Skip to Main Content
Treatment Orthopedics

ACL Injury

Most ACL tears are treated with reconstructive surgery, but depending on the patient's age, degree of injury, activity level and recovery goals, a nonsurgical approach is sometimes chosen. Patients choosing between these options will benefit from a collaborative decision-making process with their doctors and physical therapists.

For patients who aren't very physically active or don't participate in sports that involve quick changes in direction, a physical therapy treatment plan (instead of ACL reconstruction surgery) is a reasonable option, as the injury may not interfere with their daily activities. The regimen takes six to 10 months and can restore knee stability to a point where it's close to the pre-injury state. Using a hinged knee brace (ACL functional brace) can help prevent episodes of instability during this period and support a safe return to low-stress sporting activities.

Unfortunately, many people who decide against surgery may experience a secondary injury to the knee due to repetitive instability episodes and altered biomechanics. Patients who have had an ACL tear that do not have ACL reconstruction surgery may be at a higher risk of further injury to the meniscus and cartilage. Rarely, some people with an ACL tear are able to participate in sports without symptoms of instability. This variability is related to the severity of the original knee injury, as well as to the specific activities an individual usually engages in.

Surgical treatment

The goal of surgical treatment is to restore stability to the knee. After a complete ACL tear, most patients can't participate in sports that involve pivoting or quick direction changes, and some experience instability even during everyday activities such as walking. Athletes can generally return to unrestricted activity and competitive sports 9 to 12 months after surgery, having completed an appropriate physical therapy program.

After the ACL injury and before any surgical treatment, patients may work with a physical therapist to restore motion and strength at the knee. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery due to scar tissue formation. It usually takes three or more weeks from the time of injury to achieve full range of motion. Injuries to other knee ligaments that occur along with the ACL injury – especially injury to the medial collateral ligament – may need to be braced and allowed to heal prior to ACL surgery.

The surgery to treat ACL injuries is called an arthroscopic ACL reconstruction. An arthroscope is an endoscope for use in joints, and in this minimally invasive procedure, the surgeon uses it to see inside the knee and pass surgical instruments through very small incisions. The procedure typically takes less than two hours but may be longer if the patient also has cartilage or meniscus injuries that require repair. Patients are usually under general anesthesia (completely asleep) and are given a nerve block (an injection that interrupts pain signals in the area and lessens post-op pain).

ACL tears aren't usually repaired by simply sewing the ligament's torn ends back together, because these repairs have been shown to fail over time. Therefore, the torn ACL is replaced or "reconstructed" using a graft (living tissue that will foster new growth) from one of the following sources:

  • Autograft (the patient's own tissues)
    • Patellar tendon
    • Hamstring tendon
    • Quadriceps tendon
  • Allograft (cadaver tissues)
    • Patellar tendon
    • Achilles tendon
    • Hamstring tendon
    • Tibialis tendon

Patients undergoing an autograft ACL reconstruction will have an additional incision, made to remove tissue from one of their own tendons. After surgery, patients return home the same day and use crutches initially and a knee brace for up to six weeks. Stitches are removed one to two weeks after surgery, and a physical therapy program is initiated around this time. Participation in physical therapy is key to ensuring a full recovery that includes getting back to sports and other physical activities.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.

Seeking care at UCSF Health

Expand Map

    Recommended reading

    ACL Reconstruction Surgery

    Considering ACL Reconstruction Surgery? Discover everything you need to know about preparation, the procedure itself and post-surgery recovery right here.

    Preparing for ACL Surgery

    The decisions you make and the actions you take before your surgery can be every bit as important as the procedure itself in ensuring a healthy recovery.

    After ACL Surgery

    Your rehabilitation program to restore range of motion to your knee begins the moment you wake up in the recovery room after ACL surgery. Learn more here.

    FAQ: Anterior Cruciate Ligament Surgery

    Frequently asked questions regarding Anterior Cruciate Ligament (ACL) Surgery including how long you will be on crutches, beginning physical therapy and more.

    Take Care of Your Knees

    Although collateral ligament injuries can be difficult to avoid, here are several steps you can take to improve the strength and flexibility of your knees.