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Torn ACL and Reconstruction Surgery: Symptoms, Procedure Recovery

A complex set of tendons and ligaments help stabilize and support the knee joint with its every movement, from a simple walking step to an ice skater’s leap. Unfortunately, these tissues are vulnerable to injury. In particular, tears of the anterior cruciate ligament (ACL) are quite common, with between 100,000 to 200,000 occuring each year in the United States.


What is the ACL?

The anterior cruciate ligament (ACL) is one of four major ligaments in the knee joint. It helps maintain the knee's rotational stability and prevents the tibia (shinbone) from slipping front of the femur (thighbone).

The ACL is particularly vulnerable to injury during athletic activity or as the result of impact, and a torn ACL is a common injury in athletes of all levels. It is especially common in sports with a lot of leg planting, cutting and pivoting, such as soccer, basketball, skiing and football. Surgery is often required to repair an ACL tear.

Who tears their ACL?

People of all ages, physical condition and abilities can tear an ACL. Active women experience a higher incidence of ACL injuries then men because their biomechanics tend to put more stress on their knees.

ACL injuries are also common in children, especially as youth sports become increasingly competitive. Until recently, ACL treatment for children and adolescents was exclusively nonsurgical. This was because tradtional ACL surgery techniques could cause growing children to develop a leg length discrepancy or growth deformity. However, newer surgical techniques have made surgical repair an option for many kids and teens.

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

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


How do you tear your ACL?

A partial or complete ACL tear (rupture) often occurs during a sudden twisting movement, in which a person stops quickly and changes direction, especially while pivoting or landing after a jump.

A sudden, high-energy impact to the knee can also cause the ACL to tear. ACL tear injuries are often accompanied by injuries to other tissues in the knee, including cartilage or additional knee ligaments, such as the MPFL.

Knee joint interactive diagram - torn acl
View an interactive diagram of the anatomy of the knee and a torn ACL

Symptoms: What happens when the ACL is torn?

Common symptoms of a torn ACL include:

  • popping sound at the time of injury
  • pain
  • swelling
  • knee instability

When a person tears their ACL, they often report hearing a popping sound at the moment that the tear occurs. The knee will quickly swell and, in many cases, feel unstable. However, in some less severe tears, these symptoms may be mild. This is especially the case in people whose lifestyles do not involve intense physical activity.

If the ACL is completely torn, there will be instability in the knee that will cause feelings of sudden shifting or bucking. People will be unable to:

  • Jump and land on the knee.
  • Accelerate and then change directions.
  • Rapidly pivot on the knee.

What should I do if I think I have torn my ACL?

Immediately after an ACL injury, it is important to:

  • Stay off the leg and elevate it.
  • Decrease the inflammation in the knee by:
  • Consult an orthopedist or sports medicine physician as soon as possible.

The doctor will determine how bad the ACL injury is and review whether nonsurgical treatement and rehabilitation will be enough or if orthopedic surgery is necessary. Whether or not surgery is performed, physical therapy will be critical to strengthen the muscles surrounding the knee and improve its range of motion.

How is a torn ACL diagnosed?

A doctor can usually diagnose a torn ACL from a physical exam, although magnetic resonance imaging (MRI) is helpful. Getting an MRI is also important to find out if other parts of the knee have been injured.

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

When is ACL surgery necessary?

The choice to have surgery is usually based on the patient's lifestyle. In athletes and other people of any age who wish to continue doing physically demanding activity, an ACL reconstruction is often needed.

If the injury is not too severe, some patients who do not need to perform intense athletics or physical labor may be able go without surgery and still lead active, healthy lifestyles. Many people with torn ACLs who receive conservative, nonsurgical treatments are able swim, jog and use of most equipment found at the gym or health club.

Nonsurgical treatments

The main conservative treatments are rest and anti-inflammatory medication to reduce pain and inflammation.

Some patients may also be fitted with a leg brace for use during activities that place stress on the knee. The doctor will also prescribe a course of physical therapy. This rehabiliation regimen is extremely important for preventing future injury.

Possible disadvantages of nonsurgical treatments

The long-term outcome for patients who are treated nonsurgically varies. Those who return to unrestricted activity are likely to experience some knee instability. Pain may be associated with the physical therapy regimen. In the absence of an intact ACL – even when no other injury is present – the menisci (pads of cartilage that cushion the bones that meet at the knee joint) have a higher risk of injury. If a tear forms in one or both menisci of the knee, pain and swelling may occur. More importatnly, a damaged meniscus increases a patient's risk of developing osteoarthritis of the knee later in life.

What everyone should know about ACL surgery

Choosing the right treatment option for an ACL tear up-front can have lifelong implications. On behalf of Hospital for Special surgery, the world's largest academic medical center specializing in musculoskeletal health, the surgeon members of the HSS Sports Medicine Institute have drafted guidelines for people who are considering ACL treatment. Read the guidelines here.


How does ACL surgery work?

In most cases, it is not possible to repair or reattach a torn ACL. It must usually be completely rebuilt. ACL reconstruction surgery is performed arthroscopically.

The 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 is in 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.

At HSS, patients who undergo ACL reconstruction are usually given an epidural nerve block and remain awake during their surgery, rather than being placed 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.
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

Animation video: Torn ACL reconstruction

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

How soon should you get ACL surgery?

Reconstructive surgery is generally scheduled for between three and six-weeks after the injury occurs. This period is to allow 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 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.

Articles for further reading

Below, explore articles 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.

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