When the Athlete Has a Posterior Cruciate Ligament InjuryMuch has been written about the evaluation and treatment of anterior cruciate ligament (ACL) tears. That's because they are the most common knee injuries among athletes. Though less common, injuries to the posterior cruciate ligament are just as important. In this review article, surgeons from the New York University (NYU) Hospital for Joint Diseases bring us up-to-date on the important features of PCL injuries in athletes.
To better understand how PCL knee injuries occur, it is important to understand some of the anatomy of the knee joint. Knowing how the ACL and PCL work together to maintain stability and normal function is a large part of determining the optimal treatment for each patient.
The ACL and PCL are the two main ligaments that criss-cross and stretch between the femur (thigh bone) and the tibia (lower leg bone). These two bones join together to form the knee joint. Working together, the two cruciate ligaments control the back-and-forth motion of the knee.
The ACL keeps the tibia from sliding too far forward in relation to the femur. The PCL is made up of two separate but adjoining bundles of fibers. Each bundle has its own specific function. These bundles work together to keep the tibia from sliding too far backward in relation to the femur. They also control how much the tibia rotates externally (outward direction). Besides the ACL and PCL, there are other ligaments, cartilage, and soft tissues that surround the knee to help give it strength and stability.
There are two ways the PCL gets injured most often. The first is in a car accident when the passenger slams his or her bent knees into the dashboard on impact. The force and speed of the knee against a solid object pushes the tibia back underneath the femur. In a high-velocity injury of this type, the shear force is enough to rupture the PCL holding the tibia in place.
A second mechanism of injury (more common with athletes) occurs when the foot is planted on the ground and the knee hyperextends. Hyperextension means the joint is as straight as it can be and then a force pushes it into even more extension or overextension, thus the term hyperextension.
When the patient gives either one of these histories, the physician directs his or her examination to test the PCL. Several tests are commonly used such as the posterior drawer test, posterior sag, and the reverse pivot shift. The examiner will also check knee motion, quadriceps muscle function, and compare external rotation of the legs (the Dial test). The authors review each one of these tests (how to do them, what to look for, how valid and reliable they are).
Besides looking at the integrity of the posterior cruciate ligament, it's important to evaluate if there's been any damage to the blood vessels or nerves in the knee. Sensation, pulses, reflexes, and muscle strength will all be carefully reviewed.
Next, X-rays may be ordered. Any fractures or avulsion injuries can be seen on X-ray. An avulsion describes damage strong enough to pull a piece of bone away from the femur or tibia. The flat upper part of the tibia called the tibial plateau could also be fractured or damaged. Tibial plateau fractures are also visible on X-rays. Sometimes it can be difficult to tell if the PCL is partially or fully ruptured. Additional X-rays called stress radiographs and/or MRIs may be ordered for further clarification of the extent of damage.
Once the diagnosis has been made, then a plan of care must be determined. The severity of the injury usually guides who has surgery and how soon. For example, patients with avulsion injuries usually have surgery right away. The loose fragment of bone is screwed or stitched back in place with sutures.
Many players are actually able to participate in their sport with PCL-deficient knees. And they do so until the end of the season before considering surgery to reconstruct the knee and restore full stability. This is more likely to work when there is a partial tear, rather than a complete rupture. Undamaged supporting structures make it possible to continue functioning without a completely intact PCL. Keeping a strong quadriceps muscle is the key to successful recovery without surgery for mild PCL injuries.
Surgery is recommended when there is a chronic problem with pain and instability (e.g., the knee gives way under the leg). Instability because of multiple soft tissue injuries is more likely to cause enough problems to require reconstructive surgery. There are several methods used to reconstruct a ruptured PCL. The authors describe the transtibial approach, the inlay approach, the single bundle technique, and the double bundle technique.
Each of these surgical techniques was developed to overcome a specific problem or complications from one of the other approaches used. Some methods attempt to mimic the natural anatomy (e.g., double bundle reconstruction). Others, such as the single-bundle approach don't try to reconstruct both bundles of the natural PCL.
Many surgeons prefer the double-bundle technique because it prevents posterior tibial translation better than a single-bundle approach. The double bundle reconstruction also shares the full load placed on the knee from all angles and through the full range-of-motion. But there are still some details to work out on the best placement of each bundle to mimic the tension placed on the knee by the intact PCL.
No matter what type of reconstruction is performed, there is always the risk of problems after surgery. The most common complication is a relaxation of the tendon graft used to replace the ruptured PCL. Because tendon harvested from someplace else in the knee is used to rebuild the PCL, there is more give than ligament and a greater chance of stretch.
A less common but more serious problem is damage to the nerves or blood vessels of the knee. Infection, osteonecrosis (bone death), chronic pain, and problems with any hardware used are also potential problems.
The authors conclude by saying that the fact that some athletes can recover without surgery tells us there's much we don't know about how the PCL works and which injuries don't need surgery. Long-term studies are needed to show what happens for athletes with different degrees of PCL injury when treated with and without surgery.
The only way we will know how to advise patients about the best course of treatment is to follow injured athletes over decades to see what happens years later. Do they develop arthritis? Are both sides of the joint affected equally? Finding the optimal reconstruction technique for best possible outcomes is another long-term goal.
Alexis Chiang Colvin, MD, and Robert J. Meislin, MD. Posterior Cruciate Ligament Injuries in the Athlete. Diagnosis and Treatment. In Bulletin of the NYU Hospital for Joint Diseases. March 2009. Vol. 67. No. 1. Pp. 45-51.
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