MCL Sprain Diagnosis

Medial knee ligament sprains are graded 1, 2 or 3 depending on the severity of the injury. Here we explain how a medial collateral knee ligament sprain is diagnosed. Grade one injuries are regarded as a mild sprain, grade two as moderate and grade three as severe, often involving a complete tear of the ligament.

Grade 1 symptoms

  • For a grade 1 MCL injury, there may be mild tenderness on the inside of the knee but usually no swelling.
  • The patient is likely to be able to walk or even run with minimal symptoms but not at 100% and they will likely experience some form of discomfort.
  • When the knee is assessed using stress tests such as the valgus stress test, the ligament will feel stable with a hard end feel (no laxity) and minimal movement but there will be some degree of the pain somewhere along the ligament.

Grade 2 symptoms

  • Grade 2 injuries are usually associated with significant tenderness and pain on the inside of your knee.
  • You will likely have some swelling.
  • The valgus stress test will usually reproduce symptoms and you may have some degree of laxity (excess movement) in your knee. However, there will be a definite endpoint as the ligament is not completely ruptured.

Grade 3 symptoms

  • Grade 3 injuries involve a complete (or near-complete) tear of the ligament.
  • Pain levels can sometimes vary and it may feel less painful than a grade 2 MCL sprain. The reason for this is that the nerves supplying pain signals have also ruptured.
  • You will have significant swelling and may feel that you have a very wobbly or unstable knee.
  • Assessment tests, such as the valgus stress test will show significant movement in the joint (laxity.) The test will probably not have a definite endpoint when the medial ligament is stressed as there is no ligament stopping the movement.
  • A grade 3 MCL injury often occurs with other injuries in the knee at the same time, such as an ACL sprain.

Valgus stress test


The valgus stress test is a diagnostic test that is used in cases of suspected MCL injuries. The therapist takes hold of the leg, ensuring the knee is slightly bent (approx 30 degrees). They stabilize the thigh whilst applying outward pressure on the lower leg (tibia) and this stretches the medial ligament.

Pain on the inside of the knee and or excessive movement (laxity) with an altered end feel in the ligament indicates a positive test. The degree of damage can then be determined by how much movement/stability there is.

This article has been written with reference to the bibliography.