An anterior cruciate ligament (ACL) tear is a partial or complete rupture of the central knee ligament that stabilizes the tibia against forward translation and rotation on the femur. ACL injury is the most common ligamentous knee injury in athletes, with an annual US incidence of approximately 69 per 100,000 person-years and 200,000-250,000 cases each year, with peak risk between ages 15 and 25.
An ACL tear (ICD-10: S83.5) is partial or complete disruption of the anterior cruciate ligament, the dominant restraint to anterior tibial translation and rotational instability of the knee. The ACL is an intra-articular ligament running from the lateral femoral condyle to the anterior tibial spine, with two functional bundles (anteromedial and posterolateral). Most injuries are non-contact, occurring during sudden deceleration, sidestep cutting, pivoting on a planted foot, or landing from a jump with the knee in valgus, internal rotation, and near-extension. The mechanism produces a characteristic sequence: audible pop, immediate giving-way, large haemarthrosis within 4-12 hours, severe pain, and inability to bear weight.
The key symptoms of ACL Tear are: An audible pop or popping sensation in the knee at the moment of injury, reported by 50-70% of patients., Immediate sense of the knee 'giving way' or buckling, with inability to continue the activity., Rapid joint swelling within 4-12 hours from haemarthrosis (bleeding into the joint)., Severe pain at the moment of injury that often subsides somewhat within hours but worsens with weight bearing., Loss of full knee extension and reduced flexion from swelling and pain., Limp or inability to bear full weight in the acute phase., Persistent giving-way episodes (the knee buckling on pivoting or stair descent) in untreated complete tears..
Diagnosis combines mechanism of injury, clinical examination, and confirmatory imaging. The history of an audible pop, immediate giving-way, and rapid effusion in a young athlete is highly suggestive. Examination begins with inspection (swelling, bruising, deformity), palpation (joint line tenderness, effusion), assessment of range of motion, and ligamentous testing. The Lachman test (knee flexed 20-30°, anterior pull on the tibia) is the most sensitive bedside test (sensitivity 80-95%, specificity 90-95%); a soft endpoint and increased anterior tibial translation compared with the contralateral knee indicate ACL injury. The anterior drawer test (knee flexed 90°) is less sensitive in the acute setting. The pivot shift test (combined valgus, internal rotation, and flexion) is highly specific when positive but often difficult in conscious patients. KT-1000 arthrometer and Telos stress radiography quantify side-to-side anterior translation in research and pre-operative settings. McMurray and Apley tests assess meniscal injury. MRI is the gold standard imaging investigation, with sensitivity 86-100% and specificity 95-100% for complete tears; characteristic findings include disrupted ACL fibres, increased ACL signal, abnormal orientation, lateral femoral condyle and posterolateral tibial bone bruises, and associated meniscal or chondral injury. Plain radiographs are obtained to exclude fracture (Segond fracture — a small avulsion of the lateral tibia — is pathognomonic for ACL injury). Diagnostic arthroscopy is reserved for cases where examination and MRI are non-diagnostic, or as part of surgical reconstruction. Differential diagnosis includes PCL injury, posterolateral corner injury, meniscal tear without ACL injury, patellar dislocation, and tibial plateau fracture.
With appropriate management, 80-90% of athletes return to some form of sport at 9-12 months after reconstruction. Return to pre-injury level of pivoting sport is achieved by 65-80% in adults, and somewhat lower (~55-65%) in adolescent female athletes. Graft failure occurs in 3-15% overall, rising to 15-25% in young female pivoting athletes returning to sport before 9 months. Each additional month of rehabilitation before return reduces re-injury risk by 51% up to 9 months (Grindem et al. 2016). Long-term outcomes are dominated by post-traumatic osteoarthritis: 45-70% of patients develop radiographic OA at 10-20 years after ACL injury, irrespective of treatment, with higher rates after meniscectomy than meniscal repair or preservation. Symptomatic OA affects approximately 30% at 10-15 years. Quality of life is generally good but knee-related quality of life scores remain slightly below uninjured peers. Functional and psychological readiness (ACL-RSI) influence return to sport; fear of re-injury is the leading reason for not returning to pre-injury level. Long-term joint preservation depends on weight management, neuromuscular training, and meniscal preservation.
A sports medicine physician or orthopaedic surgeon assesses the injury, identifies associated injuries, advises on surgical versus non-surgical management, and oversees rehabilitation. Specialist physiotherapy is essential for return to sport; coordination between surgeon, physiotherapist, and athletic trainer determines outcomes.
Find specialists →Range of motion is regained over 4-6 weeks. Walking without crutches by 2-4 weeks. Stationary cycling and pool exercise by 6 weeks. Jogging at 12-16 weeks. Sport-specific drills at 4-6 months. Return to cutting and pivoting sport at 9-12 months with objective testing. Full graft remodelling continues for 12-24 months after surgery.
Follow a graded rehabilitation programme: gentle range of motion and isometric exercises in weeks 0-2; closed-chain strengthening at 2-6 weeks; running at 12-16 weeks; agility and cutting drills at 4-6 months; return to pivoting sport at 9-12 months after meeting objective criteria. Cycling and pool walking are useful adjuncts during early rehabilitation.
Choose a surgeon performing at least 50 ACL reconstructions per year with documented outcomes, access to all graft choices, experience with concomitant meniscal repair, and partnership with experienced sports physiotherapy. Look for centres offering objective return-to-sport testing.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
Ranked by patient outcomes and specialized experience.
Verifying top specialists in Tanzania.
Apply as specialist →Specialists who treat ACL Tear. Get expert guidance and personalized care.