How is the Lachman test performed and interpreted?

• A. With the knee flexed about 20-30 degrees, stabilize the femur and apply gentle anterior translation to the tibia; increased laxity compared with the contralateral knee indicates ACL injury.
• B. With the knee extended, apply anterior translation to the tibia; normal laxity indicates ACL injury.
• C. With the knee flexed to 90 degrees, apply posterior translation to the tibia; increased laxity indicates ACL injury.
• D. With the knee extended, rotate tibia externally while applying valgus stress; no laxity indicates ACL injury.

Answer: (D)