key: cord-0006562-zt5l60ih
authors: Arevalo-Lorido, J. C.; Bureo-Dacal, J. C.; Romero-Requena, J.; Ramos-Salado, J. L.; Bureo-Dacal, P.
title: Tuberculosis complicated by ARDS
date: 2001
journal: Ir J Med Sci
DOI: 10.1007/bf03173895
sha: 1fdf5229954edb6b68ac59c512ca791473439fea
doc_id: 6562
cord_uid: zt5l60ih

nan

Dear Editor, Inferior dislocation of the patella is unusual without trauma and without rupture of the quadriceps or patellar tendons.

A 75-year-old female presented with an acutely locked knee, having developed sudden onset of pain in her right knee while boarding a bus. On examination, the right knee was locked in 40' flexion and attempted movement caused pain. The patella was low lying and there was no evidence of an extensor mechanism rupture. Plain radiographs (see Figure 1 ) and magnetic resonance imaging (M1RI) scan confirmed an inferior dislocation of the patella with intact quadriceps and patellar tendons. Under general anaesthetic, downward pressure was applied to the superior pole of the right patella while extending the knee. This manoeuvre reduced the patellar dislocation and resulted in full range of movement of the knee. The patient made an uneventful recovery.

Patellar dislocation usually occurs due to a twisting injury or a direct blow to the knee. Lateral dislocation is the most common type, but there are reports of intra-articular, superior' and inferior' patellar dislocations. Joshi' described the rare inferior dislocation of the patella in which a patient sustained a twisting injury to the knee and the patella displaced out of the groove. The mechanism of dislocation is believed to be that of a supenor pole osteophyte engaging in the intercondylar notch. In our case, this occurred without trauma and resulted in the knee being locked in 40° flexion. Our method of reduction also differed from Joshi's in that downward pressure on the patella was needed to reduce the superior pole osteophyte. 

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Inferior dislocation of the patella: an unusual cause of a locked knee