Risk Factors

ACL injuries are very common in the athletic population, but specific risk factors have been found that can increase a patient’s risk of injury.

Female athletes are 4 times more likely to sustain an ACL injury than male athletes. This is due to differences in anatomy, neuromuscular forces, ratio of quadriceps and hamstring muscle strength, and other factors currently under investigation.

Patients who play a sport that involves side to side cutting movements have an increased risk of sustaining an ACL tear. Soccer players have been found to be at a uniquely high risk of an ACL injury.

Patients who have a history of an ACL injury also have an increased risk of sustaining a second ACL injury, either to the previously injured knee or to the other knee

Symptoms

Patients may feel a pop in the knee during an ACL injury and will not be able to continue participating in activity. During the first 12-24 hours, patients will notice knee swelling and difficulty walking due to the swelling. Occasionally, patients may notice bruising around the knee. After the knee swelling subsides, patients will notice minimal symptoms to the knee. They will be able to walk normally and will not have much, if any, pain.

Diagnosis

ACL injuries are diagnosed using physical examination and imaging studies to confirm the diagnosis. The physical examination is used to identify areas of pain, swelling, change in range of motion, and laxity (or looseness) of the knee. X-rays are used to look at the bones of the knee. MRI (magnetic resonance imaging) is an important part of the diagnosis and will allow evaluation of all the knee ligaments, meniscus, cartilage, and any other structures that may have been injured.

Treatment

There is a common misconception that all ACL injuries require surgery to allow the patient to return to full activities. Treatment of an ACL injury should be individualized to each patient based on age, symptoms, associated injuries, and activity goals. Non-surgical treatment of ACL injuries can be used in patients who are active, but do not participate in cutting sports, or those who lead a less active lifestyle. Non-surgical treatment of ACL injuries can include:

Rest and activity modification: All sports and active pursuits should be stopped until the knee inflammation resolves. Occasionally, patients require several weeks of crutch use to regain a normal gait.

Non-steroidal anti-inflammatory medications (NSAIDs) can help decrease inflammation

Brace: Use of a knee brace can help the patient feel more confident and secure when walking

Physical therapy: This is an important tool to help you strengthen and retrain the muscles of the knee to work better together

Surgical treatment is recommended for young, active patients and those who participate in cutting or pivoting sports. Patients with an ACL tear who will undergo surgery will complete a course of physical therapy before surgery to work on decreasing inflammation, regaining normal knee range of motion, and leg strengthening exercises. ACL surgery usually occurs several weeks after the injury to ensure that normal knee range of motion is obtained. ACL reconstruction has been shown to be the most reliable surgery to allow a return to full activities with a stable and functional knee.

• ACL reconstruction is performed using arthroscopy and you will have small incisions that are used for the camera and specialized instruments

• Reconstruction of the ACL can be done with several different graft options which are discussed below

• Patients who receive an autograft (their own tissue) will also have an incision from where the graft is taken

• The graft is placed into tunnels that are drilled in the tibia and femur bones and is secured with screws or a metal button to hold the graft in place

• Patients are able to walk after the procedure on crutches (unless other surgeries are performed at the same time on the meniscus, cartilage, etc).

• Rehabilitation is a critical part of the recovery from an ACL injury and will focus on regaining quadriceps strength and symmetry to the uninjured leg

• Patients will undergo testing during their recovery to ensure that specific strength, range of motion, and functional metrics are being met

• Patients are able to return to full activities between 9-12 months after their surgery, depending on the results of the testing and a discussion with Dr. Kew

ACL Graft Options

The ACL can be reconstructed using several different graft types and we’ll discuss each one below. Autograft tissue is taken from the patient’s own knee, while allograft tissue is from a deceased donor. Graft selection is based on many factors, including patient age, activity level, and other factors.

• Bone-patellar tendon-bone autograft (BTB)

  • This graft is taken from the patient’s own knee and is harvested from the middle third of the patellar tendon (runs under the kneecap to the tibia) and includes bone pieces on each end that are taken from the bottom of the kneecap and top of the tibia

  • The BTB graft allows for bone to bone healing of the graft over time

  • This graft is the most commonly used graft in elite athletes and has the longest successful track record in orthopaedic literature

  • Some disadvantages to this graft include:

    • Knee pain with kneeling or patellar tendinitis after surgery can develop in some patients

    • Patients may experience higher levels of pain immediately after surgery due to the bone pieces that were taken from the patella and tibia

    • Larger incision is needed to harvest the graft

    • There is a small risk of a patella fracture after surgery. This is a rare occurrence, but is of great concern to surgeons

• Hamstring tendon autograft

  • This graft is taken from the patient’s hamstring tendons, which are located on the inside of the lower leg

    • Taking these hamstring tendons does not affect your ability to walk or participate in any activities or sports

      • Mild hamstring weakness has been noted in patients who are sprinters or those who require quick acceleration in their sport

  • Generally, 2 of the 3 available tendons are taken and weaved together to create a new ACL graft

  • Patients will have less pain than those who have a BTB graft and may be able to return to walking with a normal gait faster

  • The most important disadvantage to the hamstring graft is weaker initial fixation. The graft heals well over time, but initial physical therapy and activity should be carefully monitored to protect the graft

• Quadriceps tendon autograft

  • This graft is taken from the patient’s quadriceps tendon (runs from the thigh muscles to the top of the patella) and the central 1/3 of the tendon is taken

  • This graft can be taken with a bone piece from the patella or just as a soft tissue graft (no bone)

  • Quadriceps tendon autograft is the newest graft in the literature, but has been shown to be equivalent to the other autograft options. Due to its recent use, we don’t yet have long-term outcomes (>10-20 years) of patients who receive a quadriceps tendon autograft

  • Patients will have a similar postoperative pain course as patients who receive a hamstring graft

  • Quadriceps tendon autograft has a similar disadvantage as hamstring tendon autografts, as initial fixation is not as robust and early physical therapy will be monitored to protect the graft

• Allograft

  • This graft is taken from a deceased donor and several different tendon options can be used

  • Patients will only have the incisions required for the ACL reconstruction, as there is no graft harvest incision

  • Patients are able to return to walking normal and daily activities quicker due to the decreased pain and swelling after surgery

  • Disadvantages of using allograft tissue include:

    • Viral infection from the allograft tissue can occur, but is exceedingly rare and tissues are carefully sterilized and examined to ensure no viral transmission will occur

    • Studies have shown a significantly higher rate of ACL graft failure in young patients who participate in cutting and pivoting sports