Locked knee

What is a locked knee?

Locked knee refers to a knee that can no longer fully extend. Essentially something happens to your knee and suddenly you cannot fully straighten it anymore. A “locked knee” is totally different than a knee that gradually deteriorates or is swollen and painful for a long time. In a “locked knee” situation, your knee was normal a moment ago. Then a specific event happens, usually a twisting or bending injury, or your knee suddenly gets stuck after kneeling or squatting, and you realize that you cannot straighten it anymore.

What injuries are associated with a locked knee?

The most common injury associated with a locked knee is a displaced locked bucket handle meniscal tear. This is essential a large meniscal tear that flips and jams the joint. In fact, a locked knee equals an unstable bucket handle until proven otherwise. Other rarer causes include an ACL tear that jams in extension (locking or pseudo-locking), a loose body or an unstable lateral meniscus with a flimsy posterior horn.

What imaging shoulder be obtained?

An MRI scan is the imaging modality of choice in the case of a locked knee. This should be obtained urgently, meaning you shouldn’t wait weeks or months. You shoulder have the MRI within a couple of days.

Can it wait?

It cannot wait. If a displaced bucket handle tear shoulder be caught early, the more likely your surgeon will be able to repair it. Therefore, it should be treated ideally within 6 weeks at the latest, if you want your surgery to have a good chance of success. If left untreated, odds are that your bucket handle will degenerate and will no longer be repairable. If that happens, you bucket handle may have to be removed instead, which means that you will lose a good chunk of your meniscus. This increases massively your chance to develop knee arthritis and trash your knee.  

How is a locked knee treated?

A locked knee shoulder be urgently treated surgically, ideally with arthroscopic meniscal repair, to reduce and fix the underlying bucket handle tear. If the aforementioned window of opportunity is lost, then arthroscopic meniscal debridement is performed, with the understanding that the prognosis is worse.