Muscle Injury
Definition
- Clinical diagnosis = Acute onset muscle pain during activity, with localised tenderness, pain on resisted contraction or stretch, with or without bruising or a palpable defect
- Specify the muscle and the site, for example biceps femoris at the myotendinous junction
- Separate entities: delayed onset muscle soreness, cramps, myofascial trigger point and referred pain
Mechanism
- Most are non-contact. About 95% occur during high-speed running, acceleration, deceleration, kicking, stretching or change of direction. Only 5% are direct contact (contusion)
- The muscle is overloaded while lengthening, causing fibre or intramuscular tendon disruption
- Haematoma and oedema follow, then healing by regeneration and scar
- Muscle that crosses 2 joints are more prone to injury (e.g. Hamstring, Rectus femoris)
Risk factors
- Previous muscle strain
- Older age (less healing capacity)
- Altered biomechanics
- Training and match load
- Isolated strength measures did not predict injury
Common types
| Type | Mechanism | Typical muscles |
|---|---|---|
| Strain (indirect) | Eccentric overload during sprinting, kicking, stretching | Hamstrings, rectus femoris, adductor longus, gastrocnemius or soleus |
| Contusion (direct) | Direct blow with compression of muscle against bone | Quadriceps (e.g. in rugby) |
| Avulsion | Tendon pulled off bone or full-thickness disruption | Proximal hamstring, rectus femoris, adductors |
Diagnosis
- Mostly clinical diagnosis.
- History: mechanism, “pop”, previous injuries
- Examination:
- Look (bruising)
- Feel – Press (tenderness on palpation), Stretch (pain on passive stretch), Resist (pain or weakness on resisted contraction)
| Investigation | Finding |
|---|---|
| Ultrasound | Fibre disruption, haematoma, dynamic assessment |
| MRI | Oedema, fibre and tendon disruption, extent and site |
| X-ray | Avulsion fracture, myositis ossificans after contusion |
Grading
Two systems are in common use. BAMIC was the most used for hamstring injury among experts surveyed in the London consensus.
| System | Basis | Categories |
|---|---|---|
| Munich consensus (MCS) | Clinical and imaging | Functional (type 1 to 2), structural (type 3 partial tear, type 4 complete tear), contusion separate |
| British Athletics Muscle Injury Classification (BAMIC) | MRI | Grade 0 to 4 by extent of injury, plus a, b, c by site: a myofascial, b muscle-tendon junction, c intratendinous |
- Both correlate moderately with return to play
- Intratendinous (c) injuries had the longest layoff – about 39 days
- Myotendinous junction (b) – 18 days
- Myofascial (a) – about 14 days
Management
- Early, progressive, individualised rehabilitation is first line. Surgery is rarely needed
- Include lengthening (eccentric) loading
- Progress by capacity and symptoms, not by timing
- Sequence: confirm diagnosis and grade > early protected loading > progressive loading > running and sprinting > sport-specific training > return to play (if criteria met)
- Counsel that reinjury risk is highest in the first weeks after return
Return to play
- No single test decides return. Combine pain, strength, flexibility and sport-specific movement at maximum speed
- Pain is the most commonly used criterion but should not be used alone
- Set the rehabilitation end point by the demands of match play
- Pain-free sprinting is the supported criteria for return
- Experts did not agree on numeric strength or flexibility cut-off points
Red flags and when to refer
Same-day assessment (to ED or Orthopaedics)
- Suspected complete rupture or avulsion: audible pop, large bruising, palpable defect or retraction, marked weakness.
- Tense, swollen thigh or calf with pain out of proportion after a contusion: exclude compartment syndrome
Refer to sports medicine
- Suspected grade 2 or above injury, or intratendinous injury
- No progress after 1 month of properly delivered rehabilitation
- Recurrent injury in the same muscle
- Elite or competitive athlete with an urgent return-to-play timeline
- Persistent pain or loss of motion after a contusion: exclude myositis ossificans
- Considering any injection or procedural adjunct such as PRP
This summary is for educational use by healthcare professionals and does not replace clinical judgement.
References
- Paton, B. M., et al. (2023). London International Consensus and Delphi study on hamstring injuries part 1: Classification. British Journal of Sports Medicine, 57(5), 254–265. https://doi.org/10.1136/bjsports-2021-105371
- Paton, B. M., et al. (2023). London International Consensus and Delphi study on hamstring injuries part 3: Rehabilitation, running and return to sport. British Journal of Sports Medicine, 57(5), 278–291. https://doi.org/10.1136/bjsports-2021-105384
- Schönnagel, B., et al. (2025). Muscle injuries in 90 professional football players over 10 consecutive seasons: A comparison of two classification systems and their association with return-to-play time. Scandinavian Journal of Medicine & Science in Sports, 35(10). https://doi.org/10.1111/sms.70147
- Eggleston, L., et al. (2020). High-grade intramuscular tendon disruption in acute hamstring injury and return to play in Australian Football players. Scandinavian Journal of Medicine & Science in Sports, 30(6), 1073–1082. https://doi.org/10.1111/sms.13642
- Green, B., et al. (2020). Recalibrating the risk of hamstring strain injury (HSI): A 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport. British Journal of Sports Medicine, 54(18), 1081–1088. https://doi.org/10.1136/bjsports-2019-100983
- Rudisill, S. S., et al. (2021). Evidence-based management and factors associated with return to play after acute hamstring injury in athletes: A systematic review. Orthopaedic Journal of Sports Medicine, 9(11). https://doi.org/10.1177/23259671211053833
- Afonso, J., et al. (2023). Effectiveness of conservative interventions after acute hamstrings injuries in athletes: A living systematic review. Sports Medicine, 53(3), 615–635. https://doi.org/10.1007/s40279-022-01783-z
- Bru-Ruiz, J. J., et al. (2026). Establishing weighted criteria for return to play after hamstring injury: A systematic review and methodological quality analysis. BMC Musculoskeletal Disorders, 27(1). https://doi.org/10.1186/s12891-026-10072-z
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Medical disclaimer: this article is general information, not personal medical advice. Always consult a qualified doctor about your own situation.