The posterior cruciate ligament (PCL) is the strongest and largest intra-articular ligament in the human knee and the primary posterior stabilizer of the knee. It comprises 2 functional bundles: the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB).
The PCL originates from the anterolateral aspect of the medial femoral condyle within the notch.
The PCL inserts along the posterior aspect of the tibial plateau, approximately 1 cm distal to the joint line.
The middle geniculate artery perforates the posterior capsule running parallel to the superior edge of the synovial septum. It has branches to the synovium around the PCL forming a plexus of vessels supplying the PCL. There is also a potential supply from a branch of the inferior geniculate artery.
The tibial and obturator nerve has posterior articular branches to the posterior capsule. These branches perforate the posterior capsule to reach the PCL.
The PCL functions as one of the main stabilizers of the knee joint and serves primarily to resist excessive posterior translation of the tibia relative to the femur. The PCL also acts as a secondary stabilizer of the knee preventing excessive rotation specifically between 90° and 120° of knee flexion. The two bundles of PCL, ALB and PMB function synergistically.
- Classic “dashboard injury”-posteriorly directed force on the anterior aspect of the proximal tibia with the knee flexed.
- Direct blow to the anterior tibia or a fall onto the knee with the foot in a plantar flexed position.
- Mostly seen in Football, soccer, rugby and skiing are among the sports with highest incidence of PCL tears.
- Stiffness, swelling and pain on the posterior aspect of the knee are typical symptoms.
- Anterior knee pain and instability when descending stairs are more often associated with chronic isolated tears.
- Incidence – Posterior cruciate ligament (PCL) tears comprise 3% of outpatient knee injuries and 38% of acute traumatic knee hemarthroses. These injuries rarely occur in isolation, and up to 95% of PCL tears occur in combination with other ligament tears.
Assessment of PCL Injury
- Acute PCL injuries present with joint swelling and about 10° to 20° of restriction in further flexion due to pain.
- Chronic PCL injuries may present with limited activity such as having difficulty in climbing slopes due to lethargy and pain in the anterior and medial areas of the knee rather than instability.
- Posterior drawer test – Most accurate test for PCL injuries. At 90° of knee flexion, posterior sagging of the tibia is observed on the affected side.
- Grade I: The PCL has a partial tear.
- Grade II: The ligament is partially torn and is looser than in Grade I.
- Grade III: The ligament is completely torn and the knee becomes unstable.
- Grade IV: The PCL is damaged along with another ligament in the knee.
Arthrocopic findings (definitive diagnosis)
Arthroscopy is a type of operation where a small fiber-optic TV camera is placed into the knee joint, allowing the surgeon to look at the structures inside the joint directly. The vast majority of PCL tears are diagnosed without resorting to this type of surgery, though arthroscopy is sometimes used to repair a torn PCL.
- Initial treatment for a PCL injury focuses on decreasing pain and swelling in the knee. Rest and mild pain medications, such as acetaminophen, can help decrease these symptoms. You may need to use a long-leg brace and crutches at first to limit pain.
- Most patients receive physical therapy treatments after a PCL injury. Therapists treat swelling and pain with the use of ice, electrical stimulation, and rest periods with your leg supported in elevation.
- Exercises are used to help you regain normal movement of joints and muscles.
- The symptoms of instability are not controlled by a brace and rehabilitation program, then surgery may be suggested.
- 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.
Arthroscopic PCL Reconstruction
1. Most PCL surgeries are now done on an outpatient basis, and most patients stay either one night in the hospital, or they go home the same day as the surgery.
2. In a typical surgical reconstruction, the torn ends of the PCL must first be removed. Once this has been done, the type of graft that will be used is determined. One of the most common tendons used for the graft material is the patellar tendon.
About one third of the patellar tendon is removed, with a plug of bone at either end. The bone plugs are rounded and smoothed. Holes are drilled in each bone plug to place sutures (strong stitches) that will pull the graft into place. Then holes are drilled in the tibia and the femur to place the graft. These holes are placed 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 are used to hold the bone plugs in the drill holes.
3. Another very common graft involves using two of the three or four strips, the graft has nearly the same strength as a patellar tendon graft.
The gracilis and semitendinosus tendons can be taken out without really affecting the strength of the leg because bigger and stronger hamstring muscles will take over the function of the two tendons that are removed.
4. Allograft – An allograft is tissue that comes from someone else. This tissue is harvested from tissue and organ donors at the time of death and sent to a tissue bank. The advantage of using an allograft is that the surgeon does not have to disturb or remove any of the normal tissue from your knee to use as a graft. For this reason the operation also usually takes less time.
Return to Work/Sports
- You wear a protective knee brace for two to three weeks after surgery. You’ll use crutches for two to four weeks in order to keep your knee safe and will probably be instructed to put only a limited amount of weight down while you’re up and walking.
- Therapists will begin to focus on range of motion exercises within three weeks. They take care to avoid letting the tibia sag back under the femur, as this can put strain on the healing graft.
- Strengthening exercises for the quadriceps muscle.
- When you get full knee movement, your knee isn’t swelling, and your strength is improving, you’ll be able to gradually get back to your work and sport activities.
- Ideally, you’ll be able to resume your previous lifestyle activities. However, athletes are usually advised to wait at least six months before returning to their sport.
Complication – Preoprative – Rare
- Popliteal artery injury
- Osteonecrosis of medial condyle of femur
- Tibial fracture
- Tourniquet – compartment syndrome
- Muscle injury, nerve injury, dvt, co-agulopathy
- Anterior knee pain
- Painful hardware
- Heterotopic ossification(HO)