The ACL (Anterior Cruciate Ligament) is a ligament that connects the lower end of the thigh bone (femur) to the top of the lower leg bone (tibia). This ligament is commonly injured in sporting activities and can be problematic because it does not heal well. The poor healing capacity of the ACL is due to the fact that it is bathed in synovial fluid (the fluid that is normally in the knee) and that it is not well vascularized (ie: the ACL does not have an abundant blood supply).
How it happens
ACL injuries occur most commonly in patients who play sports. They can also occur with other types of trauma, such as falls or motor vehicle accidents. The most common mechanism of ACL injury is a twisting or pivoting injury on the knee, where the foot remains planted and the knee twists. It also occurs commonly when landing from a jump, when the knee buckles or twists. The patient usually feels a “pop,” when the anterior cruciate ligament tears. The knee will also usually swell up within the first twenty-four to forty-eight hours.
How it feels
After the knee is injured and the ACL is torn, the knee will often feel very painful due to the ligament injury and the swelling. Patients often have difficulty walking after a tear of the anterior cruciate ligament. Patients may also feel knee instability after they tear their ACL. The knee may feel unstable early after the ACL injury, or in some cases, patients will feel instability after they recover from the injury to the anterior cruciate ligament.
How it is fixed
Patients who are very active and participate in cutting and pivoting sports, such as basketball, soccer, and football, will have a very high incidence of knee instability after an ACL injury. For these individuals, surgery is recommended to avoid the risk of future instability related to their anterior cruciate ligament, which can also lead to further meniscus and cartilage damage. For patients who do not participate in cutting and pivoting sports, non-operative management may be considered. This consists of physical therapy and strengthening. For patients who elect to undergo surgery, the anterior cruciate ligament is reconstructed with a tendon. The ACL reconstruction can be done either with a tendon from the patient’s own knee, or using an allograft (or transplant) from a donor.
ACL reconstruction is done as an outpatient procedure, meaning that the patient goes home the same day. After ACL reconstruction, a brace is used for a few days and then patients can walk with crutches. Knee motion is started the day after surgery, and most patients can walk normally within one month of the ACL reconstruction. After anterior cruciate ligament reconstruction, patients initially work on range of motion and strengthening and then start light jogging at three to four months after surgery. A full return to sports requires at least six months of recovery after the procedure. The vast majority of patients are able to return to their previous level of activity in sports following successful ACL reconstruction.