Performing the Test: The patient's leg should be relaxed for this test. The examiner should passively bend the affected leg to about 30 degrees of flexion. While palpating the medial joint line, the examiner should apply a valgus force to the patient's knee. A positive test occurs when pain or excessive gapping occurs (some gapping is normal at 30 degrees). Be sure to not include rotation of the hip in your application of force. Next the examiner should repeat the test with the knee in neutral (0 degrees of flexion). A positive test occurs when pain or gapping is produced. There should be no gapping at 0 degrees.
Diagnostic Accuracy:At 30 degrees: Sensitivity: .86-.96 ("Tears of the medial collateral ligament: magnetic resonance imaging findings and associated injuries," "Evaluation of knee instability in acute ligamentous injuries").
Importance of Test: The medial collateral ligament is important for resisting valgus force at the knee due to its attachments along the femur, meniscus, and tibia. The MCL also plays a major role in restraining tibial external rotation. Surgical severing of the superficial portion of the MCL was shown to increase tibial external rotation at 90 degrees by about 3 times (Ellenbecker, 2000). According to Neumann, the MCL attaches to the medial epicondyle proximally and posterior to the distal attachment of the pes anserinus distally on the antero-medial tibia. The deeper fibers of the MCL are shorter than the superficial fibers and also attach to the posteromedial capsule, meniscus, and semimembranosus tendon. Because the deeper fibers are shorter than the superficial fibers, they are more likely to be injured when stressed with a valgus force, even though the superficial fibers provide the primary resistance to valgus force! The superficial fibers, on the other hand, are more likely to be stressed with external rotation of the tibia on the femur (or internal rotation of femur on tibia). With the attachment of the MCL to the meniscus, whenever the mechanism of injury affects the MCL, be sure to check the meniscus for injury as well. At 0 degrees, there is usually no gapping that occurs when a valgus stressed is applied, so if gapping occurs during the test, severe injury is suspected i.e. ACL, PCL, MCL, capsule (no gapping because the MCL, posteromedial capsule, hamstrings, oblique popliteal ligament, and parts of the ACL are most taut in full extension). In the position of 30 degrees, some gapping occurs, because the MCL and other structures are no longer stressed maximally, but the MCL is the primary stabilizer in this position. The MCL overall is one of the most important ligaments for stability of the knee. With a hypermobile knee, due to a sprained MCL, it is important to take extra precautions to decrease risk of further injury. With a lax MCL, the ACL becomes increasingly stressed with valgus forces, especially at 45 degrees of flexion (Ellenbecker, 2000). Remember the MCL is the primary valgus restraint in the flexed knee; without it, the ACL is prone to injury.
Note: these tests should only be used by properly trained health care practitioners