Knee Ligament Injuries

The knee is the largest joint in the body and is vital to movement. The stability of the knee mostly depends on the ligaments and muscles around it. Therefore, injuries to knee ligaments are common. In 2003, more than 9.5 million people visited orthopaedic surgeons because of knee problems.

Two sets of ligaments in the knee give it stability: the cruciate ligaments and the collateral ligaments.

Cruciate Ligaments

The cruciate ligaments are located within the knee joint and connect the thighbone (femur) to the shinbone (tibia). They function like short ropes that hold the bones of the knee joint tightly together when the leg is bent or straight. This is needed for proper knee joint movement.

The cruciate ligaments are so named because they cross each other to form an “X.” The term cruciate comes from the Latin word crux, which means “cross.”

The cruciate ligament located toward the front of the knee is the anterior cruciate ligament (ACL). The cruciate ligament located toward the rear of the knee is the posterior cruciate ligament (PCL).

 

ACL Injuries

Causes

The ACL prevents the shinbone from sliding forward beneath the thighbone.

The ACL can be injured in several ways:

  • Changing direction rapidly
  • Stopping suddenly
  • Slowing down while running
  • Landing from a jump
  • Direct contact or collision, such as in a football tackle

Symptoms

If you injure your ACL, you may not feel any pain immediately. However, you might hear a popping noise, and you may feel your knee give out from under you.

Within 2 to 12 hours, the knee will swell, and you will feel pain when you try to stand. Apply ice to control the swelling, and elevate your knee until you can see an orthopaedic surgeon.

If you walk or run on an injured ACL, you can damage the cushioning cartilage in your knee. For example, if you plant your foot and then turn your body to pivot, your shinbone may stay in place as your thighbone above it moves with the rest of your body.

Diagnosis

Diagnosis of an ACL injury is based on a thorough patient history and physical examination of the knee. The examination may include several tests to see if the knee stays in the proper position when pressure is applied from different directions.

Your orthopaedist may order an X-ray and a magnetic resonance imaging (MRI) scan of the knee. In some patients, arthroscopic inspection of the knee joint is required.

Treatment

A partial tear of the ACL may or may not require surgical treatment. A complete tear is a more serious injury. Complete tears, especially in younger athletes, may require reconstruction. Both nonsurgical and surgical treatment options are available for ACL injury.

Nonsurgical Treatment

Nonsurgical treatment may be used because of a patient’s age (very young or elderly) or overall low activity level. It may be recommended if the overall stability of the knee is intact. Nonsurgical treatment involves a program of muscle strengthening, often with the use of a brace to provide stability. Activities should be modified to limit cutting or pivoting movements.

Surgical Treatment

Arthroscopic surgery or open surgery may be performed. Surgery involves reconstruction of the damaged ligament using a strip of tendon from the patient’s knee (patellar tendon) or hamstring muscle. Surgery is followed by an exercise and rehabilitation program to strengthen the muscles and restore full joint mobility.

 

PCL Injuries

Causes

The PCL functions to prevent the shinbone from sagging backwards. When the PCL is torn, the bones of the knee can rub directly against each other, causing wear and tear to the thin, smooth cartilage. This may lead to arthritis in the knee.

The PCL is not injured as frequently as the ACL. The PCL can be injured in several ways:

  • Pulling or stretching of the ligament (PCL sprain)
  • Blow to the front of the knee
  • Simple misstep

Symptoms

Patients with PCL injuries often do not always have symptoms of knee instability.

Diagnosis

Diagnosis of a PCL injury is based on a thorough physical examination of the knee. The examination may include several tests to see if the knee stays in the proper position when pressure is applied from different directions.

Your orthopaedist may order an X-ray and a magnetic resonance imaging (MRI) scan. In some patients, arthroscopic inspection is required.

Treatment

Because patients with PCL injury often do not have symptoms of knee instability, surgery is not always needed. Many athletes return to activity without significant impairment after completing a prescribed rehabilitation program. This is especially true for partial PCL tears.

However, if the PCL injury pulls a piece of bone out of the top of the shinbone, surgery is needed to reattach the ligament. Knee function after this surgery is often quite good.

Collateral Ligaments

The collateral ligaments are located on the inner (medial) side of the knee joint and the outer (lateral) side of the knee joint. The medial collateral ligament (MCL) connects the thighbone to the shinbone, and provides stability to the inner side of the knee. The lateral collateral ligament (LCL) connects the thighbone to the other bone in the lower portion of the leg (fibula) and stabilizes the outer side.

Collateral Ligament Injuries

Injuries to the MCL are usually caused by contact on the outside of the knee and are accompanied by sharp pain on the inside of the knee. The LCL is rarely injured.

Treatment

If the MCL has a small partial tear, conservative treatment usually works. Remember the acronym RICE:

  • Rest the knee to give the ligament time to heal.
  • Ice can be applied two or three times a day for 15 to 20 minutes each time.
  • Compress the injury to limit swelling. You may have to wear a bandage or brace for a while.
  • Elevate the knee whenever possible.

You should also consult your physician about a course of rehabilitation exercises for good healing.

If the collateral ligament is completely torn, or torn in such a way that the ligament cannot heal, you may need surgery. Repair may bring good results, with a return to good knee stability. After satisfactory rehabilitation, many people resume their previous levels of activity.

Rehabilitation

A rehabilitation plan is needed if you have a cruciate or collateral ligament injury.

Most rehabilitation plans include:

  • Passive range-of-motion exercises designed to restore flexibility
  • Braces to control joint movement.
  • Exercises to strengthen the quadriceps muscles in the front of the thigh. Muscle strength is needed to provide the knee joint with as much support and stability as possible when weight is placed on it.
  • Additional exercises on a high-seat exercise bicycle, followed by more strenuous quadriceps exercise.

Your progress and the ability of the knee to function as a normal knee will determine how long you must use crutches and a brace.

Chinese Translation

Chinese Translation (http://hkoa.org/translated/knee%20ligament%20injury.html)

AAOS wishes to thank The Hong Kong Orthopaedic Association for translating this information into Chinese and for their support of educational programs for patients and the public.