Diagnosis of medial collateral ligament (MCL) sprain

A patient with a medial collateral ligament (MCL) sprain presents with knee pain and local tenderness and, in complete tears, a feeling of instability. Clinical examination reveals tenderness over the MCL and, in more severe injuries, local swelling.

The MCL is tested by replicating the most frequent mechanism of injury. Application of a valgus stress with the knee flexed to 20 to 30 degrees will induce pain. Marked laxity of the MCL may be apparent in a complete tear; in these cases, examination must include an assessment for associated injuries to the anterior cruciate ligament or menisci (medial and lateral), which can be found in up to 75% of cases.

No investigations are required for grades 1 and 2 MCL sprains; see Overview of MCL sprain. A magnetic resonance imaging (MRI) scan may be indicated in cases of grade 3 (complete) tears to look for associated injuries.