An anterior cruciate ligament (ACL) tear is a common knee injury to the ligament that steadies the joint and stops the shin bone sliding forward. This guide explains the symptoms and causes of an ACL tear, how it is diagnosed and what treatment options exist.
Note: If you felt a pop in the knee at the time of injury followed by fast swelling or being unable to bear weight, see an orthopedic surgeon. Diagnosis needs an in-person examination.
Symptoms of an ACL tear
Symptoms of a tear may include the following, and they can resemble other knee injuries:
- A pop heard or felt at the time of injury
- Fast swelling of the knee within hours
- Severe pain that stops you playing on
- A feeling that the knee is unstable or gives way
- Difficulty straightening or bending the knee
- Difficulty putting weight on the leg
How does an ACL tear happen?
The injury usually happens during a sudden movement, most often from:
- Changing direction quickly while running
- Landing badly after a jump
- Stopping suddenly
- Twisting the knee with the foot planted
- A direct blow in contact sports
- Falls or road accidents
How is an ACL tear diagnosed?
Diagnosis starts with how the injury happened, followed by an examination in which the doctor tests the knee's stability by hand. An X-ray rules out fractures, and an MRI is usually requested to confirm the tear and show related injuries such as a meniscus tear. A tear cannot be confirmed without an in-person examination.
Treatment options
Non-surgical treatment
Not every patient needs surgery. The decision depends on age, activity level, sport, how stable the knee is and any other injuries in the joint.
- Rest and activity changes at first
- Cold packs wrapped in cloth and elevation to ease swelling
- Physiotherapy to restore movement and strengthen the muscles
- A knee brace when needed
- Avoiding twisting and pivoting sports if the knee stays unstable
Surgical treatment
If the knee stays unstable, or the patient is an athlete who needs a stable joint, the surgeon may recommend arthroscopic ACL reconstruction. Related injuries are often treated during the same operation.
Recovery and rehabilitation
Rehabilitation is essential whether treatment is non-surgical or surgical. Recovery time varies from person to person and is set by the surgeon after assessment. See knee rehabilitation and returning to sport.
- Controlling pain and swelling
- Restoring knee range of motion
- Strengthening the thigh and leg muscles
- Balance and movement-control exercises
- A gradual return to activity
When to see the doctor
See an orthopedic surgeon promptly if:
- You heard or felt a pop at the time of injury
- The knee swelled quickly
- You cannot stand or bear weight
- The knee feels unstable or gives way
- The knee locks and will not straighten
- You notice numbness or a change in the colour of the foot