Diagnosing Anterior Cruciate Ligament Tears

NYU Langone sports medicine doctors specialize in diagnosing and treating anterior cruciate ligament (ACL) tears, a type of knee injury.

A ligament is a fibrous band of tissue that connects a bone to another bone. Two cruciate ligaments, critical for knee stability, reside inside the knee and attach to the bottom of the femur, or thigh bone, and the top of the tibia, or shinbone. The cruciate ligaments cross each other, forming an X, with the ACL in front and the posterior cruciate ligament in back. The ACL keeps the tibia from sliding out in front of the femur and helps support the knee while rotating.

ACL injury can result in frequent episodes of your knee giving way, which may limit activity and lead to further knee damage.

A complete ACL tear means the ligament has severed into two pieces. Sometimes, the ACL partially tears, meaning that not all the fibers of the ligament have been disrupted.

Symptoms of ACL Tears

An ACL can tear when you suddenly pivot on your feet or slow down and change direction rapidly when playing sports such as basketball or soccer. An injury can also occur when you suddenly stop during running or if you land awkwardly when jumping. A direct blow to the knee from contact sports such as football can also result in a tear.

An ACL injury typically causes acute pain. You may also hear a popping noise as the ligament tears. After the injury, the pain subsides, but you may experience swelling and instability or buckling of the knee, especially when pivoting. You may also have reduced range of motion in the knee joint and experience discomfort when walking.

Diagnostic Tests for ACL Tears

Your doctor may perform a physical exam and imaging tests to diagnose an ACL tear.

Physical Exam

During a physical exam, your doctor checks the knee for swelling, tenderness, range of motion, stability, and ACL function. You may also discuss your symptoms, your physical activities, and how you sustained your injury.

Imaging Tests

Your doctor may order an X-ray to rule out any broken bones in the knee joint that could be contributing to your symptoms. Additionally, an MRI enables your doctor to see detailed images of the soft tissues, including ligaments, tendons, and cartilage. An MRI can show whether you have an ACL tear, depict the severity of the injury, and diagnose other injuries such as a meniscus tear or knee cartilage injury.