HAMSTRING INJURIES - MUSCLE STRAIN AND PROXIMAL AVULSION
Biceps Femoris Most Common | Grading I-III | Proximal Repair if Greater Than 2cm Retraction
MUSCLE STRAIN GRADING
Critical Must-Knows
- Biceps femoris long head (BFlh) most commonly injured - eccentric loading at late swing phase
- Proximal hamstring avulsion requires surgical repair if greater than 2cm retraction or more than 2 tendons
- MRI essential for surgical planning - measure retraction distance and number of tendons involved
- Nordic hamstring exercises are evidence-based for prevention and rehabilitation
- Return to sport requires hamstring:quadriceps ratio greater than 0.8 and Askling H-test negative
Examiner's Pearls
- "Hamstring injuries peak at late swing phase (eccentric contraction during deceleration)
- "Proximal avulsion off ischial tuberosity more common in water-skiing, splits injuries
- "Mid-substance tears (myotendinous junction) more common in sprinting, kicking sports
- "Bent-knee stretch test distinguishes proximal (positive) from mid-substance (negative) tears
Clinical Imaging
Hamstring Injury MRI Findings
Critical Hamstring Injury Exam Points
Anatomy and Mechanism
Three muscles: semimembranosus (SM), semitendinosus (ST), biceps femoris long head (BFlh). BFlh most commonly injured (80%) due to dual innervation (tibial + peroneal) causing uncoordinated contraction. Eccentric load during late swing phase of running.
Grading System
Grade I: Mild strain, less than 10% fibres disrupted. Grade II: Moderate partial tear, 10-50% disruption. Grade III: Complete tear or proximal avulsion. MRI confirms grading - Grade II shows feathery oedema, Grade III shows gap and retraction.
Surgical Indications
Proximal hamstring avulsion: Surgery if retraction greater than 2cm OR more than 2 tendons avulsed OR failure of conservative management. Acute repair (within 4 weeks) has better outcomes than delayed. Use suture anchors to ischial tuberosity.
Return to Sport Criteria
Functional criteria mandatory: H:Q ratio greater than 0.8, Askling H-test negative, pain-free sprinting, return to sport-specific drills. Premature return (within 3 weeks for Grade II) leads to 34% re-injury rate. Minimum 6 weeks for Grade II, 12 weeks post-op for Grade III.
Quick Decision Guide - Hamstring Injury Management
| Injury Type | Clinical Features | Treatment | Return Timeline |
|---|---|---|---|
| Grade I Strain | Mild pain, minimal loss of motion, able to walk normally | RICE, gentle stretching, progressive loading | 2-3 weeks (when Askling test negative) |
| Grade II Partial Tear | Moderate pain, palpable defect, limp, reduced ROM | Conservative: progressive eccentric exercises, Nordic hamstrings | 4-8 weeks (functional criteria essential) |
| Grade III Proximal Avulsion (less than 2cm) | Severe pain, bruising, weakness, positive bent-knee test | Conservative trial (non-operative) with close monitoring | 12-16 weeks (may need surgery if fails) |
| Grade III Proximal Avulsion (greater than 2cm) | Complete loss of hamstring contour, palpable gap, severe weakness | URGENT surgical repair (within 4 weeks optimal) | 12 weeks minimum post-op (functional testing required) |
| Chronic Proximal Avulsion | Persistent weakness, sitting pain (ischial), functional limitation | Delayed surgical reconstruction (may need graft augmentation) | 16-24 weeks post-op (lower success than acute) |
BICEPSBICEPS - The Most Injured Hamstring
Memory Hook:BICEPS is the muscle that gets injured when you sprint - think of the biceps femoris as the sprint muscle with dual innervation making it vulnerable!
MPCGRADING - Muscle Strain Classification
Memory Hook:MPC = Mild, Partial, Complete - the three grades you MUST know for hamstring classification!
SURGICALSURGICAL - Indications for Proximal Repair
Memory Hook:SURGICAL criteria for proximal hamstring avulsion - greater than 2cm retraction is the key threshold!
NORDICNORDIC - Evidence-Based Prevention and Rehab
Memory Hook:NORDIC exercises are the gold standard for both preventing and rehabilitating hamstring injuries - remember the H:Q ratio of 0.8!
Overview and Epidemiology
Hamstring injuries are among the most common muscle injuries in sport, particularly affecting sprinters, footballers (AFL, soccer, rugby), and track athletes. The injury spectrum ranges from mild muscle strains to complete proximal avulsions requiring surgical repair.
Epidemiology:
- Incidence: 12-16% of all sports injuries in running-based sports
- Peak age: 20-40 years (peak athletic participation)
- Gender: Male to female ratio approximately 2:1 (higher male participation in sprinting sports)
- Location:
- Biceps femoris long head: 80% of injuries
- Semimembranosus: 15%
- Semitendinosus: 5%
Mechanism of injury:
- Eccentric overload: Late swing phase of sprinting (muscle lengthening under load)
- Sudden acceleration/deceleration: Change of direction, explosive sprinting
- Proximal avulsion: Extreme hip flexion with knee extension (splits, water-skiing)
- Chronic overuse: Accumulation of microtears in high-volume training
Why Biceps Femoris is Most Vulnerable
The biceps femoris long head has dual innervation (tibial nerve to medial portion, common peroneal nerve to lateral portion), leading to uncoordinated muscle activation. It also has the longest fascicle length and greatest excursion during running, making it most susceptible to eccentric injury at the myotendinous junction.
Australian context:
- AFL epidemic: Hamstring injuries account for 15-20% of all AFL injuries
- Economic impact: Average 3-4 weeks missed playing time (Grade II)
- Re-injury burden: 34% re-injury rate if returned within 3 weeks (premature)
Pathophysiology and Mechanisms
Hamstring muscle group:
The posterior thigh muscles consist of three distinct muscles:
Hamstring Muscle Anatomy
| Muscle | Origin | Insertion | Innervation | Function |
|---|---|---|---|---|
| Biceps femoris (long head) | Ischial tuberosity (medial facet) | Fibular head | Tibial nerve (medial) + Common peroneal (lateral) | Knee flexion, hip extension |
| Semitendinosus | Ischial tuberosity (medial facet) | Proximal medial tibia (pes anserinus) | Tibial nerve | Knee flexion, hip extension, tibial internal rotation |
| Semimembranosus | Ischial tuberosity (lateral facet) | Posterior medial tibial condyle | Tibial nerve | Knee flexion, hip extension |
Biceps Femoris Vulnerability
The biceps femoris long head (BFlh) has dual innervation from both the tibial nerve (L5, S1, S2) and the common peroneal nerve (L4, L5, S1), creating a neuromuscular coordination challenge. The medial and lateral portions contract with slightly different timing, predisposing to microtears at the myotendinous junction during high-speed eccentric loading.
Biomechanics of injury:
Eccentric Contraction
Late swing phase of running (70-80% of gait cycle): hamstring muscle lengthens while contracting to decelerate the leg. Peak force occurs just before foot strike. This eccentric load (up to 2.5x body weight) exceeds muscle capacity in fatigue.
Myotendinous Junction
Most common tear location (Grade I-II): junction between muscle belly and proximal tendon. This zone has poorest blood supply and highest mechanical stress concentration during eccentric loading.
Proximal Avulsion
Ischial tuberosity avulsion (Grade III): occurs with extreme hip flexion + knee extension (splits, water-skiing, martial arts kicks). Complete separation of one or more tendons from bony insertion. Requires surgical repair if greater than 2cm retraction.
Risk Factors
Modifiable: Inadequate warm-up, previous hamstring injury (greatest risk factor), hamstring weakness (H:Q ratio less than 0.6), fatigue, limited flexibility. Non-modifiable: Age greater than 30, previous injury, BFlh anatomy (long fascicles).
Blood supply:
- Perforating branches of profunda femoris artery
- Inferior gluteal artery (proximal portion)
- Myotendinous junction has relatively poor vascularity (watershed zone)
Phase of running cycle:
| Phase | Hamstring Activity | Risk |
|---|---|---|
| Early swing | Minimal activity | Low risk |
| Mid-swing | Concentric contraction (hip extension) | Low risk |
| Late swing | Eccentric contraction (deceleration) | HIGH RISK - peak injury phase |
| Stance | Isometric contraction | Low risk |
Classification Systems
British Athletics Muscle Injury Classification (BAMIC)
The standard grading system for hamstring muscle injuries:
| Grade | MRI Findings | Clinical Features | Return Time |
|---|---|---|---|
| Grade 0 | Normal MRI, no oedema | Hamstring tightness, no structural injury | 1-3 days |
| Grade I | Less than 10% cross-sectional area, feathery oedema | Mild pain, minimal strength loss, able to continue activity | 2-3 weeks |
| Grade II | 10-50% cross-sectional area, visible fibre disruption | Moderate pain, palpable defect, significant strength loss, limp | 4-8 weeks |
| Grade III | Greater than 50% or complete tear, gap visible | Severe pain, visible deformity, complete loss of function | 12+ weeks or surgery |
MRI Essential for Grading
MRI is mandatory for accurate grading and surgical planning. T2-weighted sequences show muscle oedema (bright signal). Measure: (1) Cross-sectional area involved (percentage), (2) Longitudinal length of injury, (3) Retraction distance (for Grade III). These measurements predict return-to-sport timeline.
Clinical Presentation and Assessment
History:
Mechanism
- Sprinting/acceleration: Mid-substance or proximal MTJ tear
- Sudden deceleration/change direction: Eccentric overload
- Extreme hip flexion + knee extension: Proximal avulsion (splits, water-skiing)
- Acute pop or tear sensation: Suggests Grade II-III
Symptoms
- Pain location: Posterior thigh (mid-substance) vs ischial/buttock (proximal)
- Severity: Mild (continue playing) vs severe (immediate cessation)
- Functional loss: Inability to sprint, kick, or accelerate
- Previous injury: Most significant risk factor for re-injury
Physical examination:
Clinical Examination Findings
| Finding | Grade I | Grade II | Grade III/Avulsion |
|---|---|---|---|
| Gait | Normal or minimal limp | Antalgic gait, avoids heel strike | Severe limp, unable to bear weight |
| Inspection | Minimal swelling | Swelling, bruising appears 24-48h | Visible deformity, loss of hamstring contour, extensive bruising |
| Palpation | Tender but no defect | Palpable defect, tender area | Large palpable gap, ischial tenderness |
| Range of motion | Minimal limitation, pain at end range | Limited active knee flexion, painful passive stretch | Severe limitation, unable to flex knee against gravity |
| Strength | 4 out of 5 (mild weakness) | 3 out of 5 (moderate weakness) | 1-2 out of 5 or complete loss of function |
Special tests:
Askling H-Test (Return to Sport Clearance)
Purpose: Functional assessment for return-to-sport readiness
Technique:
- Patient standing, hip neutral
- Actively flex knee maximally (heel to buttock)
- Extend hip while maintaining knee flexion
- Hold position for 5 seconds
Positive test:
- Pain or discomfort during test
- Unable to complete full range
- Apprehension or fear of injury
Interpretation:
- Negative test (pain-free): Safe to return to sport
- Positive test: Continue rehabilitation, re-test weekly
Essential Return-to-Sport Test
The Askling H-test is the gold standard functional test. Athletes must pass (pain-free) before returning to sprinting or sport. Sensitivity 80%, specificity 85% for predicting safe return. Combine with H:Q strength ratio greater than 0.8 for optimal decision-making.
Sitting Pain = Proximal Avulsion
Chronic sitting pain (ischial discomfort) is pathognomonic for proximal hamstring pathology. If a patient reports pain sitting on hard surfaces, especially weeks after injury, think proximal avulsion or incomplete healing. This indicates surgical consultation is warranted.
Investigations
Imaging protocol:
Hamstring Injury Imaging Pathway
Initial assessment based on history and physical examination. Determine severity clinically. Imaging not required for Grade 0-I if diagnosis clear.
Indications: Grade II or suspected Grade III, surgical planning needed, elite athlete. Sequences: T2-weighted (shows oedema), T1-weighted (shows anatomy), coronal and axial views. Measure: Cross-sectional area involved, longitudinal extent, retraction distance (if Grade III).
Dynamic assessment: Real-time imaging, operator-dependent. Can assess tendon retraction, haematoma. Less sensitive than MRI for muscle oedema. Useful for serial monitoring of healing.
If not progressing: Reassess with MRI to check healing. Persistent oedema or enlarging gap suggests need for intervention. Serial ultrasound for monitoring rehabilitation progress.
MRI findings by grade:
| Grade | T2 Signal | Muscle Architecture | Measurements Required |
|---|---|---|---|
| Grade I | Feathery high signal, less than 10% area | Muscle fibres intact | Note location, no measurement needed |
| Grade II | High signal, 10-50% area, partial fibre disruption | Partial gap, some fibres torn | Measure cross-sectional area percentage, length |
| Grade III | Complete gap, retracted tendon, haematoma | Complete disruption, visible retraction | Measure retraction distance from ischial tuberosity, count tendons involved |
MRI Surgical Planning
For proximal avulsion, MRI must document: (1) Number of tendons avulsed (ST, SM, BFlh), (2) Retraction distance (measure from ischial tuberosity to proximal tendon edge on coronal view), (3) Muscle quality (fatty infiltration suggests chronic injury), (4) Haematoma size. These factors guide surgical approach and prognosis.
Other investigations:
- X-ray: Only if concern for ischial tuberosity avulsion fracture (rare, adolescents)
- CT: Not routinely indicated
- Diagnostic ultrasound: Useful for serial monitoring, less detailed than MRI
Management Algorithm
Non-Operative Management (Grade I-II)
Goal: Progressive loading to restore strength and prevent re-injury
Rehabilitation Timeline
RICE protocol: Rest from aggravating activities, Ice 15-20 minutes every 2-3 hours, Compression bandage, Elevation. Pain management: NSAIDs (ibuprofen 400mg TDS) for 3-5 days. Gentle ROM: Pain-free knee flexion/extension, avoid stretching. Crutches if needed: For Grade II with significant limp.
Isometric exercises: Pain-free hamstring contractions (seated knee flexion against resistance). Gentle stretching: Pain-free range, no aggressive stretching (delays healing). Progressive walking: Increase distance and speed as tolerated. Pool exercises: Aqua jogging (unloaded).
Nordic hamstring curls: 3 sets of 5-8 reps, 3x per week (EVIDENCE-BASED). Single-leg deadlifts: Eccentric loading with control. Progressive resistance: Increase load as strength improves. Avoid explosive movements: No sprinting or kicking yet.
Running progression: Light jogging → straight-line sprinting → change of direction. Plyometrics: Hopping, bounding (when Askling test negative). Sport drills: Kicking, acceleration (sport-specific). Strength testing: H:Q ratio must be greater than 0.8.
Criteria for return: (1) Askling H-test negative, (2) H:Q ratio greater than 0.8, (3) Pain-free full sprinting, (4) Completed sport-specific drills without symptoms. Minimum time: 2-3 weeks (Grade I), 4-8 weeks (Grade II). Re-injury prevention: Continue Nordic hamstrings 2x per week indefinitely.
Do Not Rush Return
Premature return (within 3 weeks for Grade II) leads to 34% re-injury rate. Athletes who complete full rehabilitation (including eccentric strengthening) have re-injury rate of only 12%. The key is achieving functional criteria (strength, Askling test, pain-free sprinting), NOT just time-based clearance.
Surgical Technique - Proximal Repair Detail
Pre-operative planning:
Consent Points
- Sciatic nerve injury: 1-3% (numbness, weakness, permanent risk)
- Infection: 2-5% (superficial wound infection most common)
- Re-rupture: 5-10% (if non-compliant with post-op protocol)
- Persistent weakness: 10-20% (especially chronic repairs)
- Sitting discomfort: May persist for 6-12 months
- Failure to return to sport: 10-20%
Equipment Checklist
- Suture anchors: 5.5mm x 3-5 anchors (plan for ischial tuberosity)
- Sutures: No.2 non-absorbable (Fiberwire or Ethibond)
- Retractors: Deep retractors for gluteus maximus and sciatic nerve
- Imaging: C-arm for anchor placement (lateral view confirms depth)
- Hip brace: Post-operative brace limiting flexion to 60 degrees
Detailed operative steps:
Step-by-Step Proximal Hamstring Repair
Patient positioning:
- Prone position on radiolucent table (allows C-arm access)
- Chest padding: Reduce pressure on chest and abdomen
- Pelvic bolsters: Support pelvis, allow hip mobility
- Knees padded: Protect patellae
- Arms: Positioned on arm boards or alongside body
Skin preparation:
- Wide prep from lumbar spine to mid-thigh bilaterally
- Include perineum in field (ischial access)
- Transparent adhesive drape for visualization
Incision:
- Palpate ischial tuberosity (bony prominence inferior to gluteal fold)
- Transverse incision (preferred) or longitudinal
- Centered over ischial tuberosity, 8-12cm length
- Deepen through subcutaneous fat
Deep dissection:
- Split gluteus maximus longitudinally along fibre direction
- Blunt dissection to avoid bleeding
- Identify sciatic nerve (lateral border of incision, deep to glut max)
- Place deep retractor to protect nerve (retract laterally)
Proper positioning and surgical approach are critical for safe access to the ischial tuberosity while protecting neurovascular structures.
Intraoperative troubleshooting:
Common Intraoperative Problems
| Problem | Cause | Solution |
|---|---|---|
| Cannot find tendons | Extensive retraction (greater than 10cm) | Extend incision distally, palpate along posterior thigh |
| Tendons won't reach bone | Chronic retraction, scarring | Consider allograft augmentation or accept tension |
| Sciatic nerve tented | Nerve adherent to scar or stretched | Mobilize nerve carefully, may need external neurolysis |
| Anchor pulls out | Poor bone quality or incorrect angle | Re-drill, use larger anchor, or add additional anchor |
Complications
Complications of Hamstring Injuries
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Re-injury (conservative) | 12-34% | Premature return, inadequate rehab, previous injury | Prevention: Nordic hamstrings, functional criteria, minimum 6 weeks |
| Chronic pain/weakness | 5-15% | Incomplete healing, inadequate rehab | Extended physiotherapy, consider PRP injection, surgical consultation |
| Sciatic nerve injury (post-op) | 1-3% | Intraoperative traction, anchor malposition | Observation (most resolve), EMG at 6 weeks, neurosurgery if persistent |
| Surgical site infection | 2-5% | Deep dissection, haematoma | Antibiotics, drainage if collection, debridement if deep |
| Re-rupture (post-surgical) | 5-10% | Non-compliance with brace, premature loading | Prevention: strict brace protocol 6 weeks, controlled rehab |
| Haematoma/seroma | 10-15% | Incomplete haemostasis | Observation if small, aspiration if large, drain if recurrent |
| Sitting discomfort | 20-40% (6-12 months) | Ischial tuberosity sensitivity, hardware prominence | Cushioned seating, time (resolves in 80%), hardware removal if persistent |
Re-Injury Prevention is Key
Re-injury rate is 34% if return to sport within 3 weeks for Grade II injuries, vs 12% with adequate rehabilitation. The key prevention strategies: (1) Nordic hamstring exercises 2x per week (51-70% reduction in injury), (2) Functional testing before clearance (Askling test, H:Q ratio), (3) Minimum time-based return (4-8 weeks Grade II, 12+ weeks post-op).
Postoperative Care and Rehabilitation
Post-Surgical Protocol (Proximal Hamstring Repair)
- Brace: Hip brace limiting flexion to 60 degrees (worn at all times except exercises)
- Weight-bearing: Toe-touch weight-bearing with crutches for 2 weeks
- ROM: Passive knee flexion/extension (no hip flexion beyond 60 degrees)
- Wound care: Keep dry, staples removed at 14 days
- Pain management: Paracetamol + tramadol (avoid NSAIDs - may impair healing)
- DVT prophylaxis: Enoxaparin 40mg daily for 14 days (extended if high risk)
- Brace: Continue hip brace (flexion limit 60 degrees)
- Weight-bearing: Progress to full weight-bearing as tolerated
- ROM: Gradually increase hip flexion (10 degrees per week target)
- Exercises: Isometric hamstring contractions (seated), quadriceps strengthening
- Pool therapy: Aqua walking (week 4+) for unloaded ROM
- No stretching: Avoid aggressive hamstring stretching (delays healing)
- Brace: Wean off brace at 6 weeks (if ROM adequate)
- ROM: Full hip flexion goal by 8 weeks
- Strengthening: Begin Nordic hamstring curls (3x per week)
- Progressive resistance: Single-leg deadlifts, hamstring curls
- Cycling: Stationary bike for endurance (low resistance)
- Avoid: Running, jumping, explosive movements
- Running progression: Light jogging on treadmill, progress to outdoor
- Eccentric focus: Continue Nordic hamstrings (key to success)
- Strength testing: H:Q ratio should be greater than 0.7 by 16 weeks
- Plyometrics: Hopping, bounding (if Askling test negative)
- Functional drills: Sport-specific movements
- Criteria for return:
- Askling H-test negative (pain-free)
- H:Q ratio greater than 0.8 (isokinetic testing)
- Pain-free full sprinting
- Completed sport-specific drills without symptoms
- Minimum time: 4-6 months post-surgery for high-demand athletes
- Ongoing: Continue Nordic hamstrings 2x per week indefinitely
Key rehabilitation principles:
Do's
- Strict brace compliance for 6 weeks (prevents re-rupture)
- Nordic hamstring curls from week 6 onwards (evidence-based)
- Progressive loading - increase gradually, monitor symptoms
- Functional testing before return (objective criteria)
Don'ts
- NO aggressive stretching first 12 weeks (delays healing)
- NO premature return (minimum 4 months for athletes)
- NO running before 12 weeks post-op
- DO NOT ignore pain - pain indicates excessive loading
Outcomes and Prognosis
Outcomes of conservative management (Grade I-II):
| Grade | Return to Sport | Re-injury Risk | Key Prognostic Factor |
|---|---|---|---|
| Grade I | 95-100% at 2-3 weeks | 10-15% | Compliance with Nordic exercises |
| Grade II | 85-95% at 6-8 weeks | 20-34% | Time to return (longer is better) |
Time-Based Return Reduces Re-injury
Athletes who return after 6 weeks for Grade II injuries have 12% re-injury rate, compared to 34% re-injury if returned within 3 weeks. Every additional week of rehabilitation reduces re-injury risk by approximately 5%. Functional criteria (H:Q ratio, Askling test) are more important than time alone.
Outcomes of surgical repair (proximal avulsion):
| Timing | Return to Sport | Strength Recovery | Patient Satisfaction |
|---|---|---|---|
| Acute (within 4 weeks) | 90-95% | 90-100% (isokinetic testing) | Excellent (90%) |
| Subacute (4-12 weeks) | 80-90% | 80-90% | Good (80%) |
| Chronic (greater than 12 weeks) | 65-80% | 70-80% | Fair (70%) |
Prognostic factors for good outcome:
Good Prognosis Factors
- Acute repair (within 4 weeks of injury)
- 2 or fewer tendons involved (vs complete 3-tendon)
- No muscle atrophy or fatty infiltration on MRI
- Young patient (less than 40 years)
- Compliant with post-op protocol (brace, restricted ROM)
- Nordic hamstring exercise program maintained
Poor Prognosis Factors
- Delayed repair (greater than 12 weeks)
- Complete 3-tendon avulsion with extensive retraction
- Chronic muscle changes (atrophy, fatty infiltration)
- Older patient (greater than 50 years)
- Non-compliance with rehabilitation
- Premature return to high-demand activities
Long-term outcomes:
- Sitting discomfort: Resolves in 80% by 12 months, 20% have persistent mild discomfort
- Strength: 90-95% recovery in acute repairs, 70-80% in chronic
- Return to pre-injury level: 85-90% in acute repairs
Evidence Base and Key Trials
Nordic Hamstring Exercise Prevention - Petersen et al
- Cluster RCT of 942 football players over one season
- Nordic hamstring exercise program vs standard training
- 51% reduction in hamstring injury incidence in intervention group
- 70% reduction in re-injury rate
- Exercise protocol: 3x per week during preseason, 1-2x per week in-season
Proximal Hamstring Repair Outcomes - Birmingham et al
- 52 patients undergoing proximal hamstring repair for complete avulsion
- Acute repair (within 4 weeks): 90% return to sport, mean time 6.2 months
- Chronic repair (greater than 4 weeks): 75% return to sport, mean time 8.5 months
- Strength recovery: 95% in acute group vs 79% in chronic group (isokinetic testing)
- Complications: 3.8% sciatic nerve palsy (all resolved), 5.8% re-rupture
Hamstring Re-injury Risk Factors - Hickey et al
- Systematic review and meta-analysis of hamstring re-injury risk factors
- Previous hamstring injury: Strongest risk factor (OR 2.7, 95% CI 2.1-3.3)
- Age greater than 25 years: Increased risk (OR 1.9)
- Return to sport within 3 weeks: 34% re-injury vs 12% if returned after 6 weeks
- Inadequate eccentric strength recovery: Major modifiable risk factor
MRI Grading and Return to Sport - Reurink et al
- 165 athletes with acute hamstring injuries, MRI within 5 days
- Cross-sectional area involvement on MRI predicted return time: less than 10% (mean 17 days), 10-50% (mean 42 days), greater than 50% (mean 73 days)
- Proximal MTJ injuries had longer recovery than distal MTJ
- Longitudinal extent greater than 10cm associated with prolonged recovery
Australian Football League Hamstring Injury Patterns - Orchard et al
- Analysis of 1716 hamstring injuries in AFL over 15 seasons
- Hamstring injuries account for 15% of all AFL injuries (most common muscle injury)
- Biceps femoris: 82% of injuries, Semimembranosus 10%, Semitendinosus 8%
- Re-injury rate: 12.6% overall, increased to 25% if returned within 3 weeks
- Average games missed: 2.7 (range 0-15)
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Acute Hamstring Strain in AFL Player
"A 26-year-old professional AFL footballer presents 24 hours after experiencing sudden posterior thigh pain while sprinting during a match. He felt a 'pop' and was unable to continue. On examination, he has a palpable defect in the mid-posterior thigh, tenderness over the biceps femoris, and reduced strength (3 out of 5) on resisted knee flexion. He can walk with a limp. What is your assessment and initial management?"
Scenario 2: Proximal Hamstring Avulsion in Water Skier
"A 35-year-old recreational water skier presents 1 week after sustaining an injury during a fall. He felt severe pain in the buttock and posterior thigh, heard a 'pop', and had immediate loss of function. MRI shows complete avulsion of all three hamstring tendons from the ischial tuberosity with 4cm of retraction. He is currently unable to flex his knee against gravity and has severe weakness. Walk me through your surgical planning and technique."
Scenario 3: Recurrent Hamstring Injury with Failure
"A 28-year-old semi-professional soccer player presents with his third hamstring injury in 12 months, all to the same leg (left biceps femoris). He returned to sport 3 weeks after the previous injury. MRI shows Grade II strain with 25% cross-sectional area involvement at the proximal MTJ. He is frustrated and wants to 'just get surgery to fix it once and for all'. How do you manage this complex situation?"
MCQ Practice Points
Anatomy Question
Q: Which hamstring muscle is most commonly injured and why? A: Biceps femoris long head (80% of injuries) due to: (1) Dual innervation (tibial + common peroneal nerves) causing uncoordinated contraction, (2) Longest fascicle length and greatest excursion during running, (3) Most eccentric loading at late swing phase. Injury typically occurs at the proximal myotendinous junction.
Classification Question
Q: What are the criteria for Grade II hamstring muscle strain? A: Grade II: (1) 10-50% cross-sectional area involvement on MRI, (2) Partial muscle fibre disruption with visible gap, (3) Feathery high signal on T2 MRI, (4) Clinical: Moderate pain, palpable defect, strength 3 out of 5, limp present. Return time: 4-8 weeks with appropriate rehabilitation.
Surgical Indications Question
Q: What are the indications for surgical repair of proximal hamstring avulsion? A: (1) Retraction greater than 2cm measured on MRI, (2) More than 2 tendons completely avulsed, (3) Complete 3-tendon avulsion (regardless of retraction), (4) Failed conservative trial (3 months) with persistent functional deficit, (5) Elite athlete with high functional demands. Acute repair (within 4 weeks) has better outcomes than chronic reconstruction.
MRI Interpretation Question
Q: What MRI findings predict longer return-to-sport time after hamstring injury? A: (1) Greater cross-sectional area involvement (greater than 25% = longer return), (2) Longitudinal extent greater than 10cm, (3) Proximal MTJ location (vs distal MTJ), (4) Complete tear with retraction (Grade III). MRI performed within 5 days accurately predicts timeline: less than 10% area = 17 days, 10-50% = 42 days, greater than 50% = 73+ days.
Prevention Question
Q: What is the evidence for Nordic hamstring exercises in injury prevention? A: Petersen et al (2011) RCT showed: (1) 51% reduction in primary hamstring injury incidence, (2) 70% reduction in re-injury rate, (3) Exercise protocol: 3x per week preseason, 1-2x per week in-season, (4) Eccentric strengthening at knee flexion angles of 0-45 degrees. This is the gold standard evidence-based prevention and rehabilitation exercise.
Return to Sport Question
Q: What are the functional criteria for return to sport after Grade II hamstring strain? A: (1) Askling H-test negative (pain-free active knee flexion with hip extension), (2) H:Q ratio greater than 0.8 (isokinetic testing - hamstring:quadriceps strength ratio), (3) Pain-free full sprinting at match speed, (4) Completed sport-specific drills without symptoms, (5) Minimum time: 4-8 weeks for Grade II (NOT 3 weeks). Premature return (within 3 weeks) leads to 34% re-injury vs 12% with adequate rehabilitation.
Australian Context and Medicolegal Considerations
Australian Football League (AFL) Data:
AFL Epidemiology
- 15-20% of all AFL injuries are hamstring injuries (most common muscle injury)
- Biceps femoris: 82% of hamstring injuries in AFL
- Average games missed: 2.7 games (range 0-15)
- Re-injury rate: 12.6% with modern protocols (down from 25%)
- Economic impact: Estimated AU$500,000 per season per club in lost player availability
AFL Return-to-Play Policies
- Mandatory minimum 21-day absence for Grade II injuries (implemented 2015)
- Functional testing required: Including H:Q ratio and Askling test
- GPS monitoring: Training load management to prevent re-injury
- Nordic hamstring programs: Mandatory in all AFL clubs (2x per week)
- These policies reduced re-injury rate from 25% to 12.6%
Australian Guidelines:
| Guideline | Recommendation | Source |
|---|---|---|
| Sports Medicine Australia | Nordic hamstrings mandatory for prevention in high-risk sports | SMA Position Statement 2019 |
| ACSQHC Surgical Safety | DVT prophylaxis for hamstring surgery (intermediate risk) | ACSQHC Guidelines 2020 |
| PBS Imaging | MRI rebates available for hamstring injury assessment | Medicare Benefits Schedule |
| WorkCover NSW | Physiotherapy coverage for work-related hamstring injuries (up to 12 weeks) | NSW Workers Compensation |
Medicolegal Considerations:
Consent and Documentation Requirements
Key documentation for hamstring surgery:
- Detailed informed consent including sciatic nerve injury risk (1-3%)
- MRI measurements documenting retraction distance and number of tendons
- Explanation of conservative alternatives and expected outcomes
- Clear documentation of functional deficit (strength testing, gait assessment)
- Post-operative protocol explained (brace compliance, weight-bearing restrictions)
- Common litigation issues: Sciatic nerve palsy (inadequate warning), re-rupture (premature return), persistent weakness (unrealistic expectations)
Australian Practice Patterns:
- Public vs Private: Most proximal hamstring repairs performed in private hospitals (limited public availability for sports injuries)
- Waiting times: Typical 2-4 weeks in private system (acceptable for acute repairs)
- Subspecialty referral: Sports medicine or orthopaedic surgeons with special interest
- Rehabilitation access: Private physiotherapy often required (public system limited sports rehab)
Workplace Considerations:
- Hamstring injuries common in manual workers (lifting, carrying)
- WorkCover typically covers physiotherapy for 12 weeks
- Return-to-work planning requires functional capacity assessment
- Modified duties often possible during rehabilitation phase
HAMSTRING INJURIES - EXAM ESSENTIALS
High-Yield Exam Summary
Key Anatomy
- •Biceps femoris long head (BFlh) = 80% of injuries (dual innervation: tibial + peroneal)
- •Three muscles: ST (most medial), BFlh (lateral), SM (deep)
- •Injury site: Proximal myotendinous junction (most common) or ischial avulsion
- •Eccentric injury at late swing phase (70-80% of gait cycle)
Grading Classification
- •Grade I: Less than 10% cross-sectional area, 2-3 weeks return
- •Grade II: 10-50% area, 4-8 weeks return (functional criteria essential)
- •Grade III: Greater than 50% or complete avulsion, surgery if greater than 2cm retraction
- •MRI essential for grading and surgical planning
Treatment Algorithm
- •Grade I-II: Conservative (RICE, Nordic hamstrings, functional criteria for return)
- •Grade III with less than 2cm: Conservative trial (may heal)
- •Grade III with greater than 2cm retraction: URGENT surgical repair (within 4 weeks)
- •Complete 3-tendon avulsion: Surgical repair regardless of retraction
Surgical Pearls
- •Prone position, transverse incision over ischial tuberosity
- •PROTECT SCIATIC NERVE (lateral border, identify early, retract laterally)
- •Horseshoe anchor pattern (5 anchors), angle medially away from nerve
- •Tension repair: Hip neutral, knee 45 degrees flexion
- •Post-op: Hip brace 60 degrees limit for 6 weeks, toe-touch 2 weeks
Complications and Prevention
- •Re-injury: 34% if returned within 3 weeks, 12% with adequate rehab
- •Sciatic nerve injury: 1-3% (post-op), most resolve spontaneously
- •Nordic hamstring exercises: 51-70% reduction in re-injury (EVIDENCE-BASED)
- •Return criteria: Askling test negative, H:Q ratio greater than 0.8, pain-free sprinting
- •Sitting pain post-op: 20-40% at 6 months (resolves in 80% by 12 months)