The anterior cruciate ligament (ACL) is a connective tissue located within the knee joint, connecting the thigh bone (femur) to the shin bone (tibia). It forms an “X” shape with the posterior cruciate ligament. The ACL maintains knee stability by preventing the shin bone from sliding too far forward and limiting excessive rotational movements. It is important for activities involving pivoting, sudden stops, and changes in direction, making it susceptible to injury.
Where ACL Tears Cause Pain
Pain from an ACL tear is felt within the knee, typically in the center or behind the kneecap. The pain is sharp, intense, and immediate, making it difficult to bear weight. Initially, pain can be overwhelming and generalized, but it often concentrates around the front or sides of the knee.
Initial pain may subside, but a persistent dull ache or throbbing sensation often remains. Pain can also occur in the back or sides of the knee, often due to swelling. Nerve compression from swelling can cause pain to radiate down the leg, into the calf, or foot.
Accompanying Symptoms of an ACL Tear
Beyond pain, an ACL tear is accompanied by a “popping” sound or sensation. This sound is a hallmark indicator of the ligament tearing. Rapid swelling of the knee typically occurs within a few hours, resulting from bleeding into the joint (hemarthrosis).
Another symptom is a feeling of instability or the knee “giving way,” especially when pivoting, changing direction, or bearing weight. The knee may feel loose or unable to support the body. Individuals also experience reduced range of motion, finding it challenging to fully straighten or bend the injured leg.
Immediate Steps After Suspecting an ACL Tear
If an ACL tear is suspected, immediate action focuses on managing symptoms and preventing further injury. The RICE protocol (Rest, Ice, Compression, and Elevation) is a first aid measure to reduce pain and swelling. Resting the knee by avoiding weight-bearing, applying ice for 15-20 minutes every few hours, using an elastic bandage for compression, and elevating the leg above heart level provides relief.
Avoid “walking it off” or continuing physical activity, as this can worsen the injury. Seeking professional medical attention from an orthopedic specialist is important for proper diagnosis. A healthcare provider will conduct a physical examination, including tests like the Lachman test, and may order imaging studies such as an MRI to confirm diagnosis and assess damage.