An injury to the ACL or anterior cruciate ligament is one of the most common and dreaded knee injuries among athletes participating in sports that require quick stops, starts, cutting, twisting, jumping and collisions. ACL injuries can occur to athletes of all ages and levels of sport from the youth athlete to the professional. The ACL is one of four main ligaments of the knee that work to stabilize the knee during athletic motions of the knee. Think of the ACL more than any of the other ligaments in the knee as the safety belt in your knee that prevents your shin bone or tibia from sliding forward and rotating excessively during your sporting activity.
Mechanism of Injury
Many people associate an ACL tear with a contact injury such as clipping in football or a slide tackle in soccer. While this type of trauma to the knee can certainly result in a traumatic tear of the ACL, in fact the majority of ACL tears occur as a result of non contact injuries. This occurs due to rapid decelerations or twisting of the knee which may occur when landing from a jump, or cutting and rotating the upper body on a planted foot. While the athlete has done this maneuver thousands of times, unfortunately this time due to the magnitude and direction of the force on the knee the ACL can tear. These mechanisms are common in sports that involve cutting and pivoting, such as soccer, football and lacrosse, as well as sports that involve jumping, such as basketball, volleyball, and cheerleading.
Diagnosis
Many athletes that injure their ACL will describe feeling or hearing a loud pop in the knee. A complete tear of the ligament usually causes the knee to become very swollen, often within minutes. Bearing weight on the injured leg is often very difficult. Return to the game or practice is usually not possible due to the pain immediately after the injury.
In most cases, the knee injury is severe enough for athletes to seek medical attention. A trainer or physician often can examine the knee before significant swelling has developed and the athlete starts to guard and protect the knee from abnormal movements. In this scenario, the diagnosis of a torn ACL can be made simply by physical examination of the knee. The tibia can be shifted out from under the femur or the knee can be made to buckle in certain positions.
After a few hours, diagnosis of an ACL injury becomes more difficult. Once the knee is significantly swollen and the athlete resists examination of the knee due to pain, physical examination alone is less effective, even in the emergency room or orthopaedic surgery clinics. A sports medicine surgeon will take a thorough history to determine the mechanism of injury. He or she will attempt to perform a physical exam to assess the integrity of the ligament. X-rays are often taken to look for fractures or secondary signs of injury to the ACL. Often an MRI is requested in order to most accurately diagnose the injury and associated injuries in a timely manner.
If the athlete does not seek immediate medical attention they may be unaware of the severity of the injury. Usually the swelling and pain will resolve and normal activities of daily living are tolerated quite well. The knee may even feel normal. However, attempts to go back to sports that require cutting, jumping and twisting may result in a second episode of giving away. This can cause even more damage to the knee and secondary structures such as the meniscus, articular cartilage, or other ligaments since the ACL (safety belt of the knee) was not present to protect the knee.
ACL tear
A complete tear of the ACL does not typically heal. This fact does not necessarily mean that every patient with this injury needs to have surgery. The problem with a torn ACL is not pain, stiffness, or swelling, although these are usually present initially. Eventually with ice, compression and elevation, and rehabilitation to restore strength and motion, the swelling, pain, and motion will improve. The problem with a torn ACL is a lack of stability of the knee. Athletes who perform cutting and pivoting sports or jumping sports often cannot return to sports after this injury due to the fact that their knees will buckle trying to compete. These athletes almost always need surgery to return to sports. Older athletes, especially those who are active but don’t participate in these types of sports, might be able to return without surgical treatment. Custom braces made to prevent the knee from giving way can be helpful in this population.
Surgery
The goal of surgery is to restore the stability of the knee and allow normal function without predisposing the knee to arthritis or secondary problems. The torn ligament is not sewn back together or repaired since this typically did not restore stability when it was tried in the early years of ACL surgery. Therefore the ligament is in fact reconstructed. Normally tissue is borrowed from another location in the same knee and this is used as a graft to create a new ACL. Traditionally the middle third of the patellar tendon in front of the knee was used along with a cylinder of bone from the patella and tibia. Other common grafts used are the tendons of the medial hamstrings. In the United States hamstring grafts and patellar tendon grafts are used with similar frequency with similar results and no significant increased risk of rerupture between the two techniques. However, since they come from different locations about the knee, they have there own individual positives and negatives. Donor grafts from a cadaver are also used but should be reserved for older patients with less strenuous athletic goals because they have been found to have a significantly higher failure rated in young high level athletes. In all ligament reconstructions the goal is to have a strong graft, put it in the knee in the right place, avoid potential stress risers to the graft, tension it appropriately, and fix it on each end with rigid fixation to the bones of the femur and tibia to allow early rehabilitation. Discuss the graft options with your doctor to determine which graft is best for you. Ultimately, regardless of the graft you choose, with successful surgery and rehabilitation, you should have an excellent result.
The surgery is done primarily with the arthroscope and takes about 90 minutes. At the time of surgery the knee is thoroughly evaluated for additional injuries such as meniscal or cartilage damage. The procedure is done as an outpatient, and the patient is asked to stay at home for a period of time after surgery to work on elevation, icing, range of motion exercises and isometrics to begin the rehab process and avoid complications. Oral pain medicine is provided. Formal physical therapy is usually begun within 10 to 14 days after surgery. How much weight the patient can put on the leg depends on the status of other structures in the knee, especially the meniscus, as well as the preference of the surgeon. Similarly your surgeon may provide a brace for additional support.
Rehabilitation
The goal of ACL surgery again is to create a stable functional knee that is able to go back and participate in physical activities without recurrent episodes of giving away.
Other than the quality of the actual surgery, no other intervention is more crucial to a successful outcome than physical therapy. Working with a physical therapist who specializes in sports injuries can make a difference in the success of returning to sports. The rehab process starts almost immediately, with the athlete going to therapy 2-3 days per week initially to work on regaining range of motion. Our first goal is to get full extension and our second goal is to obtain full flexion. Once range of motion is obtained the goal is to restore strength. As the knee gets stronger, the therapist will often implement sport-specific functional training to get the knee ready to return to sports. A test to determine the muscle strength at various speeds may be performed to help determine if the knee and surrounding muscles are strong enough to resist forces encountered in sports. The rehabilitation process is lengthy and difficult, but it is crucial to the athlete returning to the same or higher level of sports.
Custom knee brace
In certain athletes, a custom knee brace can help the athlete when he or she returns to sports.While braces have not been proven to prevent repeat ACL tears, they can improve biofeedback and confidence especially early on when returning to sport.
Return to Sports
The success rates of returning to the sport that the athlete played are very high, usually noted be more than 90%. However recent information regarding NFL athletes showed only a 63 % rate of returning to the NFL after ACL reconstruction. The average time to being cleared for sports participation is about six months, but this time can be longer depending on return of motion and strength and being able to perform the sport-specific functional duties on the reconstructed knee.
Risks of ACL Surgery
As in all surgeries there is a risk of infection due to the violation of the skin. While this is rare in ACL surgery, your surgeon will use specialized solutions to help sterilize your knee in the OR prior to surgery, and he or she will give you antibiotics through your IV immediately prior to the operation. Excessive bleeding after ACL reconstruction is rare but bruising is common and may be extensive. The risk of blood clots exists due to the decreased activity so it is recommended that the patient take one adult aspirin daily. Stiffness is also a risk so it is imperative that the patient perform their daily rehab activities and work with a therapist trained in ACL rehabilitation. Lastly there is a risk of rerupture of the ACL graft which may occur at any time once the patient returns to sport. This rate of rerupture ranges from approximately 5 % to as high as possibly 25 % in male athletes less than 18 years old. We are continually analyzing our results and techniques to improve the long term success of this surgery.