Understanding Knee Deformities Caused by ACL Tears
When a complete tear of the anterior cruciate ligament (ACL) occurs in the knee, deformities become evident soon after the initial injury. These deformities manifest as swelling, bruising, asymmetry compared to the unaffected leg, and various physical differences between the healthy knee and the one with an ACL tear. Conversely, in cases where the ACL has been overstretched or has suffered a partial tear, these minor deformities may develop gradually if the ligament fails to heal adequately.
Assessing ACL Tears with the Lachman Test
One way to determine if an ACL tear has occurred is through the use of the Lachman test. This test involves examining the stability of the shinbone in relation to the knee. By performing the Lachman test, a doctor or therapist can assess whether the ligament is still intact.
During the test, the individual is lying down, and their injured knee is positioned at a 30-40 degree angle. The doctor or therapist will then hold the femur with one hand and grasp the lower leg at the top of the calf muscle with the other hand. They will apply a slight upward and outward pull on the lower leg, away from the knee.
If the ACL is torn, there will be a noticeable movement of the bone, indicating instability and separation from the knee. On the other hand, if the ACL is intact, there should be minimal movement within the knee joint.
It is important to note that the Lachman test should not be performed on individuals who have recently injured their ACL, as it may cause further damage or exacerbate the existing injury.