AAOS 2026 Guidelines: Comprehensive Anterior Cruciate Ligament (ACL) Injury Management

Introduction & Epidemiology

Anterior Cruciate Ligament (ACL) injury represents one of the most prevalent sport-related knee injuries, posing significant challenges to joint function and patient quality of life. In the United States alone, approximately 200,000 ACL injuries occur annually. These injuries are particularly common in athletic populations, frequently resulting from activities involving sudden deceleration, cutting, jumping, and landing maneuvers. While injury mechanisms can be categorized as contact or non-contact, the vast majority (approximately 70%) are attributed to non-contact mechanisms. Of critical note, the incidence of non-contact ACL injuries in female athletes participating in similar sports and activities is 2 to 8 times higher than in their male counterparts, a disparity potentially attributable to differences in anatomical alignment, biomechanics, neuromuscular control, and hormonal profiles.

The ramifications of ACL injury on knee joint function are profound, particularly for young, active patients. Without effective management, these injuries can lead to persistent knee instability, gait abnormalities, and an increased risk of secondary meniscal tears, chondral damage, and the premature onset of osteoarthritis. Consequently, optimizing diagnostic and treatment strategies for ACL injuries is paramount to restoring joint function, facilitating safe return to sport, and maintaining patients' occupational and daily living capabilities.

Any therapeutic intervention inherently carries associated risks. While non-operative management avoids surgical morbidity, patients may face risks of persistent or recurrent instability and secondary meniscal and/or chondral injuries. Surgical intervention, primarily ACL reconstruction, carries potential complications including graft re-rupture, recurrent instability, post-operative arthrofibrosis (loss of range of motion), neurovascular injury, patellofemoral pain syndrome (particularly with patellar tendon autografts), and general surgical complications such as infection and deep vein thrombosis (DVT). Furthermore, patients with a history of ACL rupture face a significantly increased risk of contralateral ACL injury.

Given the complexity of ACL injury management and the variability in patient outcomes, the American Academy of Orthopaedic Surgeons (AAOS), in collaboration with representatives from the American Orthopaedic Society for Sports Medicine, the Pediatric Orthopaedic Society of North America, the American Academy of Physical Medicine and Rehabilitation, and the American College of Emergency Physicians, published its most recent Clinical Practice Guidelines (CPG) for ACL injury in 2022. These guidelines aim to provide evidence-based recommendations for orthopedic surgeons to optimize the management of patients with ACL injuries. As we prepare for clinical practice in 2026, a thorough understanding and application of these authoritative recommendations are essential for refining diagnostic and therapeutic decision-making. The guideline development process was rigorous, involving a systematic review of over 5500 abstracts and 1100 full-text articles, culminating in eight primary recommendations and seven optional considerations, supported by 324 studies meeting stringent inclusion criteria.

Surgical Anatomy & Biomechanics

The ACL is a critical intra-articular stabilizer of the knee joint. A precise understanding of its intricate anatomy and biomechanical function is fundamental to successful surgical reconstruction.

1. Anatomy

The ACL exhibits a fan-like morphology, originating from the posterior aspect of the medial surface of the lateral femoral condyle and inserting onto the anterior intercondylar area of the tibial plateau, specifically between the anterior horn of the medial meniscus and the transverse ligament. Traditionally, the ACL has been described as comprising two primary functional bundles:

• Anteromedial Bundle (AMB): Tautest in knee flexion, primarily restricting anterior tibial translation.
• Posterolateral Bundle (PLB): Tautest in knee extension, primarily limiting anterior tibial translation and internal rotation.

However, contemporary research emphasizes that the ACL is a continuous structure rather than two distinctly separate bundles. Appreciating its complex, spiraling fiber arrangement is crucial for anatomically accurate reconstruction that replicates its natural function.

ACL Femoral and Tibial Attachment Points:

• Femoral Attachment: Located on the posterior aspect of the medial surface of the lateral femoral condyle, typically C-shaped or crescentic. Its position is generally approximately 4mm anterior to the posterior edge of the distal articular cartilage of the lateral femoral condyle and approximately 7mm superior to the intercondylar ridge of the lateral femoral condyle. Precise localization of the femoral tunnel is critical for achieving isometric or near-isometric graft placement.
• Tibial Attachment: Located in the anterior intercondylar area, anterior to the tibial spines. This attachment is broader and more diffuse than the femoral attachment.

The complex spatial orientation of the ACL fibers allows it to function as a primary restraint to anterior tibial translation across the entire range of knee motion, with secondary roles in limiting varus/valgus stress at full extension and axial rotation. The AMB resists anterior translation more predominantly in flexion, while the PLB, often considered the larger and stronger component, is crucial for rotatory stability and anterior translation near extension. The continuum model recognizes that different fiber bundles become taut at varying knee flexion angles.

2. Biomechanics

The primary biomechanical functions of the ACL include:
* Primary Restraint to Anterior Tibial Translation: This is the most recognized function, preventing the tibia from sliding forward relative to the femur.
* Secondary Restraint to Internal and External Tibial Rotation: The ACL, particularly its PLB, plays a significant role in resisting excessive internal rotation of the tibia relative to the femur. It also offers some resistance to external rotation.
* Secondary Restraint to Varus/Valgus Stress: While the collateral ligaments are primary stabilizers for varus/valgus forces, the ACL contributes secondarily, especially in full extension.
* Proprioception: The ACL contains mechanoreceptors (Ruffini endings, Pacinian corpuscles, Golgi tendon organs) that contribute to knee proprioception and neuromuscular control, providing feedback on joint position and movement. This neurosensory function is often compromised following injury and may not be fully restored with reconstruction.

Understanding these biomechanical roles informs graft placement and tensioning during reconstruction to best replicate the native ACL's kinematics and stability. The goal of ACL reconstruction is to restore normal knee kinematics, including both anterior-posterior stability and rotational stability, which is often assessed clinically via pivot shift testing. The degree of rotational instability is increasingly recognized as a critical factor influencing patient outcomes and graft survival.

Indications & Contraindications

The decision-making process for ACL injury management is multifaceted, requiring careful consideration of patient-specific factors, injury characteristics, and functional goals.

Indications for Operative Management (ACL Reconstruction)

ACL reconstruction is generally indicated for patients who:
* Experience persistent knee instability and functional limitations: Despite an adequate trial of non-operative management and rehabilitation. This is particularly true for instability during activities of daily living or sport.
* Are young, active individuals: Especially those involved in pivoting or cutting sports, where a stable knee is essential for safe return to pre-injury activity levels.
* Have concomitant injuries: Such as meniscal tears (especially repairable tears or unstable meniscal tears), collateral ligament injuries (e.g., MCL Grade III), or chondral lesions that require arthroscopic intervention and are best addressed in a stable knee environment.
* Present with significant anterior laxity: Clinically assessed by Lachman or anterior drawer tests, or quantitatively measured by arthrometric devices (e.g., KT-1000/2000).
* Exhibit a positive pivot shift test: Indicating rotational instability, which is a strong predictor of future meniscal and chondral damage if left untreated.
* Skeletally immature patients: With open physes may also be candidates, though specific physeal-sparing techniques are employed to minimize growth disturbance.

Indications for Non-Operative Management

Non-operative management, typically involving extensive physiotherapy, bracing, and activity modification, may be considered for patients who:
* Are older or have low functional demands: Not participating in pivoting or cutting sports.
* Do not experience significant knee instability: During daily activities, despite an ACL-deficient knee.
* Have an isolated ACL injury: Without significant concomitant meniscal or chondral pathology.
* Are willing and able to commit to a rigorous rehabilitation program: Focused on strengthening, neuromuscular control, and activity modification.
* Sustained a partial ACL tear: With residual stability, although the distinction between partial and complete tears can be challenging and often requires arthroscopic evaluation.

Contraindications for Operative Management

Absolute contraindications to ACL reconstruction are rare and generally include:
* Active knee infection: This must be aggressively treated and resolved before any elective knee surgery.
* Severe uncontrolled medical comorbidities: That preclude safe anesthesia and surgery (e.g., severe cardiac, pulmonary, or coagulopathy issues).
* Extensive joint degeneration (severe osteoarthritis): Where an ACL reconstruction alone would not address the primary source of pain and dysfunction; typically, these patients may be candidates for total knee arthroplasty.

Relative contraindications may include:
* Unrealistic patient expectations: Regarding return to pre-injury activity levels or surgical outcomes.
* Significant fixed knee stiffness or contracture: Which should be addressed pre-operatively.
* Obesity: Which can increase surgical risks and potentially impact rehabilitation outcomes.
* Smoking: Associated with higher complication rates (infection, wound healing) and should ideally be ceased pre-operatively.

Summary Table: Operative vs. Non-Operative Indications

Pre-Operative Planning & Patient Positioning

Thorough pre-operative planning is crucial for optimizing outcomes in ACL reconstruction, encompassing patient assessment, graft selection, and meticulous surgical setup.

1. Pre-Operative Assessment

• History and Physical Examination: Detailed history of injury mechanism, symptoms (pain, instability, locking), prior knee injuries, and activity level. Physical examination confirms ACL deficiency (Lachman, anterior drawer, pivot shift tests) and assesses for concomitant injuries (meniscal, collateral ligaments, posterolateral corner). Documentation of baseline range of motion, effusion, and quadriceps atrophy is essential.
• Imaging:
  • Plain Radiographs: Anteroposterior (AP), lateral, and patellofemoral views (e.g., Merchant's, sunrise) are obtained to rule out fractures, assess alignment (e.g., tibial slope, which can influence graft strain), and identify signs of early osteoarthritis. Stress radiographs may be utilized in complex ligamentous injuries.
  • Magnetic Resonance Imaging (MRI): Confirms ACL rupture, provides detailed assessment of meniscal and chondral status, and identifies other ligamentous or bone injuries (e.g., bone bruise of the lateral femoral condyle and posterior tibia, highly suggestive of an ACL tear). MRI also helps to determine the quality and size of potential autograft tendons.
• Graft Selection: This is a critical decision based on patient age, activity level, surgeon preference, and potential donor site morbidity.
  • Autografts:
    • Bone-Patellar Tendon-Bone (BPTB): Gold standard for many surgeons, known for rigid fixation and bone-to-bone healing. Provides excellent primary stability. Potential donor site morbidity includes anterior knee pain, patellar fracture, and patellar tendon rupture.
    • Hamstring Tendons (Semitendinosus and Gracilis, ST/G): Increasingly popular due to reduced anterior knee pain and cosmetic incision. Often quadrupled to increase strength. Potential donor site morbidity includes hamstring weakness and nerve injury. Requires soft-tissue to bone healing, which can be slower.
    • Quadriceps Tendon (QT): With or without a bone block, gaining popularity. Offers robust graft tissue with potentially less donor site morbidity than BPTB, particularly for anterior knee pain. Can be harvested with a smaller incision and has a large cross-sectional area.
  • Allografts: Derived from cadaveric donors (e.g., BPTB, Achilles, ST/G). Avoids donor site morbidity but carries risks of disease transmission (though extremely low with current processing) and slower incorporation/higher re-rupture rates in younger, active patients. May be considered for revision ACL reconstruction, multi-ligamentous injuries, or patients with lower activity demands.
• Pre-operative Physical Therapy: Often beneficial to restore full range of motion, reduce swelling, and strengthen quadriceps and hamstrings prior to surgery ("prehabilitation"). This can significantly improve post-operative recovery.

2. Patient Positioning and Surgical Setup

• Anesthesia: General or regional anesthesia (spinal/epidural) can be utilized, often combined with a local anesthetic block (e.g., femoral nerve block or adductor canal block) for post-operative pain management.
• Patient Positioning: The patient is typically positioned supine on the operating table.
  • Tourniquet: A pneumatic tourniquet is applied high on the thigh to facilitate a bloodless field, crucial for arthroscopic visualization.
  • Leg Holder: A lateral post or leg holder is typically used to stabilize the operative leg, allowing the knee to be flexed to 90 degrees or more and providing valgus/varus stress as needed. The contralateral leg is often placed in a well-padded leg holder or allowed to rest flat.
  • Preparation and Draping: The entire leg, from mid-thigh to foot, is prepped and draped in a sterile fashion. The foot is often placed in a sterile stockinette or bag to allow free manipulation.
• Arthroscopy Setup:
  • Camera and Light Source: A standard 30-degree arthroscope is typically used.
  • Fluid Management: An arthroscopic pump or gravity inflow system provides continuous irrigation to distend the joint and clear debris.
  • Video Monitor: Placed in clear view of the surgeon and assistant.
  • Instrumentation: A full complement of arthroscopic instruments (probes, shavers, graspers, punches), ACL-specific instrumentation (guides, reamers, tunnels, graft passage devices), and fixation devices should be readily available and sterile.
  • Graft Table: A separate sterile back table is prepared for graft harvesting (if autograft) and preparation.

Detailed Surgical Approach / Technique (Arthroscopic ACL Reconstruction)

This section describes a general approach for arthroscopic ACL reconstruction, noting that variations exist based on graft choice, surgeon preference, and specific patient anatomy. For clarity, we will describe a common technique using a quadrupled hamstring autograft.

1. Graft Harvest and Preparation (if autograft)

• Incision: A small (2-3 cm) vertical or oblique incision is made over the anteromedial aspect of the proximal tibia, approximately 2-3 cm distal to the tibial tubercle and medial to the tibial crest.
• Dissection: The subcutaneous tissue is incised, and the sartorius fascia is identified. The sartorius fascia is incised longitudinally to expose the semitendinosus and gracilis tendons, which lie deep to it. The pes anserinus attachments are preserved as much as possible.
• Tendon Release: The tendons are carefully separated from surrounding soft tissues using a curved clamp or finger dissection. Distal attachments are typically left intact temporarily.
• Harvesting: A specialized tendon stripper is advanced distally, carefully stripping the semitendinosus and gracilis tendons from their muscle bellies. The length of harvested tendon typically ranges from 24-28 cm, which can be quadrupled to yield a graft length of 70-80 mm.
• Graft Preparation: The harvested tendons are placed on a sterile graft preparation board. Muscle tissue is meticulously removed. The tendons are then folded, typically quadrupled, and whipstitched at both ends with strong non-absorbable suture. The graft is measured for diameter (aiming for ≥8 mm) and tensioned (e.g., 80N-100N for 10 minutes) to remove viscoelastic creep, prior to final sizing. This prepared graft is kept moist with saline.

2. Arthroscopic Diagnostic Exploration

• Portal Placement:
  • Anterolateral Portal: Standard viewing portal, typically placed just superior to the lateral meniscus and lateral to the patellar tendon.
  • Anteromedial Portal: Working portal, placed just superior to the medial meniscus and medial to the patellar tendon. Its placement should be sufficiently high to allow proper instrumentation and visualization of the femoral footprint, especially for anteromedial portal drilling techniques. Accessory medial portals may be used for specific instruments.
• Diagnostic Arthroscopy: A comprehensive survey of the entire knee joint is performed using the arthroscope. This includes:
  • Patellofemoral Joint: Assessment of cartilage, tracking, and plicae.
  • Medial Compartment: Evaluation of medial meniscus, medial collateral ligament (MCL), and articular cartilage.
  • Lateral Compartment: Evaluation of lateral meniscus, lateral collateral ligament (LCL), popliteus tendon, and articular cartilage.
  • Intercondylar Notch: Assessment of the ACL remnant, PCL, and intercondylar roof.
  • Posteromedial and Posterolateral Compartments: Often visualized via specific portals or by "figure-of-4" positioning.
• Management of Concomitant Injuries: Any meniscal tears (repair vs. partial meniscectomy), chondral lesions, or other ligamentous injuries are addressed at this stage.

3. Debridement and Notch Preparation

• ACL Remnant: The ruptured ACL remnant is typically debrided to allow clear visualization of the femoral and tibial footprints. Care is taken to preserve any peripheral remnant tissue or synovium, as it may contain neural elements or contribute to graft healing and revascularization.
• Notchplasty (if required): In cases of severe intercondylar notch impingement, a notchplasty may be performed using a shaver or burr to widen the notch and prevent graft impingement, particularly in extension. This is less frequently required with modern anatomical tunnel placement techniques.

4. Tibial Tunnel Creation

• Tibial Guide Placement: An arthroscopic tibial guide is used to determine the entry point on the anteromedial tibia and the exit point within the ACL footprint on the tibial plateau. The guide pin is typically aimed for the center of the native ACL footprint, anterior to the PCL and posterior to the anterior horn of the medial meniscus. Anatomically, this is typically located 50-55% of the anterior-posterior distance of the tibial plateau from anterior to posterior, and 40-45% of the medial-lateral distance from the medial border of the tibial spine.
• Guide Pin Drilling: A guide pin is drilled from the anteromedial tibia into the joint, exiting at the desired tibial footprint.
• Tunnel Reaming: A cannulated reamer, sized to the prepared graft diameter (e.g., 8mm), is used over the guide pin to create the tibial tunnel. The tunnel should be smooth and chamfered to prevent graft abrasion.

5. Femoral Tunnel Creation

The technique for femoral tunnel creation varies significantly:

• Transtibial Technique (TT): The femoral guide is inserted through the tibial tunnel, and the guide pin is drilled from the tibial tunnel into the lateral femoral condyle. While technically straightforward, this technique often results in a more vertical graft placement, particularly with the original "isometric" positioning, potentially compromising rotational stability. Modern TT techniques aim for a more anatomical position by optimizing tibial tunnel placement.
• Anteromedial Portal Technique (AMP): The femoral guide and reamer are passed directly through the anteromedial portal. This allows for independent placement of the femoral tunnel, facilitating a more anatomical, oblique tunnel direction that better mimics the native ACL's femoral footprint. This technique is preferred by many surgeons for its ability to restore rotational stability.
  • Placement: The femoral guide pin is typically aimed at the "over-the-top" position or slightly anterior and proximal to it, within the anatomical footprint of the ACL on the medial wall of the lateral femoral condyle. In knee flexion (typically 110-120 degrees to avoid damage to the posterior cortex), a reamer matching the graft diameter is used to create the femoral tunnel.
• Outside-In Technique (OI): A guide pin is placed from an accessory lateral incision, drilled into the femoral footprint, and then reamed. This also allows for anatomical placement and independent tunnel creation.

Regardless of the technique, careful attention must be paid to avoid posterior wall blowout and ensure sufficient bone bridge for fixation. The femoral tunnel length should be adequate to accommodate the chosen fixation device and a significant portion of the graft.

6. Graft Passage and Fixation

• Suture Passage: A suture passer (e.g., shuttle wire, nitinol wire) is advanced through the femoral tunnel, retrieved through the anteromedial portal, and then passed into the tibial tunnel and out the anteromedial tibial incision.
• Graft Passage: The lead sutures attached to the graft are tied to the shuttle wire, and the graft is carefully pulled into the joint through the tibial tunnel and then into the femoral tunnel. Care is taken to avoid impingement or abrasion of the graft during passage.
• Femoral Fixation: Once the graft is fully seated in the femoral tunnel, fixation is secured. Common methods include:
  • Suspensory Fixation (e.g., Endobutton, TightRope): A cortical button or loop is placed on the lateral femoral cortex, allowing the graft to be suspended within the femoral tunnel. This provides strong, reproducible fixation.
  • Interference Screws: Bioabsorbable or titanium screws are placed alongside the graft within the femoral tunnel to compress the graft against the tunnel walls. These are often used in conjunction with suspensory fixation or as primary fixation for BPTB grafts.
  • Cross-Pin Fixation: Pins are driven through the lateral femoral condyle, perpendicular to the graft, impinging it against the tunnel wall.
• Tibial Fixation:
  • Cyclic Tensioning: The knee is cycled through a full range of motion (e.g., 0-90 degrees) multiple times while maintaining appropriate graft tension to "seat" the graft and remove any remaining creep.
  • Tensioning and Fixation: The knee is typically positioned in 20-30 degrees of flexion, and the graft is tensioned (e.g., 60-80N for hamstring grafts). Tibial fixation is then secured. Common methods include:
    • Interference Screws: Similar to femoral fixation, placed alongside the graft in the tibial tunnel.
    • Post and Washer: Sutures from the graft are tied over a post and washer on the anteromedial tibia.
    • Staples/Sutures: Less common as primary fixation for soft tissue grafts.
    • Suspensory Fixation (e.g., Adjustable Loop Devices): Newer devices allow for adjustable tensioning and fixation at the tibia.
• Final Assessment:
  • Range of Motion: Full range of motion is confirmed, checking for any signs of graft impingement.
  • Stability: Lachman, anterior drawer, and pivot shift tests are performed to confirm restoration of stability.
  • Probe Assessment: The graft tension and position are assessed with an arthroscopic probe.
  • Irrigation and Closure: The joint is thoroughly irrigated, portals are closed with sutures or sterile strips, and the skin incisions are closed in layers. A sterile dressing and knee brace (often set to restrict extension) are applied.

Complications & Management

Despite significant advancements in ACL reconstruction techniques, complications can occur. Early identification and appropriate management are crucial for optimal patient outcomes.

1. Common Complications

• Graft Failure / Re-rupture:
  • Incidence: 2-10%, higher in young, active patients. Risk factors include graft type (allograft > autograft in young patients), tunnel malposition, inadequate tensioning, early return to sport, and revision surgery.
  • Management:
    • Initial non-operative management with rehabilitation for stable knees.
    • Revision ACL reconstruction for symptomatic instability, especially in active individuals. Requires thorough pre-operative planning, including imaging (X-rays, MRI, CT for tunnel assessment) to identify tunnel malposition, address hardware, and potentially perform a staged procedure with bone grafting if tunnels are significantly enlarged.
• Arthrofibrosis (Stiffness / Loss of Motion):
  • Incidence: 5-10%. Can range from mild loss of extension to severe global stiffness. Risk factors include delayed surgery after injury, aggressive early rehabilitation (particularly for quad strength), graft impingement, and infection.
  • Management:
    • Aggressive physical therapy, including dynamic splinting.
    • Manipulation under anesthesia (MUA) for persistent motion deficits not responding to PT.
    • Arthroscopic lysis of adhesions and debridement of impingement lesions (e.g., cyclops lesion). Rarely, open arthrolysis.
• Infection:
  • Incidence: <1% (superficial) to 0.1-0.5% (deep). Risk factors include prolonged surgery, poor surgical technique, and patient comorbidities.
  • Management:
    • Prompt intravenous antibiotics (empiric, then culture-directed).
    • Arthroscopic irrigation and debridement.
    • In severe cases, graft removal may be necessary, followed by delayed revision once infection is eradicated.
• Patellofemoral Pain Syndrome (PFPS):
  • Incidence: Up to 20-30% with BPTB autografts, less common with hamstring or quadriceps grafts. Related to donor site morbidity.
  • Management:
    • Physical therapy focusing on quadriceps strengthening, patellar mobilization, and core stability.
    • Activity modification.
    • Analgesics, NSAIDs.
    • Rarely, surgical intervention for specific identifiable causes (e.g., hardware removal, lateral retinacular release).
• Neurovascular Injury:
  • Incidence: Rare (<0.1%). Damage to saphenous nerve (sensory deficit along medial calf), peroneal nerve (foot drop), or popliteal artery/vein.
  • Management:
    • Careful surgical technique to avoid these structures.
    • For nerve injury: observation, nerve blocks, or neurolysis; rarely, nerve repair.
    • For vascular injury: immediate vascular surgery consultation and repair.
• Deep Venous Thrombosis (DVT) / Pulmonary Embolism (PE):
  • Incidence: DVT 1-5%, PE <0.1%. Risk factors include patient comorbidities (hypercoagulable states), prolonged immobility, and obesity.
  • Management:
    • Prophylaxis (early mobilization, sequential compression devices, pharmocological anticoagulation in high-risk patients).
    • Diagnosis with Doppler ultrasound (DVT) or CT pulmonary angiography (PE).
    • Anticoagulation therapy.
• Tunnel Enlargement:
  • Incidence: Variable, often asymptomatic. More common with hamstring grafts and suspensory fixation.
  • Management: Usually observed. For revision surgery, requires careful planning, possibly bone grafting, and staged procedures.
• Growth Plate Injury (in Skeletally Immature Patients):
  • Incidence: Low with physeal-sparing techniques.
  • Management:
    • Physeal-sparing techniques (e.g., all-epiphyseal, partial transphyseal).
    • Monitor for limb length discrepancy or angular deformity; epiphysiodesis or osteotomy if significant.

Table: Common Complications, Incidence, and Salvage Strategies

Post-Operative Rehabilitation Protocols

A structured and progressive rehabilitation protocol is paramount for successful ACL reconstruction outcomes. The goal is to restore full range of motion, strength, proprioception, and ultimately facilitate a safe return to sport and daily activities while protecting the healing graft. Protocols are typically phased.

Phase I: Protection and Early Motion (Weeks 0-6)

• Goals: Protect the healing graft, reduce pain and swelling, restore full passive knee extension, achieve 90-110 degrees of flexion, initiate quadriceps activation.
• Weight Bearing:
  • Often partial weight-bearing (PWB) with crutches for the first 1-2 weeks, progressing to full weight-bearing (FWB) as tolerated with a brace locked in extension.
  • Some protocols allow immediate FWB as tolerated.
• Bracing: A hinged knee brace is commonly used, locked in extension for ambulation initially. It can be unlocked for controlled range of motion exercises.
• Range of Motion (ROM):
  • Week 0-2: Focus on achieving full passive extension (critical for preventing arthrofibrosis) and flexion to 90 degrees.
  • Week 2-4: Progress flexion to 110-120 degrees.
  • Exercises: Heel slides, prone hangs (for extension), gentle continuous passive motion (CPM) machine (optional), stationary bike (no resistance) to encourage motion.
• Strength:
  • Quadriceps: Quad sets, straight leg raises (SLRs) in various planes (no resistance initially), neuromuscular electrical stimulation (NMES) for quad activation. Avoid isolated open-chain terminal knee extension (0-30 degrees) for the first 6-12 weeks due to increased anterior tibial shear forces.
  • Hamstrings: Gentle hamstring curls (if non-hamstring graft) or isometric holds (if hamstring graft).
  • Calf: Ankle pumps, calf raises.
• Other: Cryotherapy, elevation, compression for swelling control. Patellar mobilizations.

Phase II: Strength and Neuromuscular Control (Weeks 6-16)

• Goals: Normalize gait, achieve full functional range of motion, improve quadriceps and hamstring strength, begin proprioceptive training, restore neuromuscular control.
• Weight Bearing: Wean off crutches and brace as stability, strength, and confidence improve. Brace may be used for higher-risk activities.
• ROM: Achieve full pain-free ROM.
• Strength:
  • Closed Chain Exercises: Wall squats, leg press, lunges, step-ups/downs. Gradually increase resistance.
  • Open Chain Exercises: Begin cautiously after 10-12 weeks, focusing on controlled motion and avoiding excessive anterior shear. Hamstring curls, leg extensions (avoiding terminal knee extension initially).
  • Core Strengthening: Plank, side plank, bird-dog exercises.
• Neuromuscular Control/Proprioception:
  • Balance exercises: single-leg stance, wobble board, foam pad.
  • Agility drills: cone drills (walking/jogging initially).
• Cardiovascular: Stationary bike with resistance, elliptical trainer, swimming (kickboard optional).

Phase III: Return to Activity / Sport-Specific Training (Weeks 16-24+)

• Goals: Maximize strength, power, agility, and endurance. Prepare for safe return to sport through sport-specific drills.
• Strength: Continue progressive resistance exercises. Incorporate plyometrics (box jumps, hopping, bounding) once strength and control are adequate. Focus on eccentric control.
• Agility & Sport-Specific Drills:
  • Ladder drills, shuttle runs, cutting drills, jumping, landing mechanics training.
  • Gradual progression to sport-specific activities (e.g., throwing, hitting, non-contact drills).
• Endurance: Running progression, interval training.
• Return to Sport Criteria (Typically 9-12 months post-op, minimum 6 months):
  • Clinical: No pain, no effusion, full ROM, no instability on clinical exam.
  • Strength: Quadriceps and hamstring strength symmetrical to contralateral limb (isokinetic testing, >90% Limb Symmetry Index).
  • Functional: Passing a battery of functional tests (e.g., single-leg hop test battery, T-test, agility drills) with >90% Limb Symmetry Index.
  • Psychological Readiness: Patient confidence and readiness for return to sport (e.g., using questionnaires like ACL-RSI).
  • Surgeon's Clearance: Final decision based on all criteria and individual patient factors.

Considerations for Rehabilitation

• Individualization: Protocols must be tailored to the individual patient's progress, graft type, concomitant injuries, and specific goals.
• Graft Healing: The biological process of graft ligamentization takes 12-24 months. While mechanical stability is restored surgically, biological maturation is ongoing.
• Neuroplasticity: Addressing neuromuscular deficits and improving motor control is as important as restoring strength.
• Prevention: Emphasize long-term injury prevention strategies, particularly for contralateral ACL tears.

Summary of Key Literature / Guidelines

The 2022 AAOS Clinical Practice Guidelines (CPG) for Anterior Cruciate Ligament Injury are the current authoritative resource guiding management in the United States and are pivotal for informing practice in 2026. These guidelines supersede previous iterations and reflect a comprehensive, evidence-based consensus among leading orthopedic and sports medicine societies.

The guideline development process was rigorous, involving a systematic review of over 5500 abstracts and 1100 full-text articles, culminating in eight primary recommendations and seven optional considerations, supported by 324 high-quality studies. While a detailed review of each recommendation is beyond the scope of this summary, the overarching themes and key takeaways include:

1. Timing of Surgery: The guidelines acknowledge the evolving evidence regarding the optimal timing of ACL reconstruction. While immediate surgery may be considered for select cases, waiting until knee swelling has subsided and full range of motion (especially extension) has been achieved pre-operatively is generally preferred to minimize the risk of post-operative arthrofibrosis. For skeletally immature patients, physeal-sparing techniques are recommended, or delaying surgery until closer to skeletal maturity, when appropriate.
2. Graft Choice: The CPG evaluates the evidence for various autograft and allograft options. While specific recommendations may vary, the general consensus reinforces the efficacy of autografts (BPTB, hamstring, quadriceps tendon) for young, active patients due to lower re-rupture rates compared to allografts. Allografts may be considered in revision settings, multi-ligament injuries, or in older, less active individuals. The guidelines do not definitively endorse one autograft type over others, recognizing comparable outcomes when appropriately indicated and executed.
3. Surgical Technique: Emphasis is placed on anatomical tunnel placement to restore both anterior-posterior and rotational stability. Techniques that allow for independent femoral tunnel placement (e.g., anteromedial portal or outside-in) are often favored over traditional transtibial approaches, especially for younger patients or those with high-demand functional expectations. The guidelines support the use of robust fixation methods tailored to the chosen graft type.
4. Concomitant Injuries: The guidelines stress the importance of thoroughly assessing and addressing concomitant meniscal and chondral injuries during ACL reconstruction, as these significantly impact long-term knee health and rehabilitation. Meniscal repair, when feasible, is generally advocated to preserve meniscal tissue and mitigate the risk of future osteoarthritis.
5. Rehabilitation: A structured and progressive rehabilitation program is strongly recommended, starting pre-operatively (prehabilitation) and continuing meticulously post-operatively. Key principles include:
   • Early restoration of full passive knee extension.
   • Progressive weight-bearing and range of motion.
   • Emphasis on quadriceps and hamstring strengthening, with cautious progression of open-chain kinetic exercises.
   • Integration of neuromuscular control and proprioceptive training.
   • Gradual return to sport-specific activities, typically not before 9-12 months post-operation, contingent on objective functional testing and psychological readiness, not solely time-based milestones.
6. Prevention: The CPG highlights the persistent risk of contralateral and ipsilateral re-rupture and underscores the importance of secondary prevention programs, particularly for female athletes, focusing on neuromuscular training and biomechanical correction.

In conclusion, the AAOS 2022 CPG provides a robust, evidence-based framework for the comprehensive management of ACL injuries. Integrating these recommendations into clinical practice is essential for optimizing diagnostic accuracy, refining surgical techniques, guiding rehabilitation strategies, and ultimately improving long-term outcomes for patients suffering from ACL disruptions. Continuous engagement with evolving literature and adherence to these guidelines represent the cornerstone of expert orthopedic care.