ACL Injury: Does It Require Surgery?

The bone structure of the knee joint is formed by the femur, the tibia, and the patella. The Anterior Cruciate Ligament (“ACL”)  is one of the four main ligaments within the knee that connect the femur to the tibia.



Diagram of the knee.

The  anterior  cruciate  ligament  (ACL)  is  one  of  the  most  commonly  injured  ligaments  of  the knee.Treatment options for ACL injuries include both surgical and nonsurgical treatments.



When a patient with an ACL injury is initially seen for evaluation in the clinic, the doctor may also order X-rays to look for any possible fractures. He or she may also order an MRI (Magnetic Resonance Imaging) scan to evaluate the ACL and to check for evidence of injury to other knee ligaments, meniscus cartilage or articular cartilage.



In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability. This may be supplemented with the use of a hinged knee brace.

However, many people who are active, want to continue sports or just have a sense of “giving way” of the knee during every-day activites, are candidates for surgery.

The torn ACL is generally replaced by a substitute graft made of tendon. The grafts commonly used to replace the ACL include:

  • Patellar tendon autograft (autograft comes from the patient)
  • Hamstring tendon autograft
  • Quadriceps tendon autograft
  • Allograft (taken from a cadaver)

The goal of the ACL reconstruction surgery is to prevent instability and restore the function of the torn ligament, creating a stable knee.

Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining their motion after surgery. It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.

In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. . The graft is held under tension as it is fixed in place using interference screws, spiked washers, posts or staples. The devices used to hold the graft in place are generally not removed.

Arthroscopic view of ACL graft [yellow star] in position.



The  incidence  of  infection  after  arthroscopic ACL  reconstruction  has  a  reported  range  of  0.2 percent to 0.48 percent.

Rare risks include bleeding from acute injury to the popliteal artery and weakness or paralysis of the leg or foot.

A blood  clot  in  the  veins  of  the  calf  or  thigh  is  a  potentially  life-threatening  complication. A blood clot may break off in the bloodstream and may obstruct the veins of the leg or even travel to the lungs, causing pulmonary embolism or to the brain, causing stroke. This risk of Deep Vein Thrombosis is reported to be approximately 0.12 percent.

The  risk  of  infection  or  Deep  Vein  Thrombosis  are  both  significatly reduced  by  antibiothic therapy, physiotherapy and medicines preventing from blood clot formation.

Other  possible  knee-related  complications  include:  postoperative  pain  and  swelling,  pain  with kneeling, postoperative stiffness, patella fracture.

Recurrent instability and graft failure are seen in approximately 8 percent of patients.

Patients  treated  with surgical  reconstruction of the ACL have long-term success  rates  of 82 percent to 95 percent.


Physical  therapy  is  a  crucial  part  of  successful  ACL  surgery,   with   exercises   beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.


The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles. The patient may return to  sports  when  there  is  no  longer  pain  or  swelling,  when  full  knee  range  of  motion  has  been achieved,  and  when  muscle  strength,  endurance  and  functional  use  of  the  leg  have  been  fully restored.

The  patient’s  sense  of  balance  and  control  of  the  leg  must  also  be  restored  through  exercises designed  to  improve  neuromuscular  control.  This  usually  takes  4  to  6  months.  The  use  of  a functional  brace  when  returning  to  sports  is  ideally  not  needed  after  a  successful  ACL reconstruction, but some patients may feel a greater sense of security by wearing one.