see also: [[Knee soft tissue injury]] see: [The locked knee - BrJHM 2024 (bookends)](bookends://sonnysoftware.com/ref/DL/237819) - [online](https://storage.imrpress.com/IMR/hmed/application/10.12968/hmed.2022.0215.pdf) > [!key points] > - true locked knee needs to be differentiated from pseudo-locking, where pt has anatomically normal ROM but unable to fully extend either due to pain or muscle spasm > - acute locked knee should be managed urgently and discussed with orthopaedics > - MRI is best investigation to guide treatment → may require arthroscopy and debridement ## Differentials | Diagnosis | History | Clinical examination findings | | ------------- | ----------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Meniscus tear | - *twisting* mechanism<br>- acute onset of pain<br>- pain on moving knee | - episodes of painful or painless locking that occur intermittently (especially in bucket handle tears)<br>- ↓ ROM<br>- joint line tenderness<br>- may have +ve McMurray test<br>- *delayed* [[tibial plateau fracture#lipohaemarthrosis\|haemarthrosis]] | | ACL rupture | - *twisting* mechanism<br>- acute onset of pain<br>- pain on movement of knee | - can be difficult to examine acutely due to haemarthosis, pain, or inability to move knee<br>- ↓ ROM<br>- *Acute* haemarthrosis<br>- +ve lachman test or anterior drawer<br>- painfull or painless locking episodes | | Loose body | - may have history of trauma<br>- painful or painless | - episodes of painful or painless locking<br>- normal knee exam between acute episodes of locking | > [!caption] Table from Rhind et. al. 2024 "The Locked Knee" British Journal of Hospital Medicine ## Management flow chart ![[Pasted image 20261112110050.png]]