> Skip repeated content

ACL Surgery

A torn ACL (anterior cruciate ligament) is a painful and potentially debilitating condition. ACL tears are very common. Each year in the United States, between 100,000 to 200,000 people tear their ACL. The ACL cannot heal on its own. Once torn, it will stay torn unless surgery is performed.


How do I know if I need ACL surgery?

For some patients – mainly older people and others whose lifestyles do not include running or other rigorous excercise – conservative, nonsurgical treatments may allow them to successfully return to their normal routines.

However, anyone who has torn their ACL and returns to unrestricted activity without an intact ACL will likely experience some knee instability. Most people with active lifestyles, especially those who participate in competitive sports or other rigorous athletic activities, will need surgery to return to their prior level of activity and avoid future injury.

MRI image of a healthy ACL.
Side-view MRI showing a healthy, intact ACL
MRI of Complete ACL Tear
Side-view MRI showing a completely torn ACL

Without an intact ACL, a person is also much more likely to tear their meniscus. The meniscus is a pad of cartilage that cushions the bones that meet at the knee joint. There are two menisci on each knee: the medial meniscus on the inside of the knee and the lateral meniscus on the outside. A torn meniscus will cause knee pain and, sometimes swelling. More importantly, however, a damaged meniscus increases a patient's risk of developing osteoarthritis of the knee later in life.

Most people with active lifestyles, especially those who engage in competitive sports, will need ACL surgery in order to reduce the risk of future injury.

What does ACL surgery do?

In most cases, it is not possible to surgically repair or reattach a torn ACL. Most often, ACL surgery involves a complete rebuilding of the ACL. This procedure, called ACL reconstruction, is the current standard of care for surgically treating tears of the ACL.

The surgeons at the HSS Sports Medicine Institute have drafted guidelines for people who are considering ACL treatment.

How does ACL surgery work?

In ACL reconstruction surgery, a new ACL is made from a graft of replacement tissue from one of two sources:

  • a portion of the patient's own hamstring, quadriceps or patellar tendon
  • an allograft (tissue from a human organ donor)

The type of graft used for each patient is determined on a case-by-case basis.

ACL reconstruction surgery is performed using minimally invasive arthroscopic techniques, in which a combination of fiber optics, small incisions and small instruments are used. A somewhat larger incision is needed, however, to obtain the tissue graft. ACL reconstruction is an outpatient (ambulatory) procedure, in which patients can go home on the same day as their surgery.

MRI of Complete ACL Tear
Side-view MRI showing a completely torn ACL
MRI of ACL rear reconstruction
Side-view MRI showing an intact, reconstructed ACL after surgery

At HSS, most patients who undergo ACL reconstruction are given an epidural nerve block during their surgery, rather than being placed fully unconscious under general anesthesia. This epidural is the same type of regional anesthesia many women receive during childbirth.

ACL reconstruction surgery steps

Reconstruction of the ACL follows a number of basic steps, although they may vary slightly from case to case:

  • The orthopedic surgeon makes small incisions around the knee joint, creating portals of entry for the arthroscope and surgical instruments.
  • The arthroscope is inserted into the knee and delivers saline solution to expand the space around the joint. This makes room for surgical tools, including the arthroscopic camera, which sends video to a monitor so that the surgeon can see inside the knee joint.
  • The surgeon then evaluates structures that surround the torn ACL, including the left and right meniscus and the articular cartilage. If either of these soft tissues have any lesions, the surgeon repairs them.
  • Next the graft will be harvested (unless a donor allograft is used). A section of tendon from another part of the patient's body is cut to create a graft, which is then attached at each end to plugs of bone taken from the patella and tibia. These plugs help to anchor the graft that will become the new ACL.
  • The surgeon inserts the new ACL into the femur and tibia using a flexible guide wire.
  • Screws are used to secure the plugs of bone. Over time, these plugs will be incorporated into the surrounding bone.
  • The surgical instruments are removed to complete the procedure.

Animation video: Torn ACL reconstruction surgery

Below, view an animation for a more detailed description of a minimally invasive ACL reconstruction.

How soon should you get ACL surgery?

ACL reconstruction is generally scheduled for between three and six weeks after the injury occurs. This allows inflammation in the area to subside. If surgery is performed too early, patients may develop a profound scarring response called arthrofibrosis.

Orthopedic surgeons gauge the appropriate timing of surgery based on:

  • whether there are other injuries present that need to be treated first
  • the physical appearance of the knee
  • the patient’s level of pain
  • the patient's range of motion and quality of muscle control when flexing (bending) or extending (straightening) the leg

What is the recovery time for ACL surgery?

It usually takes six to nine months for a patient to return to participating in sports after an ACL reconstruction, depending on the level of competition and the type of activity.

Patients are able to walk with crutches and a leg brace on the day of surgery. Very soon after surgery, the patient enters a rehabilitation program to restore strength, stability and range of motion to the knee. The rehabilitation process is composed of a progression of exercises:

  • Strengthening and range-of-motion exercises are started early in the recovery period.
  • Running exercises begin at about four months.
  • Pivoting exercises are started at around five months.
  • Return to playing competitive sports can begin as early as six months.

The degree of pain associated with ACL recovery varies and can be addressed successfully with medication. Recovery time also varies from patient to patient. The determination of when a patient has fully recovered is based on the restoration of muscle strength, range of motion and proprioception of the knee joint.

Arthroscopic surgical techniques have made recovery times quicker and easier, compared to when ACL construction was conducted through open surgery. But to achieve a successful outcome, it is critical to have the rehabilitation period carefully supervised by an appropriate physical therapist and to have follow-up appointments with the surgeon.

Additional articles and other content

Below, explore articles, blogs and other content on ACL injuries or select Treating Physicians to find the best doctor or surgeon at HSS to suit your specific condition and insurance.

How You Move video series: A youth athlete's story of ACL injury and recovery

In this video, a high school student and premier club soccer player from Fairfield County, Connecticut, discusses tearing her ACL and her journey back to competitive sports with clinicians at HSS Stamford.


Back in the Game patient stories

Blog posts

In the news

In-person and virtual
physician appointments

Urgent Ortho Care

Same-day in-person or virtual appointments

Specialized Centers, Departments and Services: