The anterior cruciate ligament (ACL) is a crucial ligament for knee stability. It primarily prevents abnormal front & back movement of the tibia (leg bone) in relation to the femur (thigh bone).
How does the ACL tear?
The ACL does not tear without some form of an injury. These injuries may occur during sports, road traffic accidents or activities of daily living (slipping on a wet floor, jumping from a low height or even dancing) that result in a sudden change of direction (pivoting), jumping or landing awkwardly. In rare situations, minor twisting while walking on uneven surfaces may lead to ACL tears.
What happens when the ACL is torn?
A torn ACL may lead to an unstable knee that results in "buckling" on sudden change of direction. Buckling causes abnormal movement between the thigh bone (femur) & the leg bone (tibia). This leads to tears of the menisci (shock absorbing cushions between these bones) and the articular cartilage (protective lining of the joint) causing early arthritis. The aim of treatment is to prevent this abnormal movement either by surgery or in some cases physiotherapy and / or activity modification.
Arthroscopic view of a torn ACL
Arthroscopic view of same case after ACL reconstruction
What is the initial management of ACL tears?
It is advisable to see a Dr soon after the injury only to confirm the diagnosis. In the early phase, this will be done primarily through radiological investigations as the knee is too tender to examine completely.
In most ACL injuries there is immediate knee swelling, pain, limp and restricted movement. The management of this early phase is relative rest, ice application & protection of the knee by a rigid or flexible brace followed by graded physiotherapy (prehab). During this phase one needs to be careful on slopes, uneven surfaces and must avoid twisting movements (pivoting) and jumping. This will protect the knee from buckling that will further damage the knee.
Early surgery is performed ONLY if the knee is "locked" or unstable even during activities of daily living.
When is ACL surgery performed?
ACL surgery is performed once the knee is pain free, not swollen, the muscles around the knee stronger through targeted exercises (prehab) and knee bending is satisfactory. In some cases this may be sufficient to manage the instability and no surgery is needed. However, if there is persistent instability, surgery (ACL reconstruction) is recommended.
How is the ACL reconstructed?
ACL reconstruction is done arthroscopically (key hole surgery). Grafts from the patient (autograft) or rarely allografts(from cadavers) are used. Subtle injuries to the capsule or other ligamentous structures may be detected during arthroscopic evaluation done at the time of ACL reconstruction. These deficits need to be addressed to prevent failure of the reconstructed ACL. Some of these reconstructions include the ALL (anterolateral ligament) or the PLC (poster-lateral corner).