One of the most common knee injuries is an anterior cruciate ligament (ACL) sprain or tear. The ACL is one of the key ligaments that help stabilize your knee joint. It is the tissue that connects the thigh bone to the shinbone.

The ACL can be injured in several ways:

• Stopping or changing direction rapidly
• An improper landing from a jump
• Trauma like direct contact from sports or some other type of collision

Sports involving sudden stops and changing directions are the most common culprits for ACL injuries. This includes sports like basketball, soccer, tennis, football, skiing, and volleyball.

Studies have identified female athletes as more likely to incur an ACL injury than male athletes in certain sports. About half of the ACL injuries are accompanied by damage to other structures in the knee, such as articular cartilage, meniscus, or other ligaments.

Partial ACL tears are rare. Most ACL injuries are complete or near-complete tears.
Injured ligaments are considered "sprains" and are graded on a severity scale from Grade 1 to Grade 3.

Treatment may include surgery and physical therapy.

Signs and Symptoms

• Knee swelling
• Instability or loss of full range of motion
• Tenderness and discomfort while walking
• A "popping" sensation in the knee
• Severe pain and inability to continue activity