Inferior patella dislocation in an elderly patient after a fall: A case report

Inferior intra-articular patella dislocation is rare and comprises horizontal (type 1) and the more common vertical (type 2) dislocations in young and elderly patients respectively. In this case report, we describe a case of an elderly patient who presented with a type 2 dislocation after a fall. The mechanisms of inferior patella dislocation, their classification, key imaging features and treatment options are discussed.

A 75-year-old woman presented with a right knee fixed flexion deformity after a fall. Preoperative imaging confirmed a vertical intra-articular patella dislocation with a femoral trochlear osteochondral defect and lax though grossly intact patella tendon. Closed reduction was performed under general anaesthesia. Knee arthroscopy confirmed the presence of a femoral trochlear osteochondral defect whose edges were subsequently smoothed and there was debridement of scant debris with thorough irrigation of the joint. Postoperative imaging demonstrated anatomical alignment, however, there was a new nondisplaced medial femoral trochlear. The patient however was able to mobilise well in a range of motion brace set at 0-30 degrees and was discharged 1-day post operatively.

Inferior patella dislocation is rare and this article highlights its types and imaging features which determine the most appropriate management.