Locked knee

Written by Dr Sheila Strover on March 14, 2025

A knee is considered to be locked when following some incident the patient finds themself unable to take the knee through a full range of movement. Page updated March 2024 by Dr Sheila Strover (Clinical Editor)

What causes a locked knee?

When we talk of a 'locked knee' it is implied that the knee was fine, but something has suddenly gone wrong and it can no longer fully flex and extend.

This is usually due to something becoming stuck in the joint between the femur and tibia, such as a bit of torn knee meniscus or a loose fragment of joint cartilage.

"...Locked knee is an orthopaedic condition requiring urgent treatment....the cause of the mechanical obstruction may only be apparent during arthroscopic examination of the knee joint...."

MF Mohd Miswan et al

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Is locking serious?

A locked knee may unlock without help, but it implies that there is an underlying problem like a meniscus tear, and the locking may re-occur.

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Is knee locking permanent?

A locked knee should be managed as soon as possible by an experienced practitioner, who may be able to manipulate the knee to relieve the obstruction, and the patient should regain full range of motion.

If manipulation fails arthroscopic surgery may be needed.

The longer the period before unlocking, the greater the damage may become, and eventually may result in loss of meniscus tissue or damage to the joint cartilage.

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