ACL injuries are among the most common knee injuries seen in active adults, athletes and even teens. While these injuries can be serious, treatment isn’t the same for everyone, and with an individualized approach, many people can return to the activities they enjoy safely and successfully.
What Is the ACL (Anterior Cruciate Ligament)?
The anterior cruciate ligament (ACL) is one of the four major ligaments in the knee. Its main job is to stabilize the knee, especially during movements that involve:
- Sudden stops
- Pivoting or twisting
- Changing direction quickly
- Jumping and landing
Where is your ACL located? The ACL runs diagonally through the center of the knee, connecting the femur (thigh bone) to the tibia (shin bone). It helps prevent the tibia from sliding too far forward and controls the rotational stability of the knee.
What Causes ACL Injuries?
An ACL tear is one of the most common sports injuries in adults and adolescents. In most cases, it happens without direct contact, meaning you don’t have to be tackled or hit to experience a serious injury.
Common causes of ACL tears and injuries include:
- Sudden pivoting or cutting movements
- Landing awkwardly from a jump
- Rapid deceleration or stopping
- Twisting the knee while the foot is planted
Sports—especially soccer, basketball, football, skiing and lacrosse—put both adolescents and adults at greater risk of ACL tears because they involve sudden stops, quick changes in direction, jumping and awkward landings that place high stress on the knees.
That said, non-athletes can also tear their ACL, such as through falls, accidents or sudden missteps.
What Does a Torn ACL Feel Like?
Symptoms of a torn ACL vary but often include:
- A popping sensation at the time of injury
- Immediate knee swelling (within hours)
- Pain and difficulty bearing weight
- A feeling that the knee is unstable or “giving out”
- Trouble walking normally
- Reduced range of motion
When the ACL is torn, it can be either partial or complete. A partial tear means some fibers remain intact and the knee might feel mildly unstable, while a complete tear involves a full rupture that often causes significant instability.
How Is an ACL Tear Diagnosed?
A diagnosis of a torn ACL usually involves a physical exam to test knee stability, along with imaging (typically an MRI) to confirm the tear and check for other injuries (such as meniscus or cartilage damage).
Advancing imaging will determine if the tear is partial or complete, which will guide treatment decisions.
When Is ACL Surgery Recommended?
ACL reconstruction involves replacing the torn ligament with a graft (a piece of healthy tissue), usually taken from the patient’s own body, such as the hamstring or patellar tendon, or from a donor. The new ligament acts as a scaffold while the body heals and restores stability.
ACL reconstruction surgery is often recommended for:
- Athletes who want to return to cutting or pivoting sports
- Patients with persistent knee instability
- Individuals with combined injuries (ACL plus meniscus or cartilage damage)
When to See an Orthopedic Specialist
If you’ve experienced an ACL injury, getting a diagnosis right away and beginning treatment can help protect the knee from further damage and improve long-term outcomes.
Seek medical evaluation by a sports medicine orthopedic specialist as soon as you can if you experience symptoms such as:
- Knee swelling after an injury
- Instability when walking
- Difficulty returning to normal activities
- Pain or limited motion that doesn’t improve
Frequently Asked Questions About ACL Injuries
Can you still walk with a torn ACL?
Yes, some people can still walk with a torn ACL after the initial pain and swelling decrease. However, walking doesn’t mean the knee is stable. Many patients who can walk while injured continue to experience instability during activities that involve turning, pivoting or sudden movements.
Can a Torn ACL Heal Without Surgery?
The ACL does not heal on its own the way muscles or some other ligaments can. Whether or not surgery is necessary depends on factors like your activity level, your age, if your knee feels unstable and if you have other injuries (such as meniscus tears).
Some people, such as those who are less active or who don’t participate in sports that involve pivoting, cutting, or jumping, might be able to manage a torn ACL without surgery. In those cases, physical therapy and modifying their activities can do enough to help them recover and meet their goals.
How Long Does an ACL Tear Take to Heal?
Without surgery, improvement can take several months when physical therapy (PT) is done consistently. Even with PT, some degree of instability can remain.
With ACL surgery, full recovery typically takes 9 to 12 months. The exact length depends on the person’s overall strength and commitment to rehabilitation. Returning to high-impact or competitive sports too early and before a full recovery increases the risk of re-injury.
What Is the Role of Physical Therapy in ACL Recovery?
Physical therapy is a critical part of recovery for most people with ACL injuries, whether with or without surgery. A structured PT program helps:
- Reduce swelling and restore range of motion
- Strengthen the quadriceps, hamstrings and core
- Normalize gait, improve balance, coordination and knee stability
- Safely progress back to daily activities and sports-specific movements
Can ACL Injuries Be Prevented?
Not all ACL injuries can be prevented, but the risk can be significantly reduced. Prevention strategies include:
- Strengthening the legs and core muscles with targeted exercises
- Learning proper landing, cutting and pivoting mechanics
- Participating in balance and neuromuscular training programs
- Using sport-specific injury prevention programs, especially for young and adolescent athletes, which have been shown to lower ACL injury risk in sports with frequent jumping and direction changes
At Stony Brook Orthopaedic Associates, our specialists have extensive experience diagnosing and treating ACL injuries, including both non-surgical management and advanced ACL reconstruction and rehabilitation. We work closely with physical therapists, sports medicine providers and athletic trainers to create personalized treatment plans that support safe recovery and return to activity. To learn more or schedule an evaluation, visit Stony Brook Medicine’s Division of Sports Medicine or speak with your primary care provider for a referral.
