Doctors know there can be problems without repair of a torn anterior cruciate ligament (ACL). The knee can become unstable. The ACL helps hold the knee joint together and keeps the bones from sliding around.
In this study researchers used MRIs to measure the amount of forward slide of the tibia (lower leg bone) on the femur (thigh bone). In the normal adult, there may be a small amount of this motion. When too much slide is present, this movement is called anterior tibial subluxation or ATS.
The knees of 96 patients with deficient ACLs were measured. The authors found the amount of ATS increases the longer the knee remains unstable. And the more unstable the joint, the greater amounts of ATS were present.
Based on these findings, the authors advise surgeons to use landmarks on the tibia when making tunnels in the bone to repair the ACL. Using landmarks on the femur may not be a good idea. With ATS the femur may shift in relation to the tibia.
They also point out that a patient with ACL deficiency who does not have ATS will develop it over time. This is another reason to repair the torn ACL sooner than later.