Overview
what it is and why it mattersThe lateral collateral ligament (LCL) is the cord-like ligament along the outside of your knee that keeps it from buckling outward. It's much less commonly injured by itself than the MCL on the inside; more often, the LCL gets torn as part of a larger injury to the entire posterolateral corner of the knee (which includes a couple of other small stabilizing ligaments). Most LCL injuries come from a high-energy hit to the inside of the knee or a hyperextension twist.
Symptoms
what you may noticePain and tenderness on the outer side of your knee — especially right over the bony bump at the top of the fibula where the LCL attaches — are the hallmark findings. Swelling along the outside of the knee typically develops within hours of the injury. With a more severe sprain (grade 2 or 3), you may feel your knee buckle or give way outward when you try to stand or walk.
When the posterolateral corner is also involved, the instability is more pronounced: your knee may twist or rotate in ways it shouldn't, particularly when changing direction or going downstairs. Stiffness and limited range of motion are common in the first few days. Bruising may appear on the outer knee and can track downward along the lower leg.
Diagnosis
exam first, imaging secondPain and tenderness on the outside of the knee, especially at the bony bump where the LCL attaches. Two specific exam moves (the varus stress test and the dial test) check whether the LCL and the rest of the posterolateral corner are intact. MRI shows all three layers of the outer side of the knee. Your surgeon will also carefully check the function of the peroneal nerve, which runs right behind the area and can be stretched in posterolateral corner injuries.
Treatment Path
how care progresses at OSI1
Bracing & protected weight-bearing
Grade 1 and 2 isolated LCL sprains often heal in a hinged knee brace, followed by progressive return to activity through rehab.
2
Physical therapy
Strengthening the muscles that stabilize the outside of the knee, plus balance and proprioception drills to retrain how the leg responds under load.
Surgical Options at OSI
if non-operative care isn't enoughComplete (grade 3) LCL tears and all posterolateral corner injuries are considered for surgical repair or reconstruction — these structures have poor healing potential on their own, and untreated, they cause significant rotational instability that grinds down the joint.
Providers Who Treat LCL Sprain
sports-medicine team
Further Reading
authoritative sourcesExternal patient-education references and related OSI pages for additional background: