The screw home mechanism is a movement of the joint that is key to keeping the knee stable while standing upright.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

 

How the screw home works

It is a rotation between the tibia and femur occurring at the end of knee extension, between full extension (0 degrees) and 20 degrees of knee flexion.

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Peer-reviewed papers

  • Quote:

    "As the medial femoral condyle is longer than the lateral condyle, the tibia rotates internally on the femur during the first stage of flexion....[this is called] the screw‐home movement....During knee flexion, the patella moves into the femoral trochlear groove while rotational movement adjusts the patellofemoral joint stability; this is known as the capture mechanism of the femur....[and it] prevents abnormal patellar tracking in the early stage of knee flexion...the screw‐home mechanism is the insurance of the capture mechanism, and plays an important role in guiding patellar sliding into the....groove."

    Citation: Zhang LK, Wang XM, Niu YZ, Liu HX, Wang F. Relationship between Patellar Tracking and the "Screw-home" Mechanism of Tibiofemoral Joint. Orthop Surg. 2016 Nov;8(4):490-495. doi: 10.1111/os.12295. PMID: 28032709; PMCID: PMC6584384.

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Dr Sheila Strover (Editor)
BSc (Hons), MB BCh, MBA

See biography...