Purpose: To assess the integrity of the MCL and ACL (rotary instability).
Test Position: Supine.
Performing the Test: The examiner should lift the tested leg off the table with the knee fully extended. Place the heel of one hand behind the fibular head of the patient. Use the other hand to grasp the tibia, while palpating the medial joint line. While maintaining a valgus force and internal rotation of the tibia throughout the test, slowly flex the patient's knee (note: the test starts by putting the tibia in the abnormal position!). A positive test occurs when the lateral tibial plateau begins anteriorly subluxed and returns to neutral as you flex the knee to around 30 degrees ("Users' Guide to the Musculoskeletal Examination: Fundamentals for the Evidence-Based Clinician").
Diagnostic Accuracy: ACUTE: Sensitivity: .32; Specificity: 1.0; +LR: 1.3; -LR: 1.0; CHRONIC: Sensitivity: .40; Specificity: .97; +LR: 7.7; -LR: .8 ("Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis").
Importance of Test: This test is used mainly to assess anterolateral stability to the knee by recreating the knee buckling feeling. It requires an intact MCL (which is why it also tests the MCL) in order to transfer the valgus forces into a compression force on the lateral compartment. As the knee is flexed to about 30 degrees, the Iliotibial Band changes from an extensor moment arm to a flexor moment arm and shifts the subluxed tibia back into normal position. It should be noted that individuals who have been ACL deficient for awhile may have learned to protect against the "knee giving out" sensation the test reproduces by contracting opposing muscles. ("Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis"). Often with ACL injuries, other tissues and structures can be injured as well. One of the more significant findings recently has been bone contusions with ACL injuries. Look for research on the topic coming out soon!
Note: these tests should only be used by properly trained health care practitioners
References: Benjaminse A, Gokeler A, van der Schans CP. "Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis. The Journal of orthopaedic and sports physical therapy. May 2006; 36(5):267-288. Web. 09/04/2012.
Cleland JA, Flynn TW, Whitman JM. "User's Guide to the Musculoskeletal Examination Fundamentals for the Evidence-Based Clinician: Evidence in Motion"; 2008; 264.