ACL, PCL, MCL and LCL injuries: a patient guide

A ligament may be overstretched, partly torn or completely disrupted. The name of the injured ligament describes its location and stabilising role, but a clinical assessment is needed to judge functional severity and check nearby structures.

The ACL limits forward shift and rotation of the shin; the PCL limits backward shift. The MCL supports the inner knee against inward collapse, while the LCL contributes to stability along the outer knee. A combined injury can create looseness in several directions.

Twisting, direct impact, awkward landing or a high-force knee displacement can damage these structures. People with a ligament injury may notice pain, swelling, bruising, restricted motion or buckling. Where the knee hurts does not always identify the only injured tissue, especially after substantial trauma.

Leave the activity and keep the knee from twisting. Support it in a comfortable position, elevate it when swollen and use a wrapped cold pack if helpful. Do not repeatedly pull or push the joint to find out how loose it is.

A clinician checks movement, ligament stability, circulation, nerve function and possible damage to bone, cartilage or tendons. Knee bracing may protect a selected range or direction. Physiotherapy then builds motion, strength, balance and task-specific control. For sport, progression includes increasingly demanding movement and is completed only after suitable return-to-sport testing.

Emergency assessment is needed if the knee is deformed, the foot is colder or paler than the other side, a pulse seems absent, or new numbness or weakness develops. These signs can accompany blood-vessel or nerve injury. Prompt medical review is also sensible if the knee locks, will not bear weight, rapidly swells or repeatedly collapses.

Ask which ligament or combination is damaged, whether circulation and nerves are normal, what weight-bearing and motion limits apply, how any brace should be worn, and which strength and control targets will show that progression is safe.