The posterior cruciate ligament (ligament) runs diagonally from the thigh bone (called femur) to the larger bone of the lower leg (called the tibia).
Together with the anterior cruciate ligament (ACL), they form an “X” in the middle of the knee joint and provide great stability against forward-backward and backward-forward movements of the knee.
The PCL is responsible for preventing the shin bone from moving too far back in relation to the thigh bone. It is two times stronger and thicker than the ACL. It is considered the strongest ligament of the knee joint; thus, it is not commonly injured.
PCL injuries are not as frequent as other ligament injuries of the knee. Although it is a strong ligament, excessive force or pressure may cause it to stretch or tear. Injuries to the ligaments are called a sprain, which is graded based on their severity.
- Mild or Grade I: There is limited damage or micro-tears to the PCL due to overstretching. It can still stabilize the knee and may not cause any dysfunction to the individual.
- Moderate or Grade II: There is a partial tear on the PCL. It becomes loose and unable to stabilize the knee. Also, the knee may sometimes give out in standing or walking.
- Severe of Grade III: There is a complete tear of the PCL in one of its bony attachments. The knee becomes highly unstable and unable to support the body. Because it is a strong ligament, severe PCL injuries are often associated with other knee ligament injuries.
PCL Tear Symptoms
A mild PCL sprain may not be painful or cause any problems with moving the knee. Some are still able to function and perform activities. Further, some with minor injuries do not even seek medical advice until another knee injury occurs. Some symptoms that can be felt are as follows:
- Minimal pain at the back of the knee, especially when kneeling or crouching, and pain in front of the knee when running especially when slowing down.
- Mild swelling
- The knee feels wobbly or is giving out. Some patients may report that the knee feels unusual and is “not the same as before.”
For severe PCL injuries that involve other ligaments, one may feel unstable, may have difficulty moving the knee, limited range of motion, and may be unable to put weight on the injured leg.
Causes of PCL Injury
The most common cause of PCL injury is a direct and forceful blow in front of the lower leg when the knee is bent. This usually occurs
- During automobile accidents that result in dashboard injuries
- Falling on a bent knee during a sports activity. PCL injuries are common in sports such as football, soccer, baseball, and skiing.
A detailed physical examination and history taking are essential to understand the symptoms and the mechanism of how the injury occurred. This will enable the medical practitioner to determine the severity of the PCL injury and if other soft tissues of the knee are damaged.
The doctor will ask about how the injury occurred and if the patient was involved in a car accident or sports-related activity.
- Both knees will be examined and compared in terms of swelling, tenderness, deformity, and excessive fluid inside the knee joint.
- Knee range of motion will also be checked.
- The doctor may press against the shin in a lying-down position to check abnormal movements or pull the shin bone to determine the strength of the ligaments.
- The injured knee may seem to sag backward, and the shin bone may move back too much, especially when the knee is bent beyond 90 degrees.
- The greater the backward movement of the shin bone, the more severe the PCL injury is and the greater the instability of the knee.
- The doctor may also check the strength of the leg muscles, gait pattern, and ability to put weight on the injured leg.
- An X-ray may be ordered to check for any bone fractures. Since the PCL is a strong ligament, it may pull off a piece of its bony attachment during injury; this is called an avulsion fracture.
- Magnetic resonance imaging (MRI) may also be required to visualize better the PCL and other soft tissues of the knee.
- A bone scan may be ordered for chronic injuries, which are minor injuries that repeatedly occur over time. This is usually necessary for patients that experience persistent pain, swelling, and knee instability to detect any changes that may suggest arthritis and/or knee cartilage degeneration.
Minor PCL injuries that cause mild pain and swelling and do not result in knee instability are usually not detected or reported. Adequate rest and over-the-counter medications are usually sufficient to manage the symptoms and return to normal activities.
Normally, mild or grade I and moderate or grade II PCL injuries usually heal fast, allowing the patient to return to normal activities within 2 to 4 weeks.
For grade I or grade II injuries that result in knee instability, problems with moving, and difficulty in putting weight on the injured leg, the following are recommended:
- Immobilization of the injured knee in extension or straight leg position for 2 to 3 weeks.
- Partial or full weight-bearing depending on the severity and tolerance of the patient.
- Physical therapy intervention that includes strengthening the leg muscles, especially thigh muscles (the quadriceps), to support the knee and prevent re-injury.
For severe or grade III PCL injuries, conservative management may also be done, which include immobilization in full extension for up to 4 weeks to allow the structures of the knee to completely heal, non-weight bearing or partial weight-bearing exercises usually done in the pool, and physical therapy intervention for muscle strengthening and general body conditioning.
For athletes who sustained grade III PCL injuries, return to play may usually be done within 3 to 4 months.
Aside from conservative treatment, surgical intervention may be done for those with grade III injuries and those who sustained an avulsion fracture.
- A PCL pulled from one of its bony attachments may be reattached using a screw.
- If it is torn completely, a graft may be used from one of the large muscles of the thigh to reconstruct the PCL.
Complete healing and recovery after surgery may take between 6 to 12 months, depending on how severe the injury is.
Home Remedies/ Management
Mild or grade I PCL injuries may not require any intervention at all. The following may be done at home to manage the pain and swelling:
- Resting the injured leg and avoiding weight-bearing.
- Ice pack application [for 15-20 minutes] every 2 -3 hrs for first 2 days followed by placing warm compress after 2 days.
- Using compression bandage.
- Elevating the injured leg.
- Taking non-steroidal anti-inflammatory drugs (NSAID) for minor pain and swelling.
Sports-related injuries such as PCL injuries and other knee injuries can be prevented through the following:
- Performing warm-up exercises before engaging in sports-related or recreational activities.
- Strengthening the muscles that support the knee.
- Gradually increasing the intensity of exercises to avoid undue stress.
- Removing unnecessary obstacles in the playing field may cause unwanted twisting of the knee or result in tripping while running.
- De Carlo, M. Clinics in Sports Medicine, January 2010.
- American Academy of Orthopaedic Surgeons: “Posterior Cruciate Ligament Injuries.”
- Frontera: Essentials of Physical Medicine and Rehabilitation, 2nd edition.
- DeLee and Drez’s Orthopaedic Sports Medicine, 3rd edition.
- Canale & Beaty: Campbell’s Operative Orthopaedics, 11th edition.
- Posterior cruciate ligament injuries. (2009, February).
Dr Aarti is an MBBS (Bachelor of Medicine and Surgery) from Baroda Medical College (The Maharaja Sayajirao University, Baroda). Dr. Aarti has also completed her Masters of Medical Science and Technology from the prestigious Indian Institute of Technology, Kharagpur.