Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Suspected knee dislocation is a limb-threatening vascular injury
High-energy or spontaneously reduced multiligament injury can disrupt the popliteal artery despite a knee that appears aligned and palpable pulses; delay in recognising ischaemia can lead to amputation.
Action: Assess and document pulses, capillary refill, ankle-brachial pressure and common peroneal and tibial nerve function immediately, reduce any deformity, immobilise, obtain urgent vascular imaging and specialist input for abnormal or equivocal perfusion, and admit for serial neurovascular observation when multiligament injury is suspected.
Synopsis
Differentiate ACL and PCL mechanisms and examination patterns, recognise multiligament and vascular emergencies, use MRI after appropriate radiographs, begin criterion-led rehabilitation, and select reconstruction from instability and goals rather than imaging alone.
ACL injury typically follows pivot, deceleration or landing with a pop, rapid haemarthrosis and later giving way; PCL injury follows posterior tibial force or flexed-knee fall and may be subtler.
A spontaneously reduced knee dislocation can look normal. Document perfusion, ankle-brachial pressure and peroneal and tibial nerve function and use serial or vascular imaging pathways when multiligament injury is possible.
Obtain trauma radiographs first to identify fracture or avulsion. MRI maps ACL, PCL, menisci, cartilage and corners after immediate limb threats are addressed.
Key red flags
Knee deformity, gross multidirectional instability, reduced pulse, cool foot or ankle-brachial pressure below the local normal threshold requires immediate vascular and orthopaedic escalation.
Investigation priorities
01
Immediate neurovascular assessmentFirst step
Detect popliteal artery and peroneal or tibial nerve injury.
02
First-line trauma radiographsFirst line
Identify fracture, tibial-spine or PCL avulsion and alignment.
Management branches
ThreatTreat as knee dislocation
Deformity, multiligament laxity or abnormal perfusion suggests dislocation or vascular injury.
Reduce deformity, immobilise and document pulses, ankle-brachial pressure and nerve function before and after intervention.
Use urgent CT angiography and vascular consultation for abnormal or changing perfusion.
RehabilitationCreate a quiet stable functional knee
Isolated injury is confirmed without a limb threat or urgent repairable block.
Key medicines
Short-term anti-inflammatory analgesiaUse a licensed topical NSAID or one oral NSAID at the lowest effective adult dose for the shortest period that supports motion and rehabilitation, adding gastroprotection when oral treatment and risk assessment indicate it.
Post-reconstruction thromboprophylaxis when indicatedUse the exact mechanical and pharmacological regimen from the current local knee-ligament surgery pathway only after individual venous-thrombosis, bleeding, weight-bearing, travel, contraception and previous-event assessment.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.