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Acute osteochondral fracture following lateral patellar dislocation — MSRA MCQ

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ModerateKnee InjuriesAcute osteochondral fracture following lateral patellar dislocationMSRA

A 19-year-old woman attends a GP-led urgent treatment centre 2 hours after pivoting on her left leg during netball. She felt the patella displace laterally and it reduced spontaneously when she extended the knee. She has a moderate effusion and medial patellar-border tenderness. She can perform a straight-leg raise and has full passive extension. There is no tibiofemoral instability, joint-line tenderness, neurovascular deficit or fixed deformity. Anteroposterior, lateral and skyline radiographs show a located patella and a 7 mm osteochondral fragment in the lateral suprapatellar recess. What is the most appropriate management today?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Make an urgent referral to the orthopaedic knee service for an acute osteochondral fracture

Explanation lettering: E = shown as A · D = shown as B · B = shown as C · A = shown as D · C = shown as E

This is a first-time lateral patellar dislocation that has spontaneously reduced, but radiography demonstrates an osteochondral fragment. This is the discriminating feature: acute osteochondral fractures after patellar dislocation require urgent referral to the knee service. A loose fragment may require assessment for fixation or arthroscopic removal, rather than routine rehabilitation alone. A is appropriate for an uncomplicated first-time patellar dislocation when radiographs exclude an osteochondral fracture. B is attractive because MRI can define the cartilage injury and donor site, but imaging should be organised through the urgent specialist pathway; obtaining MRI first may delay definitive assessment. D inappropriately treats this as an uncomplicated instability episode and delays review despite the intra-articular fragment. E is relevant to recurrent dislocation without an acute osteochondral injury, but recurrence is not required before referral in this case.

Reference: Patellar Instability | NHS Tayside RefGuide (Not stated; next review date 02 July 2027) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/surgery-and-orthopaedics/orthopaedic-and-trauma-surgery/knee/patellar-instability/?UNLID=19258254320263664137