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First-time lateral patellar dislocation with osteochondral fracture — MSRA MCQ

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HardKnee InjuriesFirst-time lateral patellar dislocation with osteochondral fractureMSRA

A 19-year-old woman attends general practice the day after twisting on her planted right foot while playing netball. She felt her patella move laterally, then return into place as she fell. Her knee became markedly swollen within 2 hours. She can weight-bear with crutches. Examination shows a tense effusion, tenderness along the medial patellar border and a positive patellar apprehension test. She can perform a straight-leg raise and has no fixed deformity, neurovascular deficit or true locking. Plain knee radiographs obtained at an urgent treatment centre show the patella is located but demonstrate a 9 mm osteochondral fragment in the suprapatellar pouch. What is the most appropriate next step?

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

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Correct answer: C — Make an urgent referral to the orthopaedic knee service for assessment of the osteochondral fracture

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

This is a first-time lateral patellar dislocation that has spontaneously reduced: the transient lateral displacement, rapid effusion, medial patellar tenderness and apprehension are discriminating features. Preserved straight-leg raise makes extensor-mechanism rupture unlikely, while the absence of persistent deformity or neurovascular compromise means immediate reduction or emergency vascular management is not required. However, the radiographic osteochondral fragment changes management. UK NHS referral guidance advises radiography for every first-time patellar dislocation to identify an osteochondral fracture and recommends urgent knee-service referral when one is present. The fragment may represent clinically important articular injury or a loose body requiring specialist assessment; physiotherapy should not be the initial definitive pathway in this setting. B would be appropriate after a first-time patellar dislocation without osteochondral fracture. C is plausible because MRI can define associated soft-tissue and chondral injury, but specialist assessment should be expedited rather than delayed for primary-care MRI. D is reasonable initial symptomatic treatment for an uncomplicated injury, but does not address the urgent referral indication. E is inappropriate because intra-articular osteochondral injury requires assessment before return to pivoting sport.

Reference: Patello-Femoral Joint Dysfunction (Anterior Knee Pain) | NHS Tayside RefGuide (Undated; checked 15 August 2026) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/surgery-and-orthopaedics/orthopaedic-and-trauma-surgery/knee/patello-femoral-joint-dysfunction-anterior-knee-pain/?organization=nhs-tayside Dislocated kneecap | NHS (2026) — https://www.nhs.uk/conditions/dislocated-kneecap/