Anterior Cruciate (ACL)

The anterior cruciate ligament (ACL) is a 3-4cm long band of fibrous tissue that connects the femur (thigh bone) to the tibia (shin bone). It helps stabilise the knee joint when performing twisting actions. The cruciate ligament is usually not required for normal daily living activities, however, it is essential in controlling the rotation forces developed during side stepping, pivoting and landing from a jump.

The ACL is commonly injured whilst playing running ball sports or skiing. Whilst playing ball sports momentum is developed and upon attempting a pivot, landing from a jump or side step manoeuvre, the knee gives way. When skiing, rupture may occur at low or high speeds. Commonly the binding fails to release as the ski twists the leg resulting in a tearing sensation. Patients frequently hear or feel a snap, or crack accompanied by pain. Swelling commonly occurs within the hour, but is modified by ice or compression. Frequently pain is felt on the outer aspect of the knee as the joint dislocates. This dislocation may be felt to reduce with a clunk. Initial treatment of any knee ligament injury should consist of ice packs, compression bandages and crutches.

It is difficult to weight bear for several days, however, after seven to ten days the swelling settles and walking is possible with the joint gradually returning to full movement. By four weeks following injury the knee becomes almost normal. Patients who return to sport following injury usually notice a weakness or instability. Further episodes of instability result in multiple injuries to the cartilages and the joint surfaces. Damage to these structures eventually leads to osteoarthritis.

Why does Anterior Cruciate Ligament (ACL) fail to heal?

Unlike other ligaments about the joint, the ACL passes through the joint and is surrounded by joint fluid. Other ligaments heal by scar formation, however due to the unique location of the ACL the bleeding is uncontained, filling the joint, causing pain and swelling. The blood irritates the knee joint?s lining to produce synovial fluid. This fluid is designed to dissolve and prevent blood clotting within the joint. Without blood clot, scar tissue does not form. The result is that the ACL rarely heals in continuity.

What are the treatments for Anterior Cruciate Ligament (ACL)?

The goal of treatment of an injured knee is to return the patient to their desired level of activity without risk of further injury to the joint. Each patient’s functional requirements are different. Treatment may be without surgery (conservative treatment) or with surgery (surgical treatment). Those patients who have a ruptured ACL and are content with activities that require little in the way of side stepping (running in straight lines, cycling & swimming) may opt for conservative treatment.

Those patients who wish to pursue competitive ball sports, or who are involved in an occupation that demands a stable knee are at risk of repeated injury resulting in tears to the meniscus, damage to the articular surface leading to degenerative arthritis and further disability. In these patients, surgical reconstruction is recommended.

Conservative Treatment Conservative treatment is by physical therapy aimed at reducing swelling, restoring the range of motion of the knee joint and restoring full muscle power. Proprioceptive training to develop the necessary protective reflexes are required to protect the joint for normal daily living activities. As the cruciate ligament controls the joint during changes of direction, it is important to alter your sports to the ones involving straight line activity only. Social (non-competitive) sport may still be possible without instability as long as one does not change direction suddenly.

Surgical Treatment Patients who are unable (generally young adults) or those unwilling to lower their level of activity, are at risk of causing further damage to their knee should they return to sporting activity and are advised to undergo surgical reconstruction. Reconstruction involves placing a graft inside the knee by arthroscopic surgery (keyhole). A >90% success rate is normal with some deterioration over time depending upon other damage within the joint. Although ACL reconstruction surgery has a high probability of returning the knee joint to near normal stability and function, the end result for the patient depends largely upon a satisfactory rehabilitation and the presence of other damage within the joint. Advice will be given regarding the return to sporting activity, dependant on the amount of joint damage found at the time of reconstructive surgery. It is important to preserve damaged joint surfaces by restricting impact loading activity to delay the onset of degenerative osteoarthritis later in life.

In the surgery a graft will be harvested to use to reconstruct the torn ligament. Usually 2 of the hamstring tendons are taken, but sometimes other suitable graft choices are used. This will be discussed with you prior to the operation. The remnants of the torn ACL are removed with keyhole surgery and tunnels are made in the tibia (shin bone) and femur (thigh bone) to allow the graft to be positioned across the knee. The new reconstructed ligament is then fixed at both ends to secure it in place. There are different treatments depending on condition which Dr.Kevin yip will advise during the consultation, if there is a need for a treatment or surgery. For an appointment with Dr.Kevin yip please call +65 6471 2691(24hours).