Acute Hamstring Injury

History:

• •Sudden sharp posterior thigh pain during sprinting, acceleration, or high-velocity kicking. Often a pop or pulling sensation
• •Stretching type: pain at end-range hip flexion with knee extension (high kick, splits)
• •Inability to continue activity
• •Swelling and bruising (may track distally to the knee over 24-72 hours)

Examination:

• •Tenderness in the mid-posterior thigh / MTJ region suggests sprinting type; pain nearer the ischial tuberosity suggests stretching type or proximal tendon involvement
• •Palpable defect in higher-grade tears
• •Reduced and painful active knee flexion against resistance
• •Painful passive straight-leg raise; compare with the contralateral side
• •In adolescents, palpate the ischial tuberosity carefully

Differential diagnoses:

• •Proximal hamstring tendinopathy: chronic insidious onset, pain with sitting. Different entity
• •Lumbar radiculopathy (L5/S1): back pain, dermatomal pattern, positive SLR with dermatomal reproduction
• •Deep gluteal syndrome: deep buttock pain with sciatic irritation
• •Ischial tuberosity apophyseal avulsion (adolescents)
• •DVT: consider in atypical presentations

Acute hamstring injury is primarily a clinical diagnosis. Imaging is used when grading will change management.

• •MRI: the most informative modality. Allows BAMIC grading and site characterisation. Optimal timing is within the first few days, classically around 48-72 hours, when oedema has declared itself. Particularly important when intratendinous extension or significant retraction needs confirming
• •Ultrasound: accessible and useful for dynamic assessment and superficial injuries. Operator-dependent. Limited for deep intratendinous extension (the BFLH central tendon sits deep in the muscle and can be obscured by acoustic shadowing) - a key limitation when tendon involvement changes management
• •Plain X-ray: AP pelvis to exclude ischial tuberosity apophyseal avulsion in adolescents, with bilateral comparison

BAMIC and MRI findings inform prognosis, but return-to-play is criteria-based, not calendar-based. Outcome measures include the Askling H-test (active high kick with knee extension) as one adjunct to assess residual apprehension.

The vast majority of acute hamstring injuries are managed non-operatively. UK practice follows NICE CKS (Sprains and Strains) for primary-care fundamentals and BJSM / London International Consensus / Aspetar principles for sports-specific care.

Acute management (first 48-72 hours):

• •POLICE framework (Protection, Optimal Loading, Ice, Compression, Elevation). Severe injuries may warrant a brief protection / off-loading period with crutches before progressive loading begins
• •Paracetamol first-line; topical NSAID is a reasonable alternative per NICE CKS
• •Oral NSAIDs can be considered short-term, but many SEM clinicians avoid them in the first 48 hours given theoretical concerns about impairing satellite-cell-driven regeneration

Early controlled loading within days rather than prolonged rest is the standard. Platelet-rich plasma is not supported for routine use by current evidence.

Indications for early surgical opinion:

• •Ischial tuberosity apophyseal avulsion with more than 2 cm retraction (adolescents)
• •Suspected proximal hamstring avulsion: complete (3-tendon) ruptures and 2-tendon avulsions with meaningful retraction (typically over 2 cm) in active or high-demand patients
• •Major weakness or sciatic symptoms suggesting significant retraction
• •Chronic proximal tendinous avulsion with persistent functional loss

Delayed proximal repair becomes technically harder with worse outcomes; early specialist assessment is the key principle.

Referral pathway: SEM specialist or MSK physiotherapy for BAMIC 3-4, suspected proximal tendon involvement, recurrent injury, or athletes with RTP targets. Urgent referral for suspected avulsion, adolescent ischial avulsion, or neurological features. Consider bone health and RED-S screening in any athlete with recurrent injury or features of low energy availability.

Rehabilitation is the single most important determinant of outcome; inadequate rehabilitation is the strongest modifiable predictor of re-injury. Progress is criteria-based, individual, and guided by BAMIC site and severity.

Phase 1 (acute protection, 0-5 days): POLICE. Early pain-free isometric loading (prone isometric knee flexion, bridging variations). Maintain cardiovascular fitness with non-provocative cross-training.

Phase 2 (early loading, 5 days to 2 weeks): progressive isotonic strengthening. Introduce lengthened-position loading when tolerated. The Askling L-protocol (Extender, Diver, Glider) is one well-described option that targets the lengthened position; trial evidence for its superiority is mixed, but the principle of lengthened-position loading is well supported.

Phase 3 (progressive loading, 2-6 weeks): progressive eccentric loading, using exercises such as the Nordic hamstring curl. Add running progression (straight-line jogging to accelerations to sprint mechanics), change of direction, and sport-specific drills. Address contributing factors, particularly anterior pelvic tilt via gluteal and core strengthening, which optimises pelvic position during high-speed running.

Phase 4 (return to sport, variable): graduated exposure to maximal sprinting. Return-to-sport criteria (individualised, no single gatekeeper):

• •Pain-free progression to maximal sprinting
• •Adequate outer-range eccentric and isometric strength for the athlete's sport - ideally assessed with objective tools (isokinetic dynamometry, NordBord)
• •Completion of unrestricted training and sport-specific drills
• •Absence of clinically meaningful apprehension (psychological readiness)
• •The Askling H-test may be used as one adjunct, not a sole gatekeeper

Prevention: the Nordic hamstring exercise, delivered as a progressive programme, has the strongest prevention evidence (approximately 50% reduction in HSI incidence in team sports) and is a core component of FIFA 11+. Pre-season conditioning with eccentric loading, training-load management, and addressing modifiable factors (pelvic control including anterior tilt, hip flexibility, running mechanics) round out the prevention picture.

• •BAMIC (Pollock et al., BJSM 2014): UK-developed muscle injury classification grading severity (0-4) and site (a, b, c) on MRI; the "c" (intratendinous) suffix is the strongest prognostic marker.
• •Askling et al. mechanism and rehabilitation studies (BJSM 2007 onwards): defined the sprinting vs stretching mechanism distinction and the L-protocol of lengthened-position loading.
• •Petersen et al. Nordic hamstring exercise RCT (AJSM 2011) and subsequent meta-analyses: approximately 50% reduction in HSI incidence with eccentric Nordic exercise as part of FIFA 11+.
• •Aspetar Hamstring Consensus (BJSM 2015): clinical framework for diagnosis, classification, and return-to-play in acute HSI.
• •NICE CKS Sprains and Strains: UK primary-care management principles including POLICE, analgesia, and graduated loading.
• •London International Consensus on hamstring injury management: international expert framework for grading-to-rehabilitation translation.

• •Distinguish acute hamstring INJURY (sudden, MTJ, sprinting) from proximal hamstring TENDINOPATHY (chronic, ischial, sitting pain). Different entities, different management.
• •BFLH is most commonly involved in sprinting injuries; semimembranosus proximal tendon is the classic stretching-type site.
• •BAMIC site (a, b, c) often matters more than numerical grade. BFLH central tendon involvement (c) is a recognised high-risk pattern that prolongs rehabilitation.
• •Ischial tuberosity avulsion in an adolescent = urgent AP pelvis X-ray. Displacement over 2 cm is a surgical indication.
• •Surgery is considered early for proximal avulsions (complete or 2-tendon with significant retraction) in active patients. Delayed repair has worse outcomes.
• •Nordic hamstring exercise: strongest evidence is for PREVENTION (around 50% reduction in team sports), not as a standalone rehabilitation intervention. The prevention-vs-rehabilitation distinction is commonly tested.
• •Previous injury is the strongest overall risk factor; inadequate rehabilitation is the strongest modifiable predictor of re-injury.