What is the standard protocol for ACL (Anterior Cruciate Ligament) rehabilitation?

ACL Rehabilitation Protocol

ACL rehabilitation should follow a criterion-based progression over 9-12 months, combining strength and motor control training with objective milestones rather than relying solely on time-based advancement. 1

Core Rehabilitation Principles

Strength and motor control training must be combined throughout rehabilitation—one cannot replace the other. 1 The protocol should be criterion-based with time considered necessary but not sufficient for progression unless coupled with objective physical and psychological criteria. 1

Preoperative Phase

• At least one preoperative visit is recommended to ensure adequate voluntary quadriceps activation and no flexion contracture. 1
• Measure preoperative range of motion (ROM), as extension deficits are major risk factors for postoperative extension deficits. 1
• Assess quadriceps strength, as preoperative deficits >20% negatively impact 2-year outcomes. 1
• Preoperative rehabilitation improves postoperative quadriceps strength, knee ROM, and may decrease time to return to sport. 1

Early Postoperative Phase (Weeks 0-4)

Immediate Management

Early accelerated rehabilitation with joint mobilization and weight-bearing within 3 days should be the mainstream approach for isolated ACL surgeries. 1 When concomitant injuries (meniscal, cartilage) are present, adapt the early phase according to surgeon instructions. 1

Weight Bearing & Mobility

• Immediate weight bearing is safe and reduces anterior knee pain, but only if correct gait pattern is maintained (with crutches if necessary) without pain, effusion, or temperature increase. 1
• Full extension ROM should be achieved immediately. 1

Pain Management

• Cryotherapy can be applied in the first postoperative week to reduce pain (effective up to 1 week post-surgery). 1
• Physical therapy modalities may be beneficial as adjuncts when pain is present, though evidence is conflicting and cost/time may outweigh benefits. 1

Quadriceps Reactivation

• Start isometric quadriceps exercises in the first week when pain-free, including static contractions and straight leg raises. 1, 2
• Electrostimulation can be added to isometric training during the first postoperative weeks to re-educate voluntary quadriceps contraction. 1

Progressive Strengthening (Weeks 2-8)

Closed kinetic chain (CKC) exercises can begin at week 2 postoperative. 1, 2

Open kinetic chain (OKC) exercises have graft-specific protocols:

• For bone-patellar tendon-bone (BPTB) grafts: Start OKC at week 4 in restricted ROM (90°-45°) with extra resistance allowed. 1, 2
• For hamstring (HS) grafts: Start OKC at week 4 in restricted ROM (90°-45°) but add no extra weight for first 12 weeks to prevent graft elongation. 1

ROM progression for OKC exercises: 1, 2

• Week 4: 90°-45°
• Week 5: 90°-30°
• Week 6: 90°-20°
• Week 7: 90°-10°
• Week 8: Full ROM

Important caveat: OKC exercises may induce more anterior knee pain in BPTB patients compared to CKC exercises. 2 Monitor for pain and effusion—if present, do not progress. 1

Intermediate Phase (Months 2-4)

Neuromuscular Training

Neuromuscular (motor control) training must be added to strength training—it cannot be replaced by strength training alone. 1 This includes balance, proprioception, and movement quality work. 1

• Altered neuromuscular function and biomechanics after ACLR are risk factors for second ACL injury. 1
• Focus on correct movement quality to prevent reinjuries. 1

Core Stability

Core stability exercises should be added to improve gait, subjective knee function, and ROM. 1 A 4-6 week core stability program can be integrated during this phase. 1

Aquatic Therapy

Aquatic therapy may be initiated at 3-4 weeks postoperative (once wound completely healed) to improve subjective knee function during the early phase. 1

Psychological Assessment

Evaluate psychological factors using objective instruments throughout rehabilitation. 1 Self-efficacy, locus of control, and fear of reinjury significantly influence rehabilitation progress and return to play. 1

Advanced Phase (Months 4-9)

Plyometric and Agility Training

Plyometric and agility training should be added at the advanced phase to improve subjective function and functional activities without increasing laxity or pain. 1

• The combination of plyometric and eccentric training is more effective than either alone for improving balance, functional activities, and subjective knee function. 1, 2
• Both low-intensity and high-intensity plyometric programs (8 weeks) improve knee function and psychosocial status. 1

Running Progression

Return to running requires a combination of time-based, clinical, and functional criteria. 1

Minimum criteria before initiating running: 1

• Full knee flexion ROM
• Full extension ROM
• No effusion or trace effusion only
• Limb symmetry index (LSI) >80% for quadriceps strength
• LSI >80% eccentric impulse during countermovement jump
• Pain-free aqua jogging and Alter-G running
• Pain-free repeated single-leg hopping ('pogos')

Most studies propose a minimum timeframe of 12 weeks, though some suggest 8-16 weeks. 1 There is no conclusive evidence whether return to running before 12 weeks is safe. 1

Driving

• Right-sided ACLR: Brake response time normalizes at approximately 4-6 weeks. 1
• Left-sided ACLR: Brake response time normalizes at approximately 2-3 weeks. 1

Return to Sport Phase (Months 9-12)

Comprehensive Testing Battery

An extensive test battery for quantity and quality of movement is required—no single test has validated predictive value. 1

Minimum criteria for return to sport clearance: 1

Clinical Assessment:

• No pain or swelling
• Full knee ROM
• Stable knee (negative pivot shift, Lachman, instrumented laxity evaluation)

Patient-Reported Outcomes:

• Normalized subjective knee function using IKDC
• Psychological readiness using ACL-RSI scale
• Low kinesiophobia using Tampa Scale

Strength Testing:

• Isokinetic quadriceps and hamstring peak torque at 60°/s should display 100% symmetry for high-demand pivoting sports. 1
• Restore preoperative absolute values (if available) and normative values for sport/activity level. 1
• For pivoting/contact sports, LSI of 100% is recommended; for other sports, LSI >90% may be acceptable. 1, 2

Functional Testing:

• Countermovement jump and drop jump >90% symmetry of jump height and concentric/eccentric impulse. 1
• Reactive strength index (height/time) >1.3 for double leg and >0.5 for single leg for field sport athletes. 1
• Hop test battery with LSI >90-100%. 1

Biomechanical Assessment:

• Normalize absolute and symmetry values for moments, angles, and work in vertical/horizontal jumps (sagittal and frontal plane at hip, knee, ankle). 1
• Restore >90% symmetry of vertical ground reaction forces and knee biomechanics during high-speed running and change of direction. 1

Sports-Specific Training:

• Complete a sports-specific training programme before clearance. 1
• Psychological factors, particularly fear of reinjury, are the most significant contributors to not returning to sport—inadequate sports-specific exposure may contribute. 1

Return to Competition

Completion of rehabilitation and clearance to return to sport is NOT the same as return to competition. 1 There should be a transition phase from sports participation to sports performance with progressive and controlled exposure to the athlete's sport before unrestricted competition. 1

Supervision Considerations

Unsupervised rehabilitation may be appropriate for patients who cannot afford supervised care, have poor access to physiotherapy, or have high motivation and compliance. 1 However, all patients should have periodic supervised assessments to ensure proper progression. 1

Common Pitfalls

• Avoid time-based progression alone—always couple time criteria with objective physical and psychological measures. 1
• Monitor for effusion and pain—these indicate excessive stress and require modification before progression. 1
• Do not neglect psychological assessment—fear of reinjury is the primary barrier to return to sport. 1
• Ensure adequate sports-specific training—insufficient exposure contributes to poor return-to-sport rates. 1
• For BPTB grafts, monitor anterior knee pain closely as it may indicate excessive patellar tendon strain. 2