What is an ACL injury?

An anterior cruciate ligament (ACL) injury is one of the most common knee injuries. An ACL injury is a tear in the ACL ligament — one of the four ligaments in the knee that keeps the joint stable and connects the thighbone to the tibia. The ACL is located in the middle of the knee.

ACL injuries can range from mild to severe. A mild ACL injury is a small tear in the ligament. A severe ACL injury occurs when the ligament tears completely or when part of the bone separates from the ligament.

Common related conditions
Knee Strain or Sprain Lateral Collateral Ligament (LCL) Injury Medial Collateral Ligament (MCL) Injury Posterior Cruciate Ligament (PCL) Injury

Causes of anterior cruciate ligament (ACL) injury

ACL injuries are very common in sports like downhill skiing, football, basketball and soccer. Typically, an ACL injury occurs when a sudden force hits the knee while the foot is planted on the ground and your leg is straight or slightly bent.

Other causes of an ACL injury include:

  • Falling off a ladder
  • High-impact contact by another person
  • Changing direction rapidly while running or walking

Risk factors for anterior cruciate ligament (ACL) injury

  • Age — people over the age of 40 are at a higher risk of suffering from an ACL injury because the ACL weakens with age.
  • Previously torn ACL — if you have suffered an ACL injury in the past, you are more likely to suffer from one in the future.
  • Sports that require cutting, pivoting and single-leg landings — people who participate in sports like basketball, soccer, football, volleyball, tennis, downhill skiing are at higher risk for tearing an ACL.
  • Gender — women are four to six times more likely to suffer ACL tears.

Symptoms of anterior cruciate ligament (ACL) injury

The most common symptoms of an ACL injury are pain and swelling on the outside and back of the knee joint within a few hours of the injury. Although the pain may stop the person from continuing to do the activity that caused the injury, the patient may be able to walk.

Other symptoms of an ACL injury:

  • Popping sensation in the knee when injured
  • Inability to move the knee
  • Instability in the knee

Diagnosis of anterior cruciate ligament (ACL) injury

An ACL injury is diagnosed in a physical exam with your orthopedic physician.

Your doctor will ask questions to determine how the knee was injured as well as to understand the history of the injured knee. They will examine your knee for signs of swelling and tenderness. He or she may move the knee to assess overall function and range of motion in the knee.

Your provider may order diagnostic images such as an x-ray or MRI to determine if the knee bones, ligaments, tendons or knee cartilage have been damaged. He or she may also perform a knee arthroscopy, making an incision in the knee and inserting a tool to look inside the knee.

Treatments for anterior cruciate ligament (ACL) injuries

If you suspect you have an ACL injury, it is important to rest, ice, compress and elevate the affected area as soon as possible. You can also take an anti-inflammatory medication to relieve the pain and reduce swelling. You should schedule an appointment as quickly as possible to determine the severity of your injury and begin treatment.

The treatment protocol for ACL injuries will depend on the severity of the injury, your age and health and whether other areas of the knee are also injured.

  • Surgical reconstruction — your orthopedic surgeon will evaluate whether ACL surgery is appropriate for your case.
  • Platelet rich plasma (PRP) injection — platelet rich plasma is used to help speed recovery of muscles and ligaments. In a PRP procedure, blood is drawn from the patient and spun in a centrifuge to concentrate the platelets, then are injected into the affected area.

Recovery from anterior cruciate ligament (ACL) injury

The recovery period after ACL surgery is long and grueling, requiring months of physical therapy. If you have surgery to correct an ACL injury, your provider will prescribe physical therapy to rebuild and strengthen the knee.

It is important to follow the physical therapist’s instructions in order to strengthen the knee enough to return to your previous level of activity and avoid future injury.

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