What is the recommended physical therapy protocol for an adult with an anterior cruciate ligament (ACL) tear, including both operative and non‑operative management and tailored to the patient’s age, activity level, and associated injuries?

Physical Therapy Protocol for ACL Tear

The optimal physical therapy approach for ACL tears depends critically on patient age, activity level, and surgical versus non-surgical management, with supervised rehabilitation programs forming the cornerstone of both pathways. 1

Initial Assessment and Decision-Making

For young, active patients (<30 years) participating in cutting and pivoting sports, ACL reconstruction with pre- and post-operative rehabilitation is the appropriate treatment to prevent future meniscal and cartilage damage. 1, 2 The AAOS rates ACL reconstruction with autograft as "Appropriate" (score 8/9) for this population. 1

For older, less active patients without significant instability, activity modification combined with supervised rehabilitation is appropriate initial management. 1 Self-directed exercise programs and functional bracing receive only "May Be Appropriate" ratings (score 6/9) due to insufficient evidence for return to high-demand activities. 1

Non-Operative Rehabilitation Protocol

Phase 1: Acute Phase (Weeks 0-2)

• Immediate initiation of supervised physical therapy focusing on pain and swelling control 3
• Quadriceps strengthening exercises to prevent atrophy 3, 4
• Range of motion restoration to achieve full extension and progressive flexion 5
• Aspiration of tense, painful effusions may be considered for symptom relief 1

Phase 2: Strengthening Phase (Weeks 2-12)

• Progressive quadriceps strengthening using both open and closed kinetic chain exercises 4, 5
• Balance and proprioception training to improve neuromuscular control 3, 5
• Functional exercises targeting knee stability during daily activities 3
• Strict activity modification avoiding pivoting and contact sports during this 3-month trial period 2, 3

Phase 3: Return to Activity (After 3 Months)

• Serial clinical examinations using the Lachman test to assess ACL integrity and detect progression 2, 3
• Functional evaluation including hop testing to determine readiness for sport return 1
• If functional instability develops despite adequate rehabilitation, refer for surgical consultation 3

Critical pitfall: Delaying surgery beyond 3 months when surgical intervention is indicated increases the risk of secondary meniscal and cartilage injuries. 2, 4

Post-Operative Rehabilitation Protocol

Accelerated Protocol Principles

An accelerated rehabilitation protocol without routine postoperative bracing is recommended, as it provides faster recovery without compromising stability. 5 Functional knee braces are not recommended for routine use after isolated primary ACL reconstruction as they confer no clinical benefit. 1

Phase 1: Immediate Post-Operative (Weeks 0-2)

• Pain, swelling, and inflammation control as primary objectives 5
• Immediate range of motion exercises targeting full extension and progressive flexion 5
• Early quadriceps activation and strengthening to prevent muscle atrophy 4, 5
• Weight-bearing progression as tolerated based on graft type and concomitant injuries 6

Phase 2: Early Strengthening (Weeks 2-6)

• Progressive closed kinetic chain exercises for quadriceps and hamstring strengthening 4, 5
• Gait re-education to normalize walking pattern 5
• Proprioception and balance training initiation 5

Phase 3: Advanced Strengthening (Weeks 6-12)

• Combination of strength training and motor control exercises 3, 4
• Progressive neuromuscular control training 5
• Sport-specific movement patterns without full intensity 5

Phase 4: Return to Sport Preparation (Months 3-6+)

• Criteria-based progression using objective physical and psychological measures, not time alone 4
• Functional hop testing as one factor to determine return to sport readiness 1
• Quadriceps strength recovery to near-symmetrical levels 7, 5
• Sport-specific training at increasing intensity levels 5

Special Considerations

Combined ACL and Meniscal Injuries

When meniscal repair is performed, the initial rehabilitation phase must be adapted according to surgeon instructions, typically with more conservative weight-bearing and range of motion restrictions. 4 Meniscal repair should be prioritized over meniscectomy when technically feasible, as partial meniscectomy increases osteoarthritis risk (OR 1.87) and total meniscectomy even more so (OR 3.14). 2, 4

Combined ACL and MCL Injuries

The MCL injury can be treated non-surgically with good outcomes, allowing focus on ACL management. 1

Graft-Specific Modifications

Patellar tendon grafts may require additional focus on anterior knee pain management and kneeling tolerance. 4 Hamstring grafts necessitate careful hamstring strengthening progression. 4

Monitoring and Progression

Supervised rehabilitation is superior to self-directed programs, though less intensive supervised programs may be viable for patients with limited access to physical therapy. 4 Patient adherence is a major challenge and expectations should be discussed ideally before surgery. 4

Common pitfall: Progression based solely on time rather than objective criteria increases re-injury risk. 4 Use criterion-based advancement incorporating strength, range of motion, and functional performance measures. 4, 5

Long-Term Considerations

Weight control and continued quadriceps strengthening are essential modifiable factors to slow osteoarthritis progression, which remains elevated regardless of treatment approach. 3, 4 Patients with ACL tears have increased risk of contralateral ACL injury requiring ongoing injury prevention strategies. 1