What is ACL Knee Injuries?

Ligaments are tough bands of fibrous tissue that connect two bones. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are inside the knee joint. These ligaments connect the thigh bone (femur) and the large bone of the lower leg (tibia) at the knee joint. The ACL and PCL form an “X” inside the knee that stabilizes the knee against front-to-back or back-to-front forces.

An ACL injury is a sprain, in which the ligament is torn or stretched beyond its normal range. In almost all cases, when the ACL is torn, it’s almost always due to at least one of the following patterns of injury:

• A sudden stop, twist, pivot or change in direction at the knee joint. These knee movements are a routine part of football, basketball, soccer, rugby, gymnastics and skiing. For this reason, athletes who participate in these sports have an especially high risk of ACL tears.
• Extreme hyperextension of the knee. Sometimes, during athletic jumps and landings, the knee straightens out more than it should and extends beyond its normal range of motion, causing an ACL tear. This type of ACL injury often occurs because of a missed dismount in gymnastics or an awkward landing in basketball.
• Direct contact. The ACL may be injured during contact sports, usually during direct impact to the outside of the knee or lower leg. Examples are a sideways football tackle, a misdirected soccer kick that strikes the knee or a sliding tackle in soccer.

Around half of injuries to the ACL include injuries to other parts of the knee as well. The ACL is most often injured by twisting or overextending the knee, especially during sports.

Symptoms of an ACL Knee Injury can Include:

• Feeling a “pop” inside your knee when the ACL tears
• Significant knee swelling and deformity within a few hours after injury
• If you’re playing sport you may not be able to carry on playing.
• You may find that your injured knee loses its full range of movement.
• A black and blue discoloration around the knee, due to bleeding from inside the knee joint
• Your knee may feel unstable, or may not be able to bear your weight.

Causes of ACL Knee Injuries

Most anterior cruciate ligament (ACL) injuries happen during sports, especially football, basketball and skiing. You’re more likely to injure your ACL if you’re a woman. Your ACL injury may be caused by:

• Landing awkwardly from a jump
• Twisting movements, particularly when your foot is on the ground
• Quickly changing direction when running or walking
• Slowing down or stopping suddenly when running

If you’re playing contact sports your ACL may also be injured during direct contact or collision with another player.

How is an ACL Knee Injury Diagnose

Your doctor will check for stability, movement, and tenderness in both the injured and uninjured knee.

You may need imaging tests, such as an MRI. An MRI can show damage to ligaments, tendons , muscles, and knee cartilage.

Types of ACL Knee Injuries

An ACL injury is classified as a grade 1, 2, or 3 sprain.

Grade 1 ACL Knee Sprain

• The fibers of the ligament are stretched, but there is no tear.
• There is a little tenderness and swelling.
• The knee does not feel unstable or give out during activity.

Grade 2 ACL Knee Sprain

• The fibers of the ligament are partially torn.
• There is a little tenderness and moderate swelling.
• The joint may feel unstable or give out during activity.

Grade 3 ACL Knee Sprain

• The fibers of the ligament are completely torn (ruptured); the ligament itself has torn completely into two parts.
• There is tenderness (but not a lot of pain, especially when compared to the seriousness of the injury). There may be a little swelling or a lot of swelling.
• The ligament cannot control knee movements. The knee feels unstable or gives out at certain times.

Treatment for ACL Knee Injuries

Your treatment will depend on the grade of the ACL injury and how much of the ACL is torn, whether other parts of the knee are injured, how active you are, your age, your overall health, and how long ago the injury occurred.

There are 3 Main Treatment for Grade 1, 2 or 3 ACL Knee Sprain:

• KNEE BRACE: Make the knee stable if it is unsteady, or at least make it stable enough to do your daily activities.
• PHYSIOTHERAPY: Make your knee strong enough to do all the activities you used to do.
• AVOID SPORTS: Reduce the chance that your knee will be damaged more.

Treatment for Grade 3 ACL Knee Sprain

Surgery may be used for those needing to return to sports that involve pivoting and jumping. Once swelling subsides, the torn ACL may be reconstructed surgically using either a piece of your own tissue (autograft) or a piece of donor tissue (allograft). When an autograft is done, the surgeon usually replaces your torn ACL with a portion of your own patellar tendon (tendon below the kneecap) or a section of tendon taken from a large leg muscle. Currently, almost all knee reconstructions are done using arthroscopic surgery, which uses smaller incisions and causes less scarring than traditional open surgery.

When To Call Us

Call us immediately if your knee becomes swollen or deformed, even if it is not painful. This is especially important if you cannot bear weight on your injured knee or if the knee feels as if it will buckle or “give out.”

Knee ACL Tear Specialist

Dr Kevin Yip, Arthroscopy Knee Surgeon