Hamstring Strain

**The hamstrings** are a group of three muscles at the back of the thigh: 1. **Biceps femoris** (long and short heads) — lateral hamstring 2. **Semitendinosus** — medial hamstring 3. **Semimembranosus** — medial hamstring These muscles span TWO joints (hip extension AND knee flexion), making them particularly vulnerable to injury during high-speed activities where they're lengthening (eccentric contraction) while generating force. **Where Hamstring Strains Occur:** The hamstring complex is most vulnerable at the **musculotendinous junction** — where the muscle transitions to the tendon. Specifically: - **Proximal (upper) hamstring** — at the ischial tuberosity (sit bone) - **Mid-substance** — within the muscle belly - **Distal (lower) hamstring** — at the knee attachment **Most Common: Biceps Femoris (Long Head)** - **>80% of hamstring strains** - Particularly at the proximal musculotendinous junction - Vulnerable due to its biarticular function and long range **Mechanism of Injury:** **Sprint-Type Injury (Most Common):** - Occurs during **terminal swing phase** of sprinting - Hamstring is lengthening rapidly (eccentric contraction) - Generating force to decelerate the swinging leg - High forces during eccentric loading - Typically affects biceps femoris **Stretch-Type Injury:** - Occurs during extreme stretch (e.g., kicking, splits, dance) - Often involves semimembranosus or proximal tendon - Slower onset of pain - Often longer recovery time **Severity Classification (Munich Consensus):** **Type 1: Functional Muscle Disorder** - 1A: Fatigue-induced - 1B: Delayed onset muscle soreness - No structural damage on imaging - Recovery: 1-7 days **Type 2: Neuromuscular Muscle Disorder** - 2A: Spinal-related - 2B: Muscle-related - Mostly normal MRI - Recovery: 1-2 weeks **Type 3: Partial Muscle Tear** - 3A: Minor partial muscle tear (<5cm) - 3B: Moderate partial muscle tear (>5cm) - Visible on MRI - Recovery: 2-8 weeks **Type 4: (Sub)Total Muscle Tear / Tendinous Avulsion** - Complete or near-complete tear - Tendon avulsion from bone - Often surgical - Recovery: 3-6 months **Why Recurrence Is So Common:** - Returning to sport too early - Inadequate rehabilitation (especially eccentric strength) - Persistent strength deficits not fully addressed - Resumption of high-intensity training without progression - Untreated underlying issues (lumbar mechanics, hip mobility)

## Root Causes **Hamstring strains result from forces exceeding the hamstring's capacity, often during eccentric loading:** **Primary Mechanisms:** *Sprint Mechanism (Most Common):* - Terminal swing phase of sprinting - Hamstring rapidly lengthening (eccentric) - Generating force to decelerate the leg - Highest forces in the running cycle - Common in soccer, football, rugby, track *Stretch Mechanism:* - Extreme range of motion (kicking, splits) - Slower-onset pain - Often proximal injury (semimembranosus) - Common in dance, gymnastics, martial arts **Risk Factors:** *Modifiable:* - **Eccentric strength deficits** — major modifiable risk - **Inadequate warm-up** - **Fatigue** — late game increased risk - **Poor flexibility** — though debated - **Insufficient training load** — under-prepared muscles - **Inadequate progression** in training - **Lumbar mechanics** issues - **Hip mobility** restrictions *Non-Modifiable:* - **Previous hamstring injury** — single biggest risk (3-6x risk) - **Age** — risk increases with age in athletes - **Male sex** (in same sports) - **Race/ethnicity** — varies by population - **Sport** — sprinting/cutting highest risk *Anatomic:* - **Anterior pelvic tilt** - **Lumbar hyperlordosis** - **Hip flexor tightness** — increases pelvic tilt - **Poor lumbopelvic control** - **Leg length discrepancy** **The Critical Risk: Previous Injury** Previous hamstring injury is the single biggest risk factor — increasing recurrence risk 3-6x. Reasons: - **Strength deficits persist** — even after return to sport - **Scar tissue** alters muscle mechanics - **Neuromuscular changes** — altered firing patterns - **Inadequate rehabilitation** — return to sport too early - **Modified movement patterns** — compensations **Why Recurrence Rates Are 30-50%:** - Premature return to sport before full recovery - Inadequate eccentric strengthening - Failure to address underlying biomechanical issues - Insufficient sport-specific rehabilitation - Resumption of full-speed running too quickly

## Treatment Phases **Hamstring strain treatment follows phases — return-to-sport criteria are evidence-based:** ## Phase 1: Acute Management (Days 1-7) **Initial Management:** - **POLICE** protocol (Protection, Optimal Loading, Ice, Compression, Elevation) - Avoid PRICE (Rest is now considered too restrictive) - **Optimal loading** within pain limits — promotes healing - Ice 15-20 minutes every 2-3 hours - Compression bandage - Elevation when possible - **Crutches** if can't walk normally **Activity:** - Walking as tolerated (pain-free) - Gentle pain-free range of motion - Avoid sudden movements - Avoid stretching in early days **Medications:** - **Acetaminophen** preferred over NSAIDs initially - NSAIDs may impair healing if used long-term - Limit NSAIDs to 5-7 days max if used ## Phase 2: Sub-Acute Rehabilitation (Days 7-21) **Progressive Loading:** - Pain-free range of motion exercises - Gentle isometric strengthening - Progressive resistance training - Pool walking - Stationary cycling (low resistance) **Specific Exercises:** - **Bridges** (single and double leg) - **Hip thrusts** (light) - **Hamstring curls** (machine, then free) - **Romanian deadlifts** (very light) - **Glute strengthening** - **Core work** **Pain Management:** - Pain monitoring during exercise - Activities should produce no pain - Mild discomfort acceptable but not pain - Modify if pain occurs ## Phase 3: Strengthening and Functional (Days 14-42) **Eccentric Training (Critical):** The single most important intervention is **eccentric hamstring strengthening**: **Nordic Hamstring Exercise:** - Kneel on ground with feet held in place - Slowly lower torso forward, controlling with hamstrings - 3 sets of 5-12 reps - Reduces injury risk by 50-65% - Should be a permanent part of training **Other Eccentric Exercises:** - **Single-leg Romanian deadlifts** - **Glute-ham raises** - **Razor curls** - **Eccentric leg curls** **Progressive Loading:** - Start with bodyweight - Progress to weighted exercises - Increase eccentric component - Sport-specific movements ## Phase 4: Sport-Specific (Days 28-60) **Running Progression:** - Walk-jog-run intervals - Progressive speed increase - Sport-specific cutting/turning - Plyometrics - Sprint mechanics work **Return-to-Sport Criteria (Must Meet ALL):** - **Pain-free** at full sprinting speed - **Strength symmetry** (≥90% of uninjured side) - **Eccentric strength** symmetry - **Full functional testing** completed - **Sport-specific drills** performed at full intensity - **Psychological readiness** ## Surgery (Rare) **Indications:** - **Complete proximal avulsion** with retraction >2 cm - **Failed conservative treatment** in athletes - **Tendon avulsion** with significant displacement - **Apophyseal avulsion** in adolescents (often) **Procedures:** - **Direct repair** with suture anchors - **Tendon reattachment** to ischium - **Tendon-to-tendon repair** for distal injuries **Outcomes:** - 80-90% return to pre-injury level - Recovery: 4-6 months - Better outcomes if surgery within 4 weeks of injury ## Critical Treatment Pearls **1. Don't Rush Return to Sport** - Premature return = high recurrence - Must meet ALL return-to-sport criteria - Strength deficits often persist beyond pain resolution **2. Eccentric Training Is Essential** - Nordic hamstring exercises reduce injury risk 50-65% - Should be permanent training component - Cannot be substituted with concentric exercises **3. Address Underlying Issues** - Lumbar mechanics - Hip mobility - Pelvic tilt - Movement patterns **4. Manage Recurrence Risk** - Previous injury = biggest risk factor - Eccentric maintenance training - Adequate warm-up before sport - Avoid fatigued play (late game injuries) **5. Imaging When Severe** - MRI for moderate to severe injuries - Identifies high-risk features (significant retraction) - Guides surgical decisions - Sets realistic expectations ## Prevention Programs (Highly Effective) **Nordic Hamstring Program:** - 3 sets of 5-12 reps - 1-3 sessions per week - Reduces injury risk 50-65% - Standard for major sports teams **FIFA 11+ Program:** - Comprehensive injury prevention - Includes hamstring components - Implemented across world football - Reduces injury rates **Australian Football Hamstring Initiative:** - Comprehensive program - Eccentric exercises core - Reduced league-wide injury rates