Knee Physiotherapy After ACL Surgery: Complete Guide

Phase 1: Protection and Early Motion (Weeks 0-2)

The first two weeks focus on protecting the graft, managing swelling, and restoring basic knee motion. Goals include achieving full extension equal to the other knee, reaching at least 90 degrees of flexion, and regaining quadriceps activation. You will use crutches and likely a hinged knee brace locked in extension for walking.

• Quad sets: pressing the knee flat against the bed
• Straight leg raises in all four directions
• Heel slides for flexion range of motion
• Ankle pumps for circulation
• Gentle patella mobilization

Full knee extension is the single most important goal in this phase — failure to achieve it early often leads to a permanent extension deficit that significantly impacts function.

Phase 2: Early Strengthening (Weeks 2-6)

The focus shifts to restoring range of motion beyond 90 degrees, improving quadriceps strength, and normalizing gait. Crutches are weaned off as tolerated. Goals include at least 120 degrees of flexion by week 6, walking without a limp, and performing a straight leg raise without extension lag. Exercises include stationary cycling, leg press (limited range), step-ups, and balance board exercises. Avoid open-chain knee extensions during this phase.

Phase 3: Progressive Strengthening (Weeks 6-12)

This phase emphasizes building strength and endurance while the graft matures. Goals include full range of motion, significantly improved quadriceps and hamstring strength, and normal walking on all surfaces. Exercises advance to squats, lunges, hamstring curls, calf raises, and full-range leg press. Proprioception and balance training become increasingly important — single-leg stance, wobble board exercises, and eyes-closed challenges retrain neuromuscular control.

Phase 4: Advanced Strengthening (Months 3-6)

At 3-6 months, the graft undergoes ligamentization — transforming from tendon into functional ligament tissue. The graft is actually at its weakest during this period. Goals include quadriceps strength at least 70% of the uninvolved leg and initiation of straight-line running (typically around 4-5 months if criteria are met). Running criteria require at least 70% quadriceps strength symmetry, no swelling, full range of motion, and satisfactory single-leg hop performance.

• Progressive plyometrics (double-leg before single-leg)
• Agility ladder drills at low intensity
• Sport-specific movement patterns
• Heavy strength training with squats, deadlifts, and leg press

Phase 5: Return to Sport (Months 6-12)

The final phase focuses on sport-specific fitness and passing return-to-sport criteria: quadriceps strength at least 90% of the uninvolved side, successful hop test battery (all within 90% of the other leg), functional movement screening, and psychological readiness. Evidence strongly suggests that waiting at least 9 months before returning to pivoting sports reduces re-injury risk by up to 50% for each month of delay up to 9 months.

Key Takeaways

• Full knee extension is the most critical early goal — prioritize it from day one
• ACL rehabilitation takes 9-12 months with five distinct phases
• The graft is weakest at 3-6 months during ligamentization — do not rush
• Progression is criteria-based, not time-based — meet milestones before advancing
• Return-to-sport requires passing objective testing including strength symmetry and hop tests
• Each month of delay before return to sport (up to 9 months) reduces re-injury risk

Frequently Asked Questions