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One of the most common injuries of the knee is an Anterior Cruciate ligament (ACL) tear or sprain, with approximately 200,000 ACL injuries a year in the United States. These injuries typically occur during sports participation when changing directions or abrupt stopping or jumping—for example in skiing, football, or basketball. The function of the ACL ligament is to keep the knee from over rotation and extending beyond the normal range of motion. This ligament connects the femur to the tibia and acts as a stabilizer in the knee. Swelling usually occurs quickly after an ACL injury and usually there is a popping sound in the kneecap when the injury occurs. An x-ray is performed to make a definitive diagnosis.

Some patients can recover from ACL injuries with rehabilitation. Injuries can be classified according to three grades with

  • Grade 1—trauma to the ligament is minor. Some of the fibers are stretched and this is called a sprain
  • Grade 2—Trauma to the ligament is more severe. A partial tear may be present where some of the fibers are torn
  • Grade 3—The fibers of the ligament are completely torn and this is a complete tear—the most severe ACL injury.

What is ACL reconstruction

ACL Reconstruction surgery is to repair a torn anterior cruciate ligament (ACL) and is performed by an orthopedic specialist.

The surgeon will remove the damaged ligament and replace it by grafting a piece of tendon into the knee. The tendon may come from the patient’s knee or a cadaver knee. The tendon is secured to the bones with fasteners or screws.

Indications for ACL Reconstruction

An ACL tear or injury is the main indication for ACL reconstruction surgery. An ACL injury most commonly occurs during sports that involve twisting or overextending the knee. Some causes of ACL injury include:

  • Direct blow to the knee such as during a football tackle
  • Sudden directional change
  • Slowing down while running
  • Landing from a jump incorrectly

Symptoms of ACL injury include

  • Knee buckle and/or loud popping sound
  • Swelling within a few hours of injury due to bleeding form ligament vessels
  • Unstable knee


ACL injury is diagnosed with a thorough physical examination of the knee by an orthopedic surgeon. Diagnostic tests such as x-ray, MRI and/or arthroscopy. Your doctor may perform various tests to see if the ACL is intact. Knees with a torn ACL may show increased forward movement of the tibia compared to a healthy knee during a Lachman test. Pivot test is another test to assess an ACL tear.

ACL Reconstruction Procedure

The goal of ACL reconstruction surgery is to tighten the knee and restore stability. Knee arthroscopy is performed under either local, spinal, or general anesthesia. An anesthesiologist will determine the best method.

  • The surgeon makes two or three small incisions around the knee.
  • An arthroscope (a narrow tube with a tiny video camera on the end, is inserted through one of the incisions to view the knee joint. This is connected to a monitor and enables the surgeon to view the inside of the knee joint.
  • A sterile solution is injected into the joint to expand it so that the surgeon can have a clear view inside the joint and space to work there.
  • Once the surgeon makes a diagnosis, miniature surgical instruments such as scissors, motorized shavers or lasers are inserted through the other small incisions, and the repair is performed based on the diagnosis obtained.
  • The surgeon makes an incision over the knee or hamstring area and takes out a part of the patellar, hamstring or quadriceps tendon to prepare the new ACL graft. Alternatively, a cadaver (allograft) may be used.
  • Small holes are drilled into the femur and tibia (upper and lower leg bones) where these bones come together at the knee joint. The holes form tunnels in the bone to accept the new graft.
  • The graft is pulled through predrilled holes in the tibia and femur.
  • The new tendon is fixed into the bone with screws to hold it in place while the ligament heals into the bone.
  • The incisions are closed, and a dressing is applied.

Post-operative Care

  • Leg may be elevated while resting to decrease pain and swelling.
  • Pain and inti-inflammatory medications may be provided for comfort
  • A physical therapist teaches specific exercises to strengthen the leg and restore knee movement. An individualized physical therapy program will be designed to help strengthen knee muscles and optimize knee function.
  • Periodic follow-up appointments will be scheduled to monitor healing and progress
  • Usually resume normal daily activities in a few months.
  • Return to work in 6 weeks if job is not too physically demanding. Longer recovery period may be necessary depending on physical demands of work.
  • Full recovery and return to sports may take 9 to 12 months
  • Avoid competitive sports for 5 to 6 months to allow the new graft to incorporate into the knee joint.

Risks and Complications

Anterior cruciate ligament reconstruction is a very common and successful procedure. It is usually indicated in patients wishing to return to an active lifestyle especially those wishing to play sports involving running and twisting. However, some risks and complications may occur such as

  • Pain and weakness in the knee
  • Stiffness and decreased range of motion
  • Bleeding
  • Infection
  • Blood clot
  • Athletic Orthopedics

    Athletic Orthopedics

    Athletic Orthopedics

    Athletic Orthopedics
    & Knee Center
    9180 Katy Freeway
    Suite 200
    Houston, TX 77055





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