Posterior Cruciate Ligament Tear: Causes, Symptoms & Treatment

A tear of the posterior cruciate ligament is an accidental injury. It occurs relatively rarely and is often detected late. Accurate diagnosis is therefore important to avoid subsequent damage.

What is a posterior cruciate ligament tear?

The posterior cruciate ligament is the thickest and most important ligament in the knee joint. It ensures that the lower leg does not slide behind the thigh bone at the base of the knee joint. A posterior cruciate ligament tear is much less common than an anterior cruciate ligament tear because of the position and thickness of the ligament. Because a great deal of force is required for this injury, a tear of the posterior cruciate ligament rarely occurs in isolation. It is usually accompanied by other injuries to the knee and can therefore be easily overlooked and then remains untreated. In this case, the originally acute injury can take on a chronic course. This can cause secondary damage.

Causes

Tears of the posterior cruciate ligament occur when the maximum possible stretch of the ligament is exceeded. Often, this happens in so-called rasan trauma, which refers to injuries in which a sudden strong force is applied to the knee. This can happen in motorcycle, bicycle or car accidents. From car accidents, the phenomenon is known that the impact of the knee against the dashboard pushes the lower leg backwards, which can cause a tear in the posterior cruciate ligament. However, this is increasingly rare as a cause of injury. Far more common is a posterior cruciate ligament tear as a result of a sports injury, such as a fall on the bent knee or impact trauma from an opponent, as is more common in American football. Here, further injury to the knee often occurs to the joint capsule or other ligaments.

Symptoms, complaints and signs

A posterior cruciate ligament tear is sometimes manifested by a distinct cracking or tearing sensation. Patients often experience a feeling of displacement in the knee, accompanied by an unusual sensation of pressure. This is followed by severe pain, which, however, subsides after a few minutes. As the condition progresses, the pain occurs mainly when weight is placed on the affected leg. When climbing stairs or doing knee bends, the discomfort is usually strongest, which is why affected persons usually adopt the typical, slightly bent posture with the knee. The knee swells, which can result in restricted movement. The injury to blood vessels causes a bruise to form in the area of the joint, but this quickly subsides. In the first few days after the injury, the knee feels unstable and cannot be moved as before. A cruciate ligament tear is not always noticed immediately by the person affected. Sometimes the injury is first manifested by an increasing unsteadiness of gait and a pulling sensation in the knee. In addition, the knee buckles away even under low stress. Generally, a posterior cruciate ligament tear causes generalized knee pain that can radiate to the upper and lower leg or even to the foot, depending on the severity of the injury.

Diagnosis and course

Schematic diagram of healthy cruciate ligaments and the various forms of cruciate ligament tears. Click to enlarge. Because a tear of the posterior cruciate ligament occurs comparatively rarely and is usually accompanied by numerous concomitant injuries due to the force required for it, it is easily overlooked. For this reason, a particularly thorough diagnosis is important in the case of knee injuries. The affected knee is usually swollen and non-specifically painful. Bruising may be visible. A description of how the accident occurred provides initial information about the extent and type of damage to the knee, and a careful examination of the knee joint with special tests is also essential. Accompanying injuries of the inner and outer ligament apparatus should be checked, including cruciate ligament injuries and tears of the inner or outer ligaments. The so-called posterior drawer is checked; this involves pushing the lower leg back against the thigh. X-ray examination and magnetic resonance imaging (MRI) are also part of the diagnostic process. To measure the extent of drawer motion of the lower leg, functional X-rays, called held radiographs using an apparatus designed for this purpose, may be useful. However, even with an MRI, a tear of the posterior cruciate ligament may be difficult to detect because the ligament has a relatively good blood supply.An injured ligament can also heal on its own, but then usually remains extended. The resulting instability of the knee can become chronic in this way. As a result of the incorrect movement, cartilage damage occurs, which can lead to osteoarthritis in the knee within a few years.

Complications

In many cases, unfortunately, there is a delayed diagnosis of this injury, which is why a complete recovery is often not possible. The cruciate ligament rupture often causes severe pain in the knees. This pain often spreads to other regions of the body and can also lead to sleep problems at night in the form of pain at rest. The knee is not infrequently swollen and affected by a bruise. Often the knee is also unstable, so that heavy physical work or sports can no longer be performed by the patient without further ado. The quality of life of the affected person is considerably limited by the cruciate ligament rupture. Gait insecurities continue to occur and the affected person not infrequently adopts a gentle stance, which, however, has a negative effect on health. Likewise, the pain and limitations can lead to psychological discomfort and possibly depression. The treatment of this complaint is usually carried out through therapy or with the help of a surgical intervention. Furthermore, no particular complications occur. However, a positive course of the disease is not always possible, so that the affected person may suffer from restrictions throughout his life. Possibly, the performance of certain sports is then no longer possible. There is no reduction in life expectancy.

When should you see a doctor?

If sudden discomfort, a cracking sound and problems with locomotion occur within movement sequences, the leg should be immobilized. The discomfort occurs around the knee and can occur during sports activities as well as everyday movements. A doctor is needed for a cruciate ligament rupture, but the affected person can already take some supportive measures on the spot, which have a positive influence on the further course. If possible, the leg should no longer be loaded and should be cooled until the medical examination. In case of swelling or discoloration of the skin, a medical clarification of the complaints is necessary. Clothing on the knee should be removed so that there is no feeling of tightness or problems with blood circulation. If there is pain, unsteadiness of gait or a loss of strength in the leg, there is cause for concern. Often, in a euphoric mood, sufferers realize belatedly that a torn ligament has occurred. They notice a wobbly feeling during usual movements and should see a doctor for a check-up. If there is sudden bruising, sensory disturbances or abnormalities with touch, a doctor’s visit is necessary. If stiffening of the knee sets in or the knee joint appears particularly unstable, a doctor is needed. People with knee disorders should be especially careful and not let time pass before seeking treatment.

Treatment and therapy

A tear of the posterior cruciate ligament is a relatively serious injury, but it usually heals well with conservative measures. In the course of such nonsurgical treatment, the knee is first immobilized in a special brace or stabilized with a splint that allows limited movement. This prevents the lower leg from sliding back against the thigh at rest or during movement. This splint is usually worn for about six weeks. The supporting muscles, especially in the thigh, are strengthened through physical therapy exercises. If the rest of the ligamentous apparatus is also affected, surgery is recommended. Similar to the more common anterior cruciate ligament rupture, the damaged posterior cruciate ligament is replaced by transplanting a tendon from the patient’s own body. However, the procedure is more complicated than in the case of anterior cruciate ligament rupture. The success of the operation depends not least on how carefully the follow-up treatment is carried out in order to avoid consequential damage such as restricted mobility or osteoarthritis in the knee. After the operation, a firmer splint must be worn for about six weeks, then a splint that allows initial movements. Accompanying lymphatic drainage is recommended, and precisely coordinated physiotherapy is absolutely necessary.After a longer period of rest for recovery, movement exercises are only performed passively in the first few weeks, and later the first weight-bearing exercises are added, which are increased very slowly. If the therapy is successful, the injury is considered healed after about half a year. After about a year, the leg can be fully loaded again. The extent to which certain sports can be performed or are recommended thereafter must be decided on a case-by-case basis.

Outlook and prognosis

The difficulty of the posterior cruciate ligament tear lies in the correct as well as rapid diagnosis. Often, the tear is overlooked or the existing injury is misdiagnosed. This leads to a delay in appropriate treatment and can trigger complications or problems with healing. If the tear is documented promptly after the accident or fall in a comprehensive and thorough diagnostic evaluation, a full recovery can be achieved with optimal medical care. Normally, the patient gets a good prognosis, as the posterior cruciate ligament tear heals completely, taking into account some guidelines. The healing process includes several weeks or months and is associated with immobilization of the knee joint. The sooner this is done and the less stress is put on the joint, the shorter the healing path is. The restriction of movement of the knee is essential. In some patients, surgical intervention is necessary. If this proceeds without further complications, the patient can also be discharged from treatment after a few months as symptom-free. In both cases, targeted training and exercise sessions should be taken up following the wearing of a splint for fixation. Their aim is to rebuild the existing musculature as quickly as possible. If medical care is denied, lifelong impairments in locomotion may result.

Prevention

Tearing of the posterior cruciate ligament can only be prevented by avoiding high-risk sports such as American football or field hockey. Strengthening the muscles and regular strength training relieve pressure on the knee joint and can further reduce the risk of a posterior cruciate ligament tear.

Aftercare

Even during conservative treatment or before surgery, the patient should independently begin exercises to tighten the thigh muscle. The attending physician or even the physiotherapist will instruct the patient accordingly here and go through the exercises in detail. However, aftercare for a posterior cruciate ligament injury must be very moderate and gentle compared to other ligament injuries. After the operation, the patient receives a so-called PTS splint. This usually remains on the patient for six weeks. With the PTS splint, a cushion on the lower leg ensures that it is pressed forward. This protects the posterior cruciate ligament replacement. During the first six weeks, exercises are only performed very passively and in the prone position. Here, it is not yet possible to put any weight on the affected leg. Initially, exercises are performed with a maximum weight of ten kilograms. After two weeks, the load weight can be increased to twenty kilograms. Here, too, the exercise period should be about two weeks. After that, loading with half the body weight (under supervision) is possible. Here, too, the load weight should be kept constant for at least two weeks and not increased further. A special posterior cruciate ligament splint is used from the 6th postoperative week. Now, flexion of the leg by approximately 90 degrees is possible and weight-bearing with the full body weight can be performed.

What you can do yourself

Athletes should take a break for at least six months after a posterior cruciate ligament tear. Activities that put a lot of stress on the knee should also be avoided for the first few months after surgery. Cooling and rest are indicated immediately after the procedure. Comprehensive aftercare ensures that the swelling goes down quickly and the pain disappears. Accompanying stretching is important. A motorized splint is used to passively move and stretch the joint. A knee brace is useful for the first six weeks after surgery, because it allows the leg to be stretched without overstretching the affected joint. The thigh muscles must be strengthened in the company of a physiotherapist.Particularly in the first few weeks, it is important to regularly compare the intensity and scope of the exercises and applications with the current condition of the knee. At home, for example, the patient can perform squats or exercises on the ergometer. The physician in charge can best answer which measures are permitted. After the six-month break, sports should be started again very slowly. The affected person can use a special brace to protect the posterior cruciate ligament from further injury.