What is a Hamstring Graft?

The hamstring autograft uses tendons from the back of your thigh—typically the semitendinosus and sometimes the gracilis tendons. These are harvested through a small incision on the inner (medial) side of your upper shin.

Key Characteristics

  • Graft Source: Semitendinosus ± gracilis tendons
  • Configuration: Folded 4-strand (quadrupled) graft
  • Fixation: Soft tissue to bone (suspensory or interference)
  • Strength: Quadrupled graft ~250% of native ACL

Why Surgeons Choose Hamstring Grafts

The hamstring graft has become the most common choice globally because:

  • Less anterior knee pain: No disruption of the extensor mechanism
  • Smaller incision: Less visible scarring
  • Strong graft: When quadrupled, very strong construct
  • Kneeling comfort: Better tolerance for kneeling activities
  • Versatile: Good option for most activity levels

Advantages & Disadvantages

✓ Advantages

  • Less anterior knee pain than BTB
  • Better kneeling tolerance
  • Smaller incision and scar
  • Strong quadrupled graft
  • Lower risk of patella fracture
  • Hamstrings regenerate over time

✗ Disadvantages

  • Hamstring weakness (temporary to long-term)
  • Soft tissue-to-bone healing (slower)
  • Variable graft size based on anatomy
  • Slightly higher re-rupture rates in some studies
  • Potential hamstring cramping
  • Medial knee pain at harvest site

Recovery Timeline

Hamstring grafts have a soft tissue healing timeline that differs from bone-to-bone grafts:

Week 0-2

Protection Phase

  • Brace locked at 0° for walking
  • Weight bearing as tolerated
  • Swelling and pain management
  • Quad sets, ankle pumps, gentle ROM
  • Protect hamstrings (no active flexion against resistance)
Week 2-6

Early Rehab

  • Progress ROM: Goal of 90° by week 4, full by week 6
  • Full extension is priority (0° or slight hyperextension)
  • Wean off crutches (week 2-4 typically)
  • Continue hamstring protection
  • Stationary bike when ROM allows
Week 6-12

Strengthening Phase

  • Full ROM expected
  • Begin gentle hamstring strengthening
  • Progressive quad and hip strengthening
  • Pool exercises and low-impact cardio
  • Balance and proprioception work
Month 3-6

Advanced Strengthening

  • Running typically begins ~4-5 months
  • Progressive hamstring loading (key focus)
  • Single-leg exercises
  • Quad and hamstring LSI goals: 70%+
Month 6-9

Return to Sport Prep

  • Agility and cutting drills
  • Plyometrics and sport-specific training
  • Strength goals: 85-90% LSI
  • Hop test progression
  • Address any persistent hamstring deficits
Month 9-12+

Return to Sport

  • Meet all return-to-sport criteria
  • Quad AND hamstring LSI >90%
  • Hop tests >90%
  • Psychological readiness (ACL-RSI >65)
  • Sport-specific clearance testing

Hamstring Graft-Specific Considerations

⚠️ Hamstring Weakness Management

The most important consideration with hamstring grafts is addressing donor site weakness. Research shows persistent hamstring deficits are common if not specifically addressed:

  • Protection early: No resisted hamstring curls for 6-8 weeks
  • Progressive loading: Gradual reintroduction of hamstring exercises
  • Hip extension focus: Work hamstrings in lengthened positions
  • Nordic curls: Important for eccentric strength (later stages)
  • Test hamstring strength: As important as testing quads

Do Hamstrings Regenerate?

Research shows the semitendinosus (and gracilis if harvested) tendons do regenerate:

  • New tendon tissue forms in most patients (70-100%)
  • Regeneration begins within weeks and continues for 1-2 years
  • New tissue may attach lower on the tibia than original
  • Strength recovery depends on rehab, not just regeneration
  • Some persistent weakness is common even with regeneration

Protecting the Harvest Site

The medial knee/upper shin area needs time to heal:

  • Tenderness and bruising are normal for several weeks
  • Avoid aggressive hamstring stretching early on
  • Some numbness on the inner shin is common (nerve branches)
  • Cramping during hamstring activation can occur

Deep Knee Flexion

Unlike BTB grafts, hamstring grafts typically allow comfortable deep knee flexion once healed. Full squats and kneeling are generally well-tolerated.

Key Exercises for Hamstring Graft Recovery

Early Phase (Weeks 0-6)

Quad Sets Essential for quad activation Heel Slides ROM restoration Straight Leg Raises All planes Prone Hangs Extension recovery

Note: Avoid resisted hamstring curls during this phase.

Strengthening Phase (Weeks 6-12)

Bridges Begin gentle hamstring activation Mini Squats Double leg, progress depth Step-Ups Low step, control descent Leg Press Light resistance

Hamstring Focus Phase (3+ Months)

Romanian Deadlifts Key for hamstring lengthening Single Leg Bridges Progress to single leg Slider Curls Eccentric hamstring work Nordic Curls Advanced (6+ months)

Return to Sport Phase (6+ Months)

Single Leg Deadlifts Balance and posterior chain Kettlebell Swings Hip hinge power Sprinting Progression Hamstrings work hard during sprinting Agility Drills Multi-directional movement

What the Research Says

Outcomes Compared to BTB

Large studies show similar long-term outcomes between hamstring and BTB grafts. Some meta-analyses suggest slightly higher re-rupture rates with hamstring grafts in young athletes, while others show no difference. Both are considered excellent options.

Hamstring Strength Deficits

Studies consistently show hamstring strength deficits persist if not specifically rehabilitated. Deficits of 10-20% are common at 2 years post-op without targeted hamstring work. Dedicated hamstring strengthening can minimize this.

Tendon Regeneration

MRI studies show semitendinosus regeneration in 70-100% of patients, though the new tendon often attaches more distally. Functional strength recovery requires specific rehabilitation regardless of anatomical regeneration.

Anterior Knee Pain

Multiple studies confirm significantly lower rates of anterior knee pain and kneeling discomfort compared to BTB grafts (5-10% vs 15-25%).

Frequently Asked Questions

Will my hamstrings be weak forever?

Not necessarily. While some degree of hamstring weakness is common, dedicated rehabilitation can restore most function. The key is specifically targeting hamstring strengthening throughout recovery, not just focusing on quads.

Why does my hamstring cramp?

Cramping is common in the first few months, especially with hamstring activation. This typically resolves as the muscle adapts. Stay hydrated, progress exercises gradually, and gentle stretching may help.

Can I do deep squats?

Yes, hamstring grafts generally allow excellent deep flexion once healed. Most patients can squat deeply and kneel comfortably. Progress to full depth gradually as strength improves.

Will I be able to sprint again?

Yes, most patients return to full sprinting. However, sprinting places high demands on hamstrings, so building strength before high-speed running is essential. Your hamstrings need to be strong enough to handle the eccentric demands of sprinting.

Is my graft weaker than a BTB graft?

When properly constructed, a quadrupled hamstring graft is actually stronger than a BTB graft in terms of ultimate tensile strength. The key is adequate graft thickness and proper rehabilitation.

Track Your Recovery

Use our tools to monitor your progress and psychological readiness:

ACL-RSI Assessment Return-to-Sport Checklist