Diagnostic Performance of the Lachman Test for ACL Tears

Test Performance and Timing

• The Lachman test performs optimally when delayed 4-5 days post-injury, achieving 84% sensitivity and 96% specificity for anterior talofibular ligament assessment 1
• Consider delayed examination (4-5 days post-injury) to optimize test performance when initial acute examination is equivocal 1

Diagnostic Accuracy and Comparison with Other Tests

• The American College of Radiology recommends obtaining MRI for definitive diagnosis when clinical tests are discordant or surgical planning is needed 2
• MRI sensitivity is 93-98.57% and specificity is 87.5-100% 2
• Ultrasound can detect ACL injuries with 90% sensitivity and 97% specificity as an alternative to immediate MRI 4

Clinical Application and Important Caveats

• The British Journal of Sports Medicine suggests that test performance is significantly affected by timing of examination (acute vs. post-acute) 1
• The Journal of the American College of Radiology notes that the presence of joint effusion or hemarthrosis limiting examination can affect test performance 2