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Combined posterior cruciate ligament and posterolateral-corner injury — MSRA MCQ

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HardKnee InjuriesCombined posterior cruciate ligament and posterolateral-corner injuryMSRA

A 29-year-old amateur rugby player attends a GP-led urgent treatment centre 5 days after a tackle forced his planted right knee into hyperextension and varus. He had immediate swelling and was unable to continue playing. He now walks with crutches because the knee feels unstable when changing direction. There is a moderate effusion and posterolateral joint-line tenderness. Posterior drawer testing demonstrates marked posterior tibial translation with a soft endpoint. Varus stress testing produces lateral gapping at 30 degrees of flexion. The dial test shows increased external rotation of the right tibia compared with the left at both 30 and 90 degrees of knee flexion. He can perform a straight-leg raise and has no fixed loss of extension. Dorsiflexion and eversion are normal; distal sensation, capillary refill and pedal pulses are normal. Knee radiographs show no fracture. What is the most appropriate management today?

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Correct answer: D — Refer urgently for orthopaedic assessment for suspected combined PCL and posterolateral-corner injury

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

This mechanism (hyperextension with varus force), marked posterior drawer and increased tibial external rotation on dial testing indicate a posterior cruciate ligament (PCL) injury with posterolateral-corner (PLC) involvement. Varus gapping supports injury to the lateral stabilising structures. This is not an isolated PCL injury suitable for an initial rehabilitation-led approach: combined PCL/PLC injuries are complex, potentially disabling and require prompt specialist assessment. UK NHS guidance advises immediate orthopaedic opinion where PLC injury accompanies PCL injury, because repair may be time-sensitive, with an identified window of less than 3 weeks. Normal pulses, sensation and ankle movements are reassuring and mean there is no current evidence of vascular compromise or common peroneal nerve palsy; however, their absence does not make combined PCL/PLC injury appropriate for routine MRI, MSK triage or delayed reassessment. A is inappropriate because imaging arranged through primary care may delay specialist decision-making. B would be reasonable initially for many isolated ligament injuries, including some isolated PCL tears, but not this combined pattern. C introduces an avoidable intermediate pathway. E underestimates the established structural injury; neurological deterioration would require emergency action, but urgent orthopaedic referral is already indicated.

Reference: NHS Greater Glasgow and Clyde MSK Index: Ligament injuries (2024 (site metadata; checked 16 August 2026)) — https://www.rightdecisions.scot.nhs.uk/ggc-msk-index/knee/ligament-injuries/ NHS Tayside RefGuide: Knee (Checked 16 August 2026) — https://www.rightdecisions.scot.nhs.uk/nhs-tayside-refguide/surgery-and-orthopaedics/orthopaedic-and-trauma-surgery/knee/?UNLID=678850159202611919452