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Anterior Cruciate Ligament (ACL) Injury

The Anterior Cruciate Ligament (ACL) connects the front top of the tibia (the lower leg bone) to the rear bottom of the femur (the thigh bone). Athletes are often diagnosed with this common sports knee injury. 

ACL Injury Causes

An ACL (anterior cruciate ligament) injury can occur due to a variety of causes including:

  • Sports-related activities: Sudden stops, changes in direction, or jumping in sports can stress the ACL.
  • Direct trauma: Knee injuries from car accidents or falls can strain or tear the ACL.
  • Improper landing techniques: Poor form during jumping or landing on a flexed knee or with excessive force can increase ACL injury risk.
  • Overuse and repetitive stress: Continuous strain on the knee joint, especially in activities that stress the ACL, can make individuals more susceptible to ACL tears.
  • Previous injury: Individuals with a history of ACL injury are at increased risk of re-injury.

ACL Injury Risk Factors

Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports, possibly due to pelvic or lower leg alignment. Also, engaging in sports and physical activities that involve cutting, pivoting, jumping, or sudden changes in direction can significantly increase the risk of ACL injuries. Sports such as soccer, basketball, football, skiing, and gymnastics are particularly associated with a higher incidence of ACL tears.

ACL Injury Symptoms

Symptoms of an ACL (anterior cruciate ligament) injury can include:

  • “Popping” noise and feeling of knee “giving out”: Many individuals report hearing or feeling a distinct “popping” sound or sensation at the time of injury. This can occur during a sudden change in direction, landing from a jump, or a direct impact to the knee.
  • Pain with swelling: After an ACL injury, the affected individual may experience pain in the knee. The pain can range from mild to severe, depending on the extent of the injury. Swelling around the knee joint is also a common symptom, often occurring within the first few hours following the injury.
  • Loss of full range of motion: The individual may find it difficult or impossible to fully bend or straighten the knee after an ACL injury. The range of motion is often limited due to the instability caused by the ligament damage.
  • Tenderness along the joint line: The area along the joint line, where the ACL is located, can become tender to touch. Pressing on or palpating this area may elicit pain or discomfort.
  • Difficulty and discomfort while walking: Walking can become challenging and uncomfortable following an ACL injury. The knee may feel unstable, causing the individual to have difficulty bearing weight on the affected leg. This can result in a noticeable limp or an altered gait pattern.

ACL Injury Diagnosis and Treatment

Diagnosis usually involves a physical examination from an orthopedic surgeon, although sometimes imaging tests such as an x-ray or MRI scan help the doctor confirm diagnosis.

Nonsurgical treatment can include bracing or physical therapy, but a torn ACL will not repair itself. Surgical treatment usually involves arthroscopy, where a tiny camera is inserted in the knee through a small incision and connected to a video monitor in the operating room. Your surgeon uses the camera to repair the damaged ACL with tissue from another part of your body, typically a tendon from your knee or hamstring, or from a cadaver. There are risks and benefits to each kind of replacement tissue. ACL reconstruction is usually very successful and rehabilitation includes physical therapy. The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored, typically 4-6 months.