By Erik C. Johnson, M.D.
The knee is a complex joint with four major ligaments. The anterior cruciate ligament (ACL) is a strong band of tissue that is located within the knee and connects the thighbone (femur) to the shinbone (tibia). It functions to provide stability to the knee joint. In the past, an ACL tear was a career-ending injury. With today’s surgical techniques and rehabilitation protocols, many athletes return to the athletic field without problems.
Injuries to the ACL are among the most common of all sports-related knee injuries. It is estimated that each year in the United States between 200,000 and 300,000 people sustain a torn or ruptured ACL. Young people (age 15-25) who participate in cutting and pivoting sports, such as basketball, football, and soccer, are especially vulnerable to ACL tears. NCAA injury data show that female athletes injure the ACL four times more frequently than their male counterparts.
The ACL is injured by direct blows to the knee, which commonly occurs in football or a fall when skiing. In these scenarios, the knee is forced into an abnormal position that results in the tearing of one or more ligaments. In addition, the ACL may also be injured in non-contact situations. Such injuries happen when the athlete is planting the foot and cutting, landing on a straight leg, or making a quick stop. These maneuvers are common in basketball, volleyball, football and soccer.
When the ACL is torn, you will feel the knee give way often associated with a loud pop. There is usually instant pain. Over several hours, the knee becomes swollen and walking becomes difficult. The swelling and the pain are the worst for the first two days after the injury and then decreases. After the pain and swelling resolve, patients complain of episodes of instability, or giving-way. The knee often times feels loose.
A diagnosis of ACL injury is based on a thorough history and physical examination of the knee. Frequently, the knee is too swollen and painful to perform a complete physical exam within the first week of injury. X-rays will not show a torn ACL, but are taken to evaluate the bones and any associated fractures. Magnetic resonance imaging (MRI) is ordered to look at the ligaments, tendons, and cartilage.
The decision-making process of whether or not to reconstruct the ACL is based on many factors. The final decision is made on an individual basis. The decision depends on your age, activity level, how unstable the knee feels, if it is a complete or partial tear, if there are associated injuries (other ligaments, cartilage, or meniscus), and what your expectations are. Both operative and non-operative treatment choices are available. Non-operative intervention involves activity modification in combination with physical therapy. The best chance to have a stable knee and an active lifestyle without further pain or injury will be ACL reconstruction followed by rehabilitation. Usually athletic individuals choose surgery to allow them to return to their respective sports and hobbies. ACL reconstruction involves replacing the torn ACL with strong, healthy tissue taken from another area in the knee. A strip of tendon from under the kneecap (patella tendon) or hamstrings may be used. The healthy tissue is threaded through the inside of the knee replicating the original ACL. After surgery, physical therapy helps rebuild flexibility as well as strength to the lower extremity. As with any surgery, youll want to consider some potential complications before deciding on ACL reconstruction. The most frequent complications include pain in front of the knee, loss of motion, and occasional swelling.
Successful ACL reconstruction surgery tightens your knee and restores stability. It also prevents further injury to the other structures such as the articular cartilage and meniscus. Over 250,000 ACL reconstruction surgeries are performed each year, making the procedure the sixth most common orthopaedic procedure performed. With current surgical techniques and post-operative rehabilitation protocols, 85-90% of patients are satisfied with their surgery and return to sporting activities without instability.
Frequently asked questions?
How long will it take to return to high-demand sports such as basketball and football?
For the average recreational athlete, it usually takes about 6-9 months to return to full activity.
How do you know if you have torn your ACL?
The best way to diagnose an ACL tear is by having the doctor perform a thorough history and physical exam. If there is still any doubt, a MRI will help provide additional information.
Who needs their ACL reconstructed?
The most frequent indication to perform ACL surgery are those individuals that want to return to twisting, turning, and jumping sports that have an unstable knee.