Collateral-ligament injury

Collateral injury ranges from a tender microscopic sprain to complete multiligament disruption. Ask about valgus, varus, rotation, hyperextension, deformity and whether the knee relocated. Establish immediate swelling, ability to continue, neurological symptoms and recurrent giving way. A contact valgus injury commonly affects MCL; true isolated LCL injury is less common and should prompt assessment of the posterolateral corner, cruciates and common peroneal nerve. High energy changes the question from sport rehabilitation to limb safety.

Inspect alignment, bruising, effusion and gait. Palpate the complete ligament rather than only the joint line: femoral and tibial MCL insertions and lateral femoral epicondyle, fibular head and posterolateral structures. Test straight-leg raise and joint lines. Document dorsiflexion, toe extension, eversion and dorsal-foot sensation, plus tibial nerve and pulses. In possible dislocation, measure ankle-brachial pressure and use urgent vascular pathways for any abnormality.

Stress examination at approximately 30 degrees helps isolate the collateral ligament; opening in full extension implies more extensive capsular or cruciate injury. Compare side-to-side and describe endpoint rather than writing stable or unstable alone. Dial and rotational tests assess posterolateral injury. Do not force a painful knee with possible fracture. Acute guarding can hide laxity, so repeat after swelling control, under specialist review or under anaesthesia when operative treatment is planned.

Obtain AP and lateral radiographs after meaningful trauma and add views for avulsion or alignment. Pellegrini-Stieda calcification is a later sign of previous MCL injury, not an acute management target. MRI defines tear site, displacement and combined ACL, PCL, corner, meniscal and cartilage injury. Stress radiographs and long-leg alignment studies are specialist tools for chronic instability. Imaging cannot replace serial neurovascular examination in a suspected reduced dislocation.

Isolated MCL injuries have strong healing potential. Use short protection and a hinged brace for symptomatic or higher-grade laxity, allow weight bearing as tolerated when fracture and multiligament injury are excluded, and begin early extension, flexion and quadriceps activation. Progress hip strength, balance, running and cutting. Review grade III injury to ensure valgus opening is resolving and no distal entrapment, avulsion, ACL instability or malalignment undermines healing.

LCL and posterolateral injury has a lower threshold for early referral. Complete injuries can heal elongated and cause persistent varus and rotational instability. Acute repair may suit selected avulsions and tissue patterns; reconstruction is used for midsubstance or chronic deficiency. Correct relevant varus alignment and address ACL or PCL injury together, because an untreated corner can overload a cruciate graft. Peroneal palsy requires serial motor documentation and nerve expertise.

Surgery is considered for open injury, displaced bony avulsion, ligament entrapment, multiligament knee dislocation, persistent gross instability, failed non-operative healing or combined reconstruction need. Timing balances tissue repairability against swelling and motion. Consent includes stiffness, infection, thrombosis, residual laxity, graft failure, nerve injury and later osteoarthritis. Vascular repair and fracture stability take priority in limb-threatening combined trauma.

Follow range, endpoint, effusion, quadriceps control, gait and real-world stability. Avoid return while valgus or varus pain and laxity persist. A stable knee with restored strength can return progressively through running, direction change and contact. Recurrent instability warrants alignment and combined-ligament reassessment rather than repeated bracing. Teach urgent return for coolness, new foot weakness, escalating calf pain or disproportionate swelling.