A torn anterior cruciate ligament, commonly known as the ACL, is one of the most common knee injuries among athletes and active adults. The injury can sideline athletes for months and often raises questions about whether surgery is necessary, how long recovery takes and when it is safe to return to sports.

"An ACL injury can be a significant setback, but with the right treatment plan, most patients are able to return to the activities they enjoy," said Jason Dragoo, MD, an orthopedic sports medicine surgeon at CU Medicine Orthopedic and Sports Medicine – Steadman Hawkins Clinic Denver.

What is the ACL?

The ACL is one of the major ligaments in the knee. It connects the femur (thigh bone) to the tibia (shin bone) and helps stabilize the joint during movement.

The ligament is particularly important during activities that involve pivoting, cutting, sudden stops or changes in direction.

When the ACL tears, the knee can become unstable, making it difficult for patients to participate in sports or other physical activities.

How Do ACL Injuries Occur?

ACL tears often occur without direct contact. “In Colorado, we see a lot of ACL tears from activities ranging from skiing, snowboarding, flag football and beyond,” said Dr. Dragoo.

Common causes include:

• Landing awkwardly after a jump
• Suddenly changing direction
• Pivoting with a planted foot
• Skiing accidents
• Sports-related collisions

What are the Symptoms of an ACL Tear?

Symptoms can vary, but common signs include:

• A popping sensation in the knee
• Rapid swelling
• Pain with activity
• Reduced range of motion
• A feeling that the knee may buckle or give way
• Inability to return to the activity on the day of injury

Patients experiencing these symptoms should seek evaluation from a sports medicine specialist. Other structures in the knee, including the meniscus or cartilage, can also be damaged during an ACL injury.

“Many patients report hearing or feeling a pop at the time of injury. Swelling typically develops within hours and may be accompanied by pain and a feeling that the knee is unstable,” said Dr. Dragoo.

Do ACL Tears Require Surgery?

Not all ACL tears require surgery and Dr. Dragoo’s team does a thorough evaluation to ensure the injury actually requires treatment other than physical therapy.

Treatment recommendations depend on several factors, including a patient's age, activity level, goals and degree of knee instability.

Patients who participate in sports that require pivoting and cutting movements, such as soccer, basketball, football and skiing, are typically candidates for ACL reconstruction surgery.

Others may be able to manage symptoms through physical therapy and strength training.

"The decision is based on more than MRI," Dr. Dragoo said. "We consider how stable the knee feels, the patient's activity goals and whether they want to return to sports that place a high demand on the joint."

What is ACL Reconstruction Surgery?

In most cases, surgeons do not repair the torn ACL directly. Instead, they reconstruct the ligament using a tissue graft, often the patient’s own tissue, called an autograft.

Common graft options include:

• Patellar tendon autograft - this procedure uses a portion of the patient's patellar tendon
• Quadriceps tendon autograft – this option uses part of the patient’s quadriceps
• Hamstring tendon autograft - this option uses tissue from the hamstring tendons

Surgeons work with patients to determine which graft best fits their anatomy, sport and recovery goals.

How Long Does ACL Tear Recovery Take?

ACL recovery is a lengthy process that typically lasts six to nine months, though timelines vary.

General milestones post ACL reconstruction include:

First two weeks

• Control pain and swelling
• Restore knee motion
• Begin early rehabilitation exercises

Six to 12 weeks

• Improve strength and mobility
• Restore normal walking patterns
• Continue physical therapy

Three to six months

• Advance strengthening exercises
• Begin running progression
• Introduce sport-specific movements

Six to nine months

• Complete return-to-sport testing
• Achieve strength and functional benchmarks
• Receive clearance for athletic participation

"Our goal is always to help patients return to the activities that matter most to them," Dr. Dragoo said. "Whether someone is a professional athlete, a competitive recreational athlete or simply wants to stay active, we apply the same evidence-based approach to treatment and recovery for all."

Learn more about Jason Dragoo, MD, and CU Medicine Orthopedics and Sports Medicine – Steadman Hawkins Clinic Denver

Frequently Asked Questions

Can you walk with a torn ACL?

Most patients can walk after an ACL tear, although the knee may feel unstable.

Is ACL reconstruction successful?

ACL reconstruction has a high success rate, particularly when combined with a structured rehabilitation program.

Can an ACL tear happen again?

Yes. A reconstructed ACL can be reinjured, but the change of reinjury is low (about 6%)

How long before I can return to sports?

Most athletes return to sports between nine and 12 months after surgery, depending on strength, function and recovery progress.

Is physical therapy necessary after ACL surgery?

Yes. Rehabilitation is a critical component of recovery and plays a major role in restoring strength, mobility and confidence.