Understanding the Knee Joint
The knee is one of the strongest joint in your body. It is made up of the lower end of thighbone, the upper end of the shinbone, and the patella (kneecap). The ends where these bones touch each other are covered with a smooth covering called articular cartilage. This covering protects and cushions the bones as the knee moves through the entire range of motion.
The knee also contains two wedge-shaped shock absorbing gel pads called meniscus between your thighbone and shinbone. These tough and rubbery gel pads help cushion the joint and keep it stable. The knee joint also contains a thin lining of fluid secreting tissue called the synovial membrane which releases fluid that lubricates the cartilage and reduces friction.
Bones are connected to one another by ligaments. There are four primary ligaments in your knee. They act like strong pillars to hold the bones together and keep your knee stable.
Collateral Ligaments - These are found on the sides of your knee. The medial collateral ligament is on the inside and the lateral collateral ligament is on the outside. They control the abnormal sideways motion of your knee and brace it against unusual sideway movement of the knee joint.
Cruciate Ligaments - These are found inside your knee joint. They cross each other to form an "X" with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the abnormal back and forth motion of your knee.
The PCL is located near the back of the knee joint. It attaches to the back of the femur (thighbone) and the back of the tibia (shinbone) behind the ACL. The posterior cruciate ligament (PCL) is one of the less commonly injured ligaments of the knee.
The PCL is the primary stabilizer of the knee and the main controller of how far backward the shin bone or tibia moves under the thigh bone or femur. If the tibia moves too far back, the PCL can rupture. The PCL is made of two thick bands of tissue bundled together. One part of the ligament tightens when the knee is bent; the other part tightens as the knee straightens. This is why the PCL is sometimes injured along with the ACL when the knee is forced to straighten too far, or hyperextend.
The most common way for the PCL alone to be injured is from a direct blow to the front of the knee while the knee is bent. Since the PCL controls how far backward the tibia moves in relation to the femur, if the tibia moves too far, the PCL can rupture.
Sometimes the PCL is injured during an automobile accident. This can happen if a person slides forward during a sudden stop or impact and the knee hits the dashboard just below the kneecap. In this situation, the tibia is forced backward under the femur, injuring the PCL. The same problem can happen if a person falls on a bent knee. Again, the tibia may be forced backward, stressing and possibly tearing the PCL.
Other parts of the knee may be injured when the knee is violently hyperextended, but other ligaments are usually injured or torn before the PCL. This type of injury can happen when the knee is struck from the front when the foot is planted on the ground.
The symptoms following a tear of the PCL can vary. The PCL is not actually enclosed inside the knee joint like the ACL. So unlike an ACL tear, which swells the joint with blood, PCL injuries don't make the knee swell as much. The pain and moderate swelling from the initial injury will usually be gone after two to four weeks, but the knee may still feel unstable.
Most patients with a PCL injury have a feeling of stiffness and some swelling. Patients may also have a feeling of insecurity and giving way of the knee, especially when trying to change direction on the knee.
The symptom of instability and the inability to trust the knee for support are what requires treatment. Also important in the decision about treatment is the growing realization by orthopedic surgeons that long-term instability leads to early arthritis of the knee.
The history and physical examination is probably the most important tool in diagnosing a ruptured or deficient PCL. During the physical examination, the doctor will check to see if the tibia moves too far back on the femur. Tests are also done to see if other knee ligaments or joint cartilage have been injured.The doctor may order X-rays of the knee to rule out a fracture, however ligaments and tendons do not show up on X-rays. The magnetic resonance imaging (MRI) scan is probably the most accurate test.
Initial treatment for a PCL injury focuses on decreasing pain and swelling in the knee. Rest and mild pain medications can help decrease these symptoms. You need to use a brace and crutches at first to limit pain. Most patients are allowed to put a normal amount of weight down while walking with the brace once the initial discomfort subsides.
The decision regarding operative or non operative treatment depends on the severity of the tear, age of the patient, associated concomitant injuries in the knee and the activity less of the patient. Less severe PCL , old patients with sedentary lifestyle and no other injuries in the knee can be tears are usually treated with a progressive rehabilitation program.
Therapists treat swelling and pain with the use of ice and rest periods with your leg supported in elevation. Exercises are used to help you regain normal movement of joints and muscles. This includes the use of a stationary bike, gentle stretching, and careful pressure applied to the knee by the therapist.
Exercises are also given to improve the strength of the quadriceps muscles on the front of the thigh.
Patients may require a functional knee brace before performing any activities. These braces are designed to replace knee stability when the PCL doesn't function properly. They help keep the knee from giving way during moderate activity, but they can give a false sense of security and won't always protect the knee during activities that require heavy cutting, jumping, or pivoting.If you do not have surgery to reconstruct your PCL, you may be at an increased risk of future knee problems, including chronic pain, a decreased level of activity, and injury to other parts of the knee. However, surgery is also not a "quick fix," as it involves a recovery period and requires committing to rehabilitation program.
If the PCL alone is injured, nonsurgical treatment may be all that is necessary. However, there is increasing evidence that any residual knee instability due to a non-functioning PCL will lead to a long term wear and tear in the knee and eventual early onset of arthritis. When other structures in the knee are injured, young patients with high demand activities or when the symptoms of instability are not controlled by a brace and rehabilitation program, generally do better having surgery. The main goal of surgery is to keep the tibia from moving too far backwards under the femur and to get the knee functioning normally again.
The time between an PCL injury and surgical reconstruction depends upon how quickly the person recovers from the acute phase of the knee injury, but is often at least two to four weeks from the date of injury.
Surgery is not usually performed immediately after an PCL injury because this could cause excessive scar tissue (arthrofibrosis) to develop, which would limit knee motion. In most cases, surgery is delayed until the swelling has resolved and the person is able to bend and straighten the knee without difficulty. Using ice packs and elevating the knee above the chest can help to reduce swelling.
After the PCL is torn, it is not possible to repair the ligament. This is due to several factors, including a damaged blood supply to the ligament (blood vessels damaged during injury) and cells inside the synovial fluid (normal fluid in the knee), that prevent healing. During the surgical reconstruction most people are given regional anesthesia (anesthetizing only the surgical part) and sedation prevent pain.
To reconstruct the torn ligament, a piece of healthy tendon, called an autograft, is removed or "harvested" from another area in the leg. There are several common autograft sites in the body, including the patellar tendon, hamstring tendon, or rarely the quadriceps tendon. Another option is to use a tendon from a deceased donor, called an allograft. No one type of graft has been proven to be better than another
Once the grafts are harvest, prepared and measured, accurately measured and directed holes are drilled in the tibia and the femur to place the graft. These holes are directed so that the graft will run between the tibia and femur in the same direction as the original PCL. The graft is then pulled into position using sutures placed through the drill holes. Screws or metal implants are used to hold the grafts in the drill holes.
Most people do well after PCL reconstruction and have no major complications. However, complications rarely occur during surgery or during the rehabilitation period. The most common complications include:
During the first few days, the goal is to control swelling and pain after the surgery. Elevating your knee above your chest and applying ice are the best ways to do this. Most people use crutches to assist with walking for the first week or so after surgery, although you will likely be encouraged to begin bearing weight on the affected leg as soon as possible. (If your surgery was more extensive, your surgeon may recommend delaying weight bearing for a longer period.)
You will probably need to wear a brace that keeps your leg straight for few weeks after surgery. This brace protects your knee, but many surgeons recommend removing it to do gentle range-of-motion exercises beginning about three to five days after surgery along with stretching and strengthening exercises. Your surgeon will give you a detailed plan for the rehabilitation protocol to be followed upon discharge from the hospital. You are strongly advised to consult a physiotherapist to initiate the rehabilitation protocol.
The first few physical therapy treatments are designed to help control the pain and swelling from the surgery and regaining the muscle strength around the knee. Therapists will begin to focus on range of motion exercises around three weeks. As the rehabilitation program evolves, more challenging exercises are chosen to safely advance the knee's strength and function. The therapist take care to avoid letting the tibia sag back under the femur, as this can put strain on the healing graft.
You will probably need a progressive rehabilitation program for four to six months after surgery to ensure the best result from your PCL reconstruction. In the first six weeks following surgery, expect to see the physical therapist two to three times a week. If your surgery and rehabilitation go as planned, you may only need to do a home program and see your therapist every few weeks.
You will be able to gradually get back to your work and sport activities. Some surgeons prescribe the use of a functional brace for athletes who intend to return to their sport. These patients are usually advised to wait at least six to none months before returning to their sport.
It's important to keep in mind that everyone heals differently. While your surgeon can give you a general idea of how long your recovery will take and how you will feel at each stage, this can vary. It may help to keep in mind that even though the recovery can be challenging, especially in the early weeks, you will likely be back to most of your normal activities after about six months. Depending on your sport(s), it may take a bit longer to return to full participation.