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Suspected displaced traumatic meniscal tear causing a true locked knee — MSRA MCQ

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HardKnee InjuriesSuspected displaced traumatic meniscal tear causing a true locked kneeMSRA

A 27-year-old man attends a GP-led urgent treatment centre 36 hours after twisting his right knee while pivoting during football. He felt medial joint-line pain immediately and developed a moderate effusion later that evening. Since the injury, the knee has remained persistently blocked: he cannot actively or passively extend beyond 20 degrees of flexion and cannot flex beyond 80 degrees. He reports no intermittent release of the block. There is medial joint-line tenderness. The knee is not hot or erythematous. Lachman, posterior drawer and collateral ligament testing are limited by pain but show no gross laxity. He can perform a straight-leg raise. Distal pulses, sensation and ankle movements are normal. Plain knee radiographs show no fracture or loose body. What is the most appropriate management today?

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

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Correct answer: C — Arrange urgent orthopaedic assessment today for a suspected displaced meniscal tear; provide analgesia and crutches without awaiting MRI.

Explanation lettering: C = shown as A · A = shown as C

This is a true locked knee after a twisting injury: there is a persistent mechanical block, with loss of more than 15 degrees of extension and inability to flex to 90 degrees. Together with joint-line tenderness and a delayed effusion, this is concerning for a displaced meniscal tear, particularly a bucket-handle tear. A normal radiograph excludes neither meniscal displacement nor other internal derangement. Urgent orthopaedic assessment is required because a locked knee may need prompt arthroscopic management. MRI should not delay referral in this situation; local NHS guidance specifically states that MRI is unnecessary where a locked knee requires urgent orthopaedic assessment with a view to arthroscopy. B is attractive because MRI usually defines suspected meniscal pathology, but it is the wrong sequence for a true locked knee. C, D and E would be appropriate for a stable knee with pain, catching, giving-way or reduced movement that is not mechanically locked, particularly after an initial period of rehabilitation. They are inappropriate where fixed loss of extension and flexion suggests displaced intra-articular tissue.

Reference: NHS Tayside RefGuide: MRI Criteria (Next review date 02/07/2027) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/surgery-and-orthopaedics/orthopaedic-and-trauma-surgery/knee/mri-criteria/ NHS Tayside RefGuide: Meniscal Problems (Next review date 02/07/2027) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/surgery-and-orthopaedics/orthopaedic-and-trauma-surgery/knee/meniscal-problems/?organization=nhs-tayside&useNavigation=true