendon involvement <5 cm Cross-sectional area of tendon involvement <50% of maximal tendon cross-sectional area No loss of tension or discontinuity within the tendon |
| Grade | Description | MRI |
| 3a 3b 3c | Extensive myofascial tear Extensive muscle-tendon junction tear Extensive intratendinous tear | High signal change evident at fascial border with extension into the muscle High signal change cross-sectional area of greater than 50% at maximal site High signal change of craniocaudal length of greater than 15 cm Architectural fibre disruption usually noted over more than 5 cm High signal change cross-sectional area of greater than 50% at maximal site High signal change of craniocaudal length of greater than 15 cm Architectural fibre disruption usually noted over more than 5 cm High signal change extends into the tendon Longitudinal length of tendon involvement >5 cm Cross-sectional area of tendon involvement >50% of maximal tendon cross-sectional area There may be loss of tendon tension although no discontinuity is evident |
| Grade | Description | MRI |
| 4 4c | Full thickness tear of muscle Full thickness tear of tendon | Complete discontinuity of the muscle with retraction Complete discontinuity of the tendon with retraction |