ACL tears

The anterior cruciate ligament, or ACL, is a strong band of tissue deep inside the knee. It connects the thigh bone to the shin bone and is one of the main structures that keeps the knee stable — especially during pivoting, cutting, and landing.

Because the ACL helps control side-to-side and rotational stability, it matters most in activities that involve quick changes of direction, which is why ACL injuries are common in sports like soccer, basketball, and skiing.

An ACL tear means the ligament has been stretched beyond what it can handle and its fibers have been damaged. Most ACL tears are complete tears, meaning the ligament is torn through. Partial tears, in which some ligament fibers remain intact, are less common.

When the ACL is torn, the knee can lose some of its normal stability. How much that affects a given person depends on the injury, the other structures in the knee, and what that person needs to do day to day.

Many ACL injuries occur during a sudden pivot, an awkward landing, or a rapid change of direction — sometimes without anyone else being involved. They can also happen from a direct blow to the knee.

• A “pop” at the time of injury, felt or heard by some people
• Swelling in the knee, often within the first several hours
• Pain, especially with weight-bearing or twisting
• A sense that the knee is loose, unstable, or “giving way”
• Trouble returning to sport or activity because the knee doesn't feel dependable

Evaluation begins with a discussion of how the injury occurred and a physical examination.

X-rays are used to evaluate for fractures and, in younger patients, to assess the growth plates. An MRI is typically obtained afterward to confirm the ACL injury and identify associated damage to structures such as the meniscus or cartilage.

Not every ACL tear is treated the same way. Reconstruction may be considered when instability interferes with desired activities or when associated injuries affect the treatment decision. Patients who want to return to athletic activities typically require reconstruction, particularly when those activities involve pivoting, cutting, or rapid changes of direction.

The right path is individual. It's a decision you make together with your surgeon after understanding your specific injury, your goals, and the trade-offs of each approach.

Several things are usually part of the conversation when deciding how to treat an ACL tear. None of these is a rule on its own; they're weighed together for your situation.

• What you want to get back to — the activities, sports, work, and daily demands that matter to you
• How stable the knee feels and whether it gives way during normal activity
• Whether other structures, such as the meniscus or cartilage, were also injured
• Your overall health, age, and preferences
• How the knee responds to an initial period of rehabilitation

Nonsurgical care centers on rehabilitation — a guided program that restores range of motion, strength, and neuromuscular control, and helps you judge how the knee performs with activity. For some people this is enough to meet their goals.

Surgical care most often means ACL reconstruction, in which the torn ligament is rebuilt using a graft, followed by a structured rehabilitation program. The treatment page explains reconstruction in more detail, including how graft choices and recovery are approached.