ACL Reconstruction — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

ACL reconstruction is an arthroscopic surgical procedure to replace a completely torn anterior cruciate ligament (ACL) with a tendon graft taken from the patient's own body or from a donor. The ACL is one of four major knee ligaments and the primary restraint against anterior tibial translation and rotational instability. When ruptured — most commonly during pivoting sports such as football, basketball, and skiing — it rarely heals on its own. ACL reconstruction is one of the most frequently performed orthopaedic procedures worldwide, with approximately 200,000 surgeries performed in the United States annually. The procedure is performed by orthopaedic surgeons using arthroscopic techniques through 2–3 small portal incisions, visualising the joint on a high-definition monitor. The torn remnant is removed and replaced by a graft threaded through precisely drilled bone tunnels in the femur and tibia. The graft undergoes a biological process called ligamentisation over 12–18 months, gradually acquiring the mechanical properties of a native ACL. ACL reconstruction is performed exclusively by fellowship-trained orthopaedic surgeons specialising in sports medicine or knee surgery. The procedure was first standardised in the 1970s using open techniques; arthroscopic reconstruction became the gold standard through the 1990s and is now universally adopted. Recovery milestones and return-to-sport criteria continue to be refined, with current evidence supporting criteria-based rather than time-based return to competition.

ACL reconstruction is indicated for patients with a complete ACL rupture confirmed on MRI who experience knee instability and wish to return to pivoting or cutting sports. The procedure is typically recommended for active individuals aged 15–50, though age alone is not a contraindication. Key selection criteria include complete ACL tear with functional instability, failed conservative management (physiotherapy) for 3–6 months in lower-demand patients, concurrent repairable meniscal tears (addressed at the same surgery), and a desire to return to sport or physically demanding work. In younger adolescents with open growth plates, physeal-sparing reconstruction techniques are used to avoid growth disturbance. Older or less active patients with partial tears or isolated ACL deficiency without instability may be managed non-operatively with physiotherapy focused on quadriceps and hamstring strengthening. MRI confirmation of complete rupture and a Lachman test or pivot-shift examination documenting instability are required before surgery is planned.

ACL reconstruction is performed under general or spinal anaesthesia with the patient supine and a tourniquet on the thigh. Under arthroscopic guidance, the surgeon first inspects the entire knee joint, addresses any meniscal tears (repair or partial meniscectomy), and removes the ACL remnant from the intercondylar notch. Graft options include the hamstring tendon (gracilis and semitendinosus, harvested through a 3 cm anteromedial incision), the bone–patellar tendon–bone (BPTB) graft (harvested from the front of the knee), or an allograft (donor tendon). Bone tunnels are drilled in the anatomical ACL footprint positions in the femur and tibia using calibrated reamers. The graft is then pulled through the tunnels with sutures and fixed at each end using bioabsorbable screws, cortical buttons, or cross-pins depending on graft type and surgeon preference. Graft tension and knee stability are confirmed under arthroscopic and fluoroscopic guidance before wound closure. The entire procedure takes 60–90 minutes. A local anaesthetic nerve block is often used for postoperative pain control. After securing graft fixation, the joint is irrigated copiously with saline, portals are closed with absorbable sutures, and dressings applied. A cryotherapy device or ice pack is placed immediately to reduce post-operative swelling. The patient is transferred to recovery and physiotherapy begins within 24 hours.

ACL reconstruction delivers excellent functional outcomes, with over 90% of patients returning to their pre-injury sport at the same or higher level. Graft survival rates exceed 85% at 10 years in appropriately selected patients. Hamstring and BPTB grafts achieve comparable long-term stability and functional scores (IKDC, Lysholm scale). The procedure eliminates the recurrent giving-way episodes that lead to secondary meniscal and cartilage injuries, reducing the long-term risk of post-traumatic osteoarthritis. Return to jogging is expected at 3–4 months; return to competitive sport at 6–9 months following completion of structured neuromuscular rehabilitation. Comprehensive physiotherapy incorporating progressive strength training, proprioception retraining, and sport-specific conditioning is the single most important factor in achieving optimal outcomes. Quality of life improvements are substantial — patients report significant gains in knee function, confidence, and activity levels post-reconstruction. The AAOS Clinical Practice Guideline (2022) recommends ACL reconstruction combined with rehabilitation for patients seeking to return to high-demand sport.

The overall complication rate for ACL reconstruction is low, but relevant risks must be understood. Graft failure (re-rupture) occurs in 5–10% of cases and is more common with early return to sport, poor neuromuscular control, and in adolescent patients. Tunnel malposition leading to impingement or laxity is an avoidable technical complication. Deep vein thrombosis occurs in less than 1% with appropriate prophylaxis. Infection (septic arthritis) is rare (<0.5%) but requires urgent washout. Anterior knee pain and patellar tendon donor-site morbidity are more common after BPTB harvest. Stiffness (arthrofibrosis) may develop if rehabilitation is not commenced promptly post-surgery. Neurovascular injury and compartment syndrome are extremely rare. The contralateral knee re-rupture rate in athletes is approximately 15–20% within two years of return to sport, making bilateral limb rehabilitation important. Females have a 2–6 times higher ACL re-injury risk than males due to biomechanical and hormonal factors; preventive neuromuscular training programmes (e.g., FIFA 11+) reduce re-injury risk by up to 50%.

Most patients are discharged the same day or after one night. A knee brace may be provided for comfort in the first 2 weeks, though evidence for its necessity is limited. Crutches are used for 2–4 weeks until the quadriceps achieve sufficient control for a normal gait pattern. Physiotherapy begins within 3–5 days of surgery focusing on reducing swelling, regaining full extension, and activating the quadriceps. Progressive rehabilitation milestones include: full weight-bearing at 2 weeks; stationary cycling at 6–8 weeks; jogging at 12–16 weeks; lateral movements and agility at 4–5 months; and return to unrestricted sport at 6–9 months (or later when criteria-based testing demonstrates readiness). Return-to-sport decisions should be based on limb symmetry index (LSI) for quad/hamstring strength (>90%), hop testing, and psychological readiness rather than time alone. Patients should avoid contact sport until LSI criteria are met. Complete ligamentisation of the graft requires 12–18 months, making ongoing vigilance essential even after return to sport.