AFT Calculator
Calculate anterior femoral translation (AFT) grade from Lachman test measurements for ACL knee injury assessment. Free online orthopedic evaluation tool with grading, charts, and interpretation.
About This Calculator
The Anterior Femoral Translation (AFT) Calculator helps orthopedic clinicians, sports medicine professionals, and patients evaluate ACL (anterior cruciate ligament) injury severity based on Lachman test findings. By entering the measured tibial translation, side-to-side difference, and endpoint quality, you receive an immediate Lachman grade (0-3) with clinical interpretation.
The ACL is one of the major ligaments stabilizing the knee, preventing excessive forward movement of the tibia relative to the femur. The Lachman test, performed at 30 degrees of knee flexion, is the most sensitive and specific physical examination maneuver for diagnosing ACL tears. Translation is graded on a scale from 0 (normal, <3 mm) to 3 (severe, >10 mm), with endpoint quality providing additional diagnostic information.
Grading system: Grade 0 (<3 mm, firm endpoint) indicates an intact ACL. Grade 1 (3-5 mm, firm endpoint) suggests a partial ACL tear with some intact fibers. Grade 2 (5-10 mm, soft endpoint) is consistent with a complete ACL tear. Grade 3 (>10 mm, absent endpoint) indicates a complete ACL tear with possible injury to secondary stabilizers including the collateral ligaments and capsule.
Regional Notes: ACL injury management varies globally. In India, ACL reconstruction is commonly performed using hamstring tendon autografts, with costs ranging from ₹80,000 to ₹2,50,000. In the United States, ACL reconstruction is one of the most common orthopedic procedures, with over 200,000 performed annually, typically using bone-patellar tendon-bone or hamstring autografts. In the United Kingdom, the NHS performs approximately 15,000 ACL reconstructions per year, with waiting times averaging 12-18 weeks for non-emergency cases. Rehabilitation protocols and return-to-sport timelines are consistent across regions, typically 9-12 months post-operatively.
Frequently Asked Questions
What is anterior femoral translation?
Anterior femoral translation (AFT) measures how far the tibia moves forward relative to the femur during the Lachman test. Normal AFT is under 3 mm. Measurements above 3 mm may indicate ACL injury, with Grade 1 (3-5 mm), Grade 2 (5-10 mm), and Grade 3 (>10 mm) corresponding to increasing ligament damage severity.
What is the Lachman test?
The Lachman test is the gold standard clinical test for ACL integrity. Performed with the patient supine and knee flexed at 30 degrees, the examiner stabilizes the femur while pulling the tibia forward. A firm endpoint suggests an intact ACL, while a soft or absent endpoint indicates partial or complete ACL tear. Sensitivity is 85% and specificity is 94% for ACL tears.
How is AFT graded for ACL injuries?
AFT is graded on a 0-3 scale based on translation amount and endpoint quality. Grade 0: <3 mm translation with firm endpoint (normal). Grade 1: 3-5 mm with firm endpoint (partial ACL tear). Grade 2: 5-10 mm with soft endpoint (complete ACL tear). Grade 3: >10 mm with absent endpoint (complete tear with secondary stabilizer injury).
What is a normal side-to-side difference in AFT?
A side-to-side difference of less than 3 mm between the injured and uninjured knee is considered normal. A difference of 3-5 mm is suggestive of a partial ACL tear, while more than 5 mm difference strongly indicates a complete ACL tear. Bilateral comparison is essential for accurate diagnosis.
Can an ACL tear heal without surgery?
The ACL has poor healing capacity due to its intra-articular location and limited blood supply. Grade 1 sprains (partial tears) may heal with conservative management including bracing and physical therapy. Complete ACL tears (Grade 2-3) typically require surgical reconstruction for athletes or individuals with high activity demands. Non-operative management with activity modification and rehabilitation is an option for some patients.
What other tests complement the Lachman test for ACL assessment?
The anterior drawer test (performed at 90 degrees knee flexion) and the pivot shift test (assesses rotatory instability) complement the Lachman test. MRI is the gold standard imaging modality for confirming ACL tears, with 87% sensitivity and 93% specificity for complete tears.
How long does ACL recovery take after surgery?
ACL reconstruction recovery typically follows a 6-12 month timeline. Phase 1 (weeks 1-4): protection and swelling management. Phase 2 (weeks 4-12): range of motion restoration and strengthening. Phase 3 (months 3-6): advanced strengthening and neuromuscular training. Phase 4 (months 6-12): sport-specific training and return to play clearance.
What factors affect Lachman test accuracy?
Lachman test accuracy depends on examiner experience, patient relaxation, and proper positioning. False negatives can occur with hemarthrosis (blood in the joint within the first 2 hours), muscle guarding, or a bucket-handle meniscus tear that blocks translation. False positives may result from generalized ligamentous laxity or multi-ligament knee injuries.