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ACL and PCL (Knee Ligament Injury)

The knee is a hinge joint. It joins the thigh and shin bones. There are 2 ligaments inside the knee that protect the joint from too much forward and backward movement. The ACL, or anterior cruciate ligament, keeps the knee from sliding forward. The PCL, or posterior cruciate ligament, keeps the knee from sliding backward.

An ACL or PCL injury occurs when the ligament has been torn. The tear may be partial or complete. Symptoms include knee swelling, pain, and the joint becoming unstable. Some people hear a snap or pop at the time of an ACL injury.

ACL injuries are the most common. They often occur during quick changes in direction while playing sports. An ACL injury may happen at the same time as a cartilage injury of the knee.

The less common PCL injury occurs if the knee bends backwards, or with a direct blow to a bent knee (such as hitting the dashboard with your knee during a car accident).

The pain and swelling of a cruciate ligament injury can last several weeks. It may take 3 to 4 months for the ligament to fully heal.

An ACL or PCL diagnosis can often be made by physical exam. But pain and swelling right after the injury may limit the exam. An MRI may be used to confirm the diagnosis.

Early treatment includes resting the joint, wearing a splint to reduce movement, and using ice to reduce swelling and pain. You may use over-the-counter pain medicine, unless another pain medicine was prescribed. Physical therapy will help you to regain joint and leg strength. Surgery is sometimes needed to treat a more severe cruciate ligament injury.

Home care

  • Stay off the injured leg as much as possible until you can walk on it without pain. If you have a lot of pain with walking, crutches or a walker may be prescribed. These can be rented or purchased at many pharmacies and surgical or orthopedic supply stores. Follow your doctor's advice about when to begin bearing weight on that leg.

  • Keep your leg raised to reduce pain and swelling. When sleeping, place a pillow under the injured leg. When sitting, support the injured leg so it's above heart level. This is very important during the first 48 hours.

  • Apply an ice pack over the injured area for 15 to 20 minutes. Do this every 3 to 6 hours on the first day for pain relief. Keep using ice 3 to 4 times a day until the pain and swelling goes away. To make an ice pack, put ice cubes in a plastic bag that seals at the top. Then wrap the bag in a clean, thin towel or cloth. You can place the ice pack directly over a splint. As the ice melts, be careful that the splint doesn’t get wet. If you have a hook-and-loop knee immobilizer, you can open this to put the ice pack directly to the knee. But always wrap the ice pack in a towel or cloth first. Never put it directly on your skin.

  • If you were given a plaster or fiberglass splint, keep it dry at all times. Bathe with your splint out of the water, protected with a large plastic bag. Seal the top end with a rubber band or tape. If a fiberglass splint gets wet, you can dry it with a hair dryer on a cool setting. If you have a hook-and-loop fastening knee immobilizer, you can remove this to bathe, unless told otherwise.

  • Your provider may prescribe physical therapy. The physical therapist will show you range of motion exercises to practice at home.

  • You may use over-the-counter pain medicine to control pain, unless another medicine was prescribed. If you have chronic liver or kidney disease, or ever had a stomach ulcer, gastrointestinal bleeding, or take a blood thinner, talk with your provider before using these medicines.

  • Learn proper techniques for playing sports or exercising. Training programs can teach athletes how to reduce stress to the ACL. Protective bracing during sports may be helpful to prevent re-injury.

  • Check with your provider before returning to sports or full work duties.

Follow-up care

Follow up with the referral doctor or healthcare provider, or as advised.

If an X-ray, CT scan, or MRI scan was done today, you'll be told of any new findings that may affect your care.

When to get medical advice

Call your healthcare provider right away if any of these occur:

  • Pain or swelling gets worse

  • Swelling, redness, or pain in the calf or thigh

  • The knee gets more unstable, giving out often or locking up

Call 911

Call 911 if you have: 

  • Chest pain 

  • Shortness of breath, with or without chest pain or discomfort

  • Weakness or numbness in the arm, leg, or face (especially if it's only on 1 side)

  • Sudden confusion or trouble speaking

  • Sudden severe headache with no known cause

Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Thomas N Joseph MD
Date Last Reviewed: 2/1/2022
© 2000-2023 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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