Anterior and Posterior Cruciate Ligament Injuries

The anterior and posterior cruciate ligaments are important to the stability of the knee joint. They make the joint stable and yet are configured in such a way as to allow for more than 90 degrees of flexion of the knee.

Anatomy of the Anterior and Posterior Cruciate Ligaments

The knee is one of the more complex joints in the body. It connects the femur to the tibia in the lower leg with the fibula lying along its lateral side. It is connected together with four ligaments. The medial and lateral collateral ligaments prevent side to side motion of the femur across the tibia.

The anterior and posterior cruciate ligaments are complex. The anterior cruciate ligament starts in the anterior aspect of the tibia in the joint space and goes up to the back of the joint space on the femur. It crisscrosses the posterior cruciate ligament that starts in the posterior aspect of the tibial joint space and ends in the anterior aspect of the femur.

The anterior cruciate ligament prevents the tibia sliding forward along the femur, while the posterior cruciate ligament prevents the tibia from sliding backward on the femur.

Anterior and Posterior Cruciate Ligamentous Injuries

Both the anterior and posterior cruciate ligaments can be sprained or torn. They are injured primarily in sports-related injuries but can be injured in falls as well as in motor vehicle accidents.

About half of all damaging injuries to the ACL happen at the same time as damage to the articular cartilage, other ligaments or the menisci of the knee. Injuries to the ligaments in the knee are graded as to their severity:

  • Grade 1 Sprain. This involves a ligament that has become slightly stretched but the knee is technically stable.
  • Grade 2 Sprains. The ligament has become loose or has become partially torn.
  • Grade 3 Sprains. This is when the ligament has completely torn, leaving the joint completely unstable. It is rare to have a partial tear of the ACL. Most injuries of the ACL involve complete tears.

Posterior cruciate ligament tears happen when the knee is in a bent position. This can happen in a sports injury or in situations where a seated person strikes the dashboard with the bent knee.

Posterior cruciate ligament tears involve the exact grades as noted above with ACL ligamentous injuries. One big difference between PCL and ACL tears is that most PCL tears are only partial tears whereas the ACL tears are usually complete.

Symptoms of ACL and PCL Tears

When you get an injury to the anterior cruciate ligaments or the posterior cruciate ligament tears, there are slightly different symptoms:

ACL Tear Symptoms
  • Pain in the knee
  • Swelling, which builds up over twenty-four hours
  • Loss of complete range of motion of the knee
  • Tenderness to palpation of the joint line
  • Pain and inability to walk on the affected leg
  • Unstable knee
PCL Tear Symptoms
  • Pain in the knee
  • Immediate swelling of the knee
  • Difficulty or impossibility of walking on the affected leg
  • The knee feels like it is going to “give out”
Causes of ACL and PCL Injuries

The causes of an ACL tear and a PCL tear are slightly different. For example:

ACL Tear Causes
  • Automobile accident
  • Changing direction quickly, as in football or soccer
  • Stopping running quickly or suddenly
  • Running and slowing down rapidly
  • Landing a jump the wrong way
  • A football tackle with a direct collision

According to research, women have a higher risk of ACL injury than male athletes, depending on the sport. It is felt to be due to differences in muscular strength, neuromuscular control and physical conditioning. Some people feel the difference is due to changes in the shape of the pelvis and in the lower extremity alignment that makes females have loose ACLs in the first place. Estrogen also has an effect on the properties of the ligaments.

PCL Tear Causes

It usually takes a great amount of force to injure the posterior cruciate ligament in the following ways.

  • A direct blow to the bent knee in an automobile injury
  • A sports injury in which the knee is bent
  • Pulling on the ligament in a twisting injury or hyperextension
  • A misstep on uneven terrain
Diagnosis of Cruciate Ligament Injuries

The doctor will evaluate your injury by checking for knee instability, while comparing the findings to the uninjured knee. In PCL injuries, the knee will sag backwards when bent. In addition, it can slide further back when the knee is bent at greater than a 90 degree angle. X-rays cannot show the actual ligament but can reveal if the ligament has torn off a piece of the bone at the time of the injury. Such an event is called having an “avulsion fracture” of bone.

An MRI is the best way to assess ligamentous injury in the knee joint. It uses radio waves and a strong magnet to visualize bones and soft tissue. If the injury is at least 3 months old, however, it may not show up on MRI scanning.

Treatment of Cruciate Ligament Injuries

The best treatment for an anterior cruciate ligament tear depends on the person’s needs. Athletes usually want to get back into sports. Older people may just want to be able to return to normal activities without problems. The treatment of ACL injuries can be nonsurgical or surgical.

A torn anterior cruciate ligament does not heal without having surgery to it. Even so, people with a low activity level or people who are elderly can tolerate having their ACL torn if they don’t want to be very active and the joint is basically stable. The doctor might recommend a knee brace to enhance stability of the knee. Crutches or a walker can be used to limit the amount of weight bearing on the affected leg.

If the swelling goes down, a program of careful rehab is recommended with exercises that strengthen the muscles around the knee. Physical therapy can take a few weeks up to a few months.

Surgical treatment is the definitive way to heal an ACL joint. In general, the ACL joint can’t simply be stitched together. Usually, the surgeon will use a tissue graft on the ligament that acts like a scaffold for the new ligament to grow back onto. Grafts can be taken from the patellar tendon, from the hamstring tendon or from donor tissue.

Even with this kind of repair, it can be many months before the tendon is strong enough to be able to use it fully.

The procedure is usually done arthroscopically. It is less invasive than normal surgery and the individual heals faster from the procedure. It is usually delayed to allow the inflammation of the tendon to heal. If you repair the ACL ligament too early, there is an increase in scar formation of the joint. This can limit knee mobility over the long haul.

When treating the posterior cruciate ligament, it is fortunate that many injuries heal without surgery. Rest, ice, compression and elevation can be good enough when it comes to treating the PCL. The doctor may then recommend a knee immobilizer to prevent knee movement. Crutches or a walker can be used to prevent putting too much weight on the knee.

Surgical treatment is recommended if there are multiple injuries inside the knee. Usually the knee is very unstable at that point and needs many aspects treated surgically. As with the ACL injury, a tissue graft must be used to rebuild the ligament with scaffolding. The graft can be taken from another body area or from a cadaver.

The procedure is done using an arthroscope with small incisions in the skin. As time has gone on, better and better procedures are being developed to repair the posterior cruciate ligament.

Rehabilitation of Cruciate Ligament Repairs

Rehabilitation is used for both ACL and PCL tears and is used both with and without surgical intervention. Physical therapy is designed to increase the mobility and strength of the knee. It is usually started from 1 to 4 weeks after surgery. Physical therapy can last several months and it can take 6-12 months for full recovery. The final aspect of rehabilitation is aimed at the athlete’s functional return to sports.

Complications of Cruciate Ligament Repairs

The complications of cruciate ligament tears are about the same if it is an ACL tear or a PCL tear. These complications include:

  • Neurovascular injury
  • Osteonecrosis
  • Laxity that doesn’t go away
  • Loss of motion of the knee
  • Long standing knee pain

If you or a loved one has suffered a ligament injury as a result of someone else's negligence and would like to discuss your legal options with an experienced Sacramento Personal Injury Attorney, contact us online or call us at 916-921-6400 or toll-free at 800-404-5400 to set up a FREE consultation.

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