From the Research
To perform the Lachman test on a large individual, it is recommended to modify the technique by using alternative positions or assistance to ensure accurate assessment of anterior cruciate ligament (ACL) integrity, as the standard method may be challenging due to the patient's size. When performing the Lachman test, place the patient's knee in 20-30 degrees of flexion while they lie supine on the examination table. For better control, sit beside the patient's thigh and stabilize their femur with one hand, considering the use of your forearm for larger thighs, while your other hand grasps the proximal tibia 1. Pull the tibia forward with a firm, quick motion while keeping the femur fixed. A positive test is indicated by excessive anterior translation of the tibia relative to the femur and/or a soft endpoint (compared to the solid endpoint felt in an intact ACL).
The Lachman test is a crucial examination for assessing ACL injuries, with high specificity for ACL pathology, as noted in a comprehensive clinical examination guide 2. However, for very muscular or obese patients, alternative positions such as having the patient sit with their leg hanging off the table edge or recruiting an assistant to help stabilize the limb may be necessary to ensure an accurate assessment. The reliability and diagnostic accuracy of the Lachman test, even in alternative positions like the prone position, have been established, showing it to be a reliable evaluation technique for confirming the presence of an ACL tear 3.
Key considerations for performing the Lachman test on a large individual include:
- Modifying the technique to accommodate the patient's size
- Using alternative positions or assistance when necessary
- Ensuring proper stabilization of the femur and tibia
- Performing the test with a firm, quick motion to assess ACL integrity accurately
- Being aware of the test's limitations and the potential need for additional diagnostic assessments.