Helfet’s Test

Helfet’s Test is a functional orthopedic assessment used to evaluate the screw-home mechanism of the knee—the natural external rotation of the tibia (shin bone) relative to the femur during the last 20-30° of knee extension. It helps screen for mechanical derangement involving the knee meniscus or cruciate ligaments, or limitations due to pain or swelling.

How the Test is Performed

• Client position: Sitting with knees flexed to 90°, legs hanging off the edge of the table, relaxed.

• The examiner can mark the center of the patella and tibial tuberosity for observation.

• The client is asked to actively extend the knee fully from the hanging position.

• The examiner observes the motion of the tibial tuberosity relative to the patella as the knee extends.

  • Normally, the tibial tuberosity shifts slightly laterally (“screw-home” mechanism) as the tibia externally rotates in the last stage of extension.

• A positive test: The absence of this normal lateral movement or “lock out” (failure of external tibial rotation) may indicate a meniscal injury, cruciate ligament pathology, or muscular imbalance blocking normal knee extension.

• The test is invalid if the knee has significant effusion (joint swelling), limiting movement.

Clinical Significance

• Absence of the screw-home mechanism can be a sign of meniscus tear, cruciate ligament injury, joint adhesions, or significant neuromuscular imbalance.

• Sudden “locking” or pain with attempted extension may further point to a meniscal obstruction or loose body within the joint.

• The test helps distinguish between purely muscular versus intra-articular mechanical restrictions at the knee.

Assessment

• Use Helfet’s Test for clients with knee pain, limitation in extension, locking, clicking, or prior surgery/injury.

• Document presence or absence of lateral tibial rotation, “locking,” pain, or abnormal tracking.

• Combine with other knee special tests (McMurray’s, Apley’s, Drawer, Thessaly) for comprehensive assessment.

Treatment

• If positive:

  • Avoid deep tissue work, aggressive stretching, or mobilization when mechanical derangement is suspected.

  • Support with gentle soft tissue release, active movement within pain-free ranges, and patient education about avoiding forced extension or deep flexion until full assessment.

  • Refer for orthopedic/physio evaluation and imaging if mechanical block, locking, or suspected intra-articular pathology is present.

• Address compensatory muscle tightness or imbalance only if cleared for manual work, focusing on function and pain relief.

Safety and Referral

• Refer promptly if inability to extend, locking, or a “hard stop” is encountered—indicating probable meniscal or ligamentous injury.

• Collaborate with an interdisciplinary team for evaluation and treatment, especially post-injury or post-op clients.