What is a ligament?

  • A ligament is a connective tissue (made of mostly collagen) that connects one bone to another
ACL anatomy image.jpg

Where is the Anterior Cruciate Ligament (ACL) and what does it do? And why does it get so much attention?

  • The ACL is one of the main ligaments in the knee joint.  It is located within the knee joint.
  • The ACL is responsible for keeping the stability of the knee joint especially when the person wants to rotate or pivot on the knee.
  • ACL injuries are very common in the sports we love to play.  Some estimates are put to 200,000 ACL tears occur each year in the US.  Any sport that involves pivoting or cutting is a high risk sport (i.e. soccer, football, rugby, skiing, basketball, etc)

**Warning** This video is graphic but shows a compilation of ACL injuries.  Notice how many of these injuries are non-contact and happen during pivoting or landing maneuvers.

Mechanism of Injury

  • The ACL is usually torn as a result of a quick deceleration, hyperextension or rotational injury that usually does not involve contact with another individual.
  • This injury often occurs following a sudden change of direction. A person typically reports feeling a popping sensation in the knee.

Arthroscopic evaluation of an ACL Tear

Symptoms of ACL tear

  • Usually, the patient realizes that something was injured in the knee.  Typically, the patient will feel or hear a "pop"
  • Shortly after the injury, the knee typically becomes fairly swollen and there is some loss of range of motion
  • Over time, the range of motion and swelling improve and the patient may not have many symptoms at all until they pivot or rotate on the knee.  Then they will have buckling, giving way or instability of the knee
ACL tear MRI image.jpg

ACL tear diagnosis

  • The diagnosis can usually be made based on the patient history and physical exam. The are good exam maneuvers that correlate well with ACL tear.  In the acute setting, the exam is more difficult as the patient is usually having more guarding because of the swelling
  • X-rays are usually taken and generally normal with the exception of an occasional bony avulsion fleck sign called a Segond fracture
  • MRI is typically obtained to confirm the ACL tear and to assess whether or not there are any additional injuries to the meniscus or cartilage in the knee
This video is about ACL Reconstruction

ACL Tear Treatment Options

  • Non-surgical:  The ACL tear will not heal itself, but it does not mean that the patient has to have surgery.  Some patients (few) can learn to live without an ACL in their knee.  They usually accomplish this by decreasing their activity level (avoiding pivoting actions), wear a brace, and strengthening their hamstring muscles.
    • There is a dedicated physical therapy program for non-operative management of ACL tears
  • Surgical:  Surgical reconstruction of the ACL tear is generally what the vast majority of patients choose when they tear their ACL.
    • Surgical reconstruction involves replacing the orginal ACL tissue with a tendon graft in the same orientation and attaching the graft to the femur and tibia
    • Surgery is typically outpatient and requires approximately 6 months of healing before getting back into high risk sports.
    • There are many aspects of ACL reconstruction surgery that the patient needs to discuss with their surgeon including but not limited to:  tendon graft choice, post-operative rehabilitation program, post-operative brace usage, general risks of surgery.