The anterior cruciate ligament (ACL) is 1 of the 4 main ligaments responsible for providing stability to the knee. Unfortunately, the ACL is commonly injured during pivoting sports like soccer, netball, basketball and floorball. It can also occur from accidental fall or traumatic injuries, a common example being a ski injury.
Unlike the collateral ligaments (MCL & LCL) that are located outside the knee joint, the ACL resides within the knee joint itself and has a poor blood supply. As a result, ACL tears typically do not heal well. When they do heal, they often heal with laxity, and hence patients with ACL injuries tend to experience instability of their knee if left untreated.
Typical Symptoms & Signs of ACL injury
Patients with ACL injury typically present with acute pain and rapid swelling of their knee after a twisting or pivoting injury. A typical injury mechanism will be an athlete trying to push off and change direction with the injured leg planted on the ground, causing a twisting force across the knee joint, and the ACL. They may hear a ‘pop’ sound. Another common injury mechanism occurs during skiing when the ski gets caught in the snow without uncoupling from the ski boot, and the momentum of the falling skier causes a huge twisting force across the knee joint.
Examination of the injured knee usually reveal a notable swelling, although swelling can be minimal in partial ACL injuries, or when the patient presents late (weeks or months later after the initial injury). The patient may also have a limited range of motion of the knee, and there will usually be notable laxity on examination of the knee. Many a time, an ACL injury can be diagnosed clinically, from the history of the injury and the clinical examination.
MRI scan is often used to confirm the diagnosis and to look for associated injuries such as a meniscal tear or cartilage injury, that may warrant early treatment. MRI is also useful for partial ACL injuries to determine if surgery is needed, or if the injury can be treated non-operatively.
Conservative Treatment for ACL Tear
Conservative treatment is usually reserved for older or less active patients, who do not intend to engage in more physically demanding sports and activities. Partial ACL tears with minimal knee instability will be another suitable reason for non-operative management.
Bracing may be utilized to provide interim stability. In the initial few weeks of the injury, a pair of crutches may also be helpful to offload the affected knee.
Physical therapy is often recommended if non-operative management is pursued. In the acute phase soon after the injury, physiotherapy can help to reduce swelling and pain, improve range of motion, and restore walking ability. Once the acute pain and swelling have resolved, strengthening and balancing exercises can help to improve knee stability and hopefully avoid the need for surgery.
Surgical Treatment for ACL Tear
Surgery for ACL injury, unfortunately, does not entail repairing the torn ligament as the ligament has poor blood supply and thus limited healing potential, making the successful healing of a ‘repaired’ ligament difficult. Very recently, successful techniques to repair the ACL have been developed, but only a selected group of patients with an ACL injury will have a good chance of success with ACL repair (see advances in ACL surgery).
Most patients with a complete ACL injury who wants to continue to engage in sports will likely require an ACL reconstruction. This essentially entails creating or reconstructing a new ligament. This is, fortunately, a simple and straightforward surgery and is performed with the use of an arthroscope (key-hole surgery). It is typically done as a single day surgery procedure under general anaesthesia, with the patient being able to ambulate with limited weight on the operated leg using a pair of crutches immediately after surgery.
During this key-hole surgery, the torn ACL is replaced with a newly reconstructed ACL graft. The most common source for the graft is one’s own hamstring tendons, although other common graft options would be the patient’s own patella tendon (common amongst soccer players and contact athlete), or the use of an allograft (donor tendon). Our surgeons will discuss and advise you on the most suitable graft option for your reconstruction based on your age, activity level, and your personal preference.
Arthroscopic ACL Reconstruction Surgery
It typically takes an arthroscopic surgeon about 1 to 1.5 hours (depending on the extent of the associated injuries) to perform this surgery. Once under anaesthesia, your surgeon will sterilize the operation site and harvest the hamstring tendons via a 2 to 3 cm incision on your upper shin (not needed if an allograft is utilised) The arthroscope and other minimally invasive instruments will then be introduced into the knee joint via 2 small sub-centimetre key-hole incisions on the front of the knee.
The meniscus tears and cartilage are then inspected for concomitant injuries, and if present, these accompanying injuries will be addressed in the same setting. Attention will then be turned to the injured ACL itself and the torn ACL will be removed with an arthroscopic shaver, whilst preserving any healthy remnant fibres that will aid incorporation of the graft to the knee. This ‘remnant preservation’ reconstruction technique is typically utilised for the majority of our ACL reconstructions.
Bone tunnels are drilled into the tibia (shin bone) and the femur (thigh bone) at the native location or footprint of the original ACL (Anatomic ACL reconstruction), to replicate the normal anatomy of the injured ligament. These tunnels are created using the 3 minimally invasive incisions previously described, without the need for any additional incisions.
The prepared ACL graft is then pulled up through the tibia tunnel, into the knee joint, and finally into the femoral tunnel with the help of tractions sutures.
The graft is held under tension as it is fixed in place using minimally invasive fixation devices. These devices used to hold the graft in place are inert and harmless when left in the human body, and generally, are not removed even after complete recovery from the surgery.
Postoperative recovery and rehabilitation after ACL Reconstruction
The patient usually goes home on the same day of the surgery, or the day after surgery once pain control is achieved and the patient is able to move about comfortably and confidently with the aid of a pair of crutches.
Upon discharge from hospital, the wound is kept clean and dry with sterile dressings for the 1st 2 weeks after surgery, and the emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control in the first 10 to 14 days after surgery,
The knee is iced regularly to reduce swelling and pain. Weight-bearing status (use of crutches to limit the amount of weight applied onto the operated leg) is determined by your surgeon, based on the accompanying injuries and the intra-operative findings, but generally most patients will be utilising crutches for the 1st 4 to 6 weeks with progressive increase in walking ability, before going completely without crutches.
Post-operative physiotherapy is crucial for a successful outcome of this procedure, and your surgeon will link you up with a physiotherapist experienced in post-operative ACL reconstruction rehabilitation within the 1st 2 weeks of your surgery. Pre-operative physiotherapy may occasionally be required for significantly stiff and swollen knees but is otherwise usually started after surgery.
Most patients will start jogging about 4-6 months after surgery. The return to pivoting sports or high demand activities such as soccer and netball usually takes an average of 9 months, but this ability to return to sports is variable and dependent on many factors, including the type of sports, the level of participation, the extent of the injury, as well as the patient profile.
With advances in our surgical techniques and the minimally invasive methods we utilise, our patients are recovering faster as a result of the accelerated rehabilitation protocols being utilised. Nevertheless, we emphasize again the importance of regular physiotherapy as well as clinical reviews to achieve a successful outcome.
For more information on ACL injuries and surgical treatment, please consult our arthroscopic sports surgeon.