Overview

An injury described as an LCL tear may involve the cord-like lateral collateral ligament alone, but significant trauma can also damage the broader posterolateral corner (PLC). This network helps control outward bowing and rotation of the knee.

That distinction matters: isolated low-grade LCL sprains and unstable combined PLC injuries do not follow the same treatment path.

Common Clues

Pain and tenderness along the outside of the knee or near the fibular head
A force to the inner knee, hyperextension or twisting trauma
Side-to-side or rotational instability
Difficulty trusting the knee during cutting or changing direction
Swelling and bruising after a substantial injury

Outer-knee pain can also come from the lateral meniscus, iliotibial band, proximal tibiofibular joint or nearby tendons.

The Nerve Check Matters

The common fibular nerve passes close to the fibular head. New numbness over the outer lower leg or top of the foot, difficulty lifting the foot or toes, or a foot that slaps while walking needs prompt assessment.

Diagnosis and Treatment

Assessment includes varus and rotational stability tests, nerve and circulation checks, and imaging when indicated. Clinicians look carefully for ACL, PCL, meniscus and other posterolateral damage.

Selected lower-grade isolated injuries may be managed with protection, bracing and progressive rehabilitation. Complete PLC injuries or marked combined instability often need specialist surgical assessment. Current expert consensus emphasizes individualized treatment and staged rehabilitation rather than one universal protocol.

When to Get Assessed

Prompt assessment is appropriate after major trauma, obvious instability, hyperextension, numbness or foot weakness. Seek urgent care for altered circulation, deformity, a cold or pale foot, or rapidly worsening neurological symptoms.

References

AAOS OrthoInfo. “Collateral Ligament Injuries.” https://orthoinfo.aaos.org/en/diseases--conditions/collateral-ligament-injuries/
LaPrade RF, et al. “A Contemporary International Expert Consensus Statement on the Evaluation, Diagnosis, Treatment, and Rehabilitation of Injuries to the Posterolateral Corner of the Knee.” https://pubmed.ncbi.nlm.nih.gov/40414466/

This information is for education only and is not a medical diagnosis. InjuryAtlas does not replace an assessment by a qualified health professional. If you have severe pain, visible deformity, numbness, loss of function, or symptoms that are getting worse, seek medical care promptly.

LCL and Posterolateral Corner Injury