The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee, especially among athletes. Approximately half of all ACL injuries occur in combination with other injuries, such as damage to the articular cartilage, meniscus or other ligaments. Bone bruises may be present beneath the cartilage surface and may be an indication of ligament damage.
The knee is a hinge joint, allowing the leg to bend back and forth without side-to-side motion. The knee is formed by a combination of bones, ligaments, tendons and cartilage. In an ACL injury, some of the important tissues are:
- Ligaments: which are tough bands of tissue that connect bones to each other
- Articular cartilage: which allows the bones to glide smoothly over each other with little friction
- Menisci: which act as shock absorbers in the knee
The knee joint is formed by three bones:
- Femur (thigh bone)
- Tibia (shin bone)
- Patella (kneecap)
The ligaments of the knee joint are:
- Medial collateral ligament (MCL)
- Lateral collateral ligament (LCL)
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
The ACL runs diagonally in the middle of the knee and connects the tibia to the femur. This structure provides stability to the knee joint, especially in front-to-back and rotational movement.
What Is an ACL Reconstruction?
An ACL tear is one of the most common knee injuries and the one that often requires surgery. When the ACL tears completely, stitching it back together (an ACL repair) is usually not possible, and has poor outcomes. An ACL reconstruction may be necessary to return to sports activity, restore knee joint stability and limit the future risk of cartilage and meniscus damage.
In an ACL reconstruction, a graft is used to replace the torn ligament. Most often, the graft is taken from the patient’s own body. This type of graft is called an autograft. The graft can be taken from various sites, such as the patellar tendon, hamstring tendons or the quadriceps tendon, in the knee. Additionally, a donor graft may be used, which is called an allograft. Your surgeon will discuss the pros and cons of each graft option and help determine which is the best choice for you.
ACL Injury Mechanism
Most ACL tears are non-contact injuries that often happen during sports and other activities that put stress on the knee. Some of the causes of an ACL tear are:
- Sudden change in direction (cutting)
- Pivoting on a firmly planted foot
- Poor/incorrect landing from a jump
- Stopping suddenly
- Receiving a direct blow to the knee (examples: fall on the knee, car accident, football tackle)
Women are more prone to ACL injuries than men. Athletes, especially soccer, football, lacrosse, field hockey and basketball players, are also at increased risk for ACL tears.
ACL Reconstruction Indications
Some indications of an ACL reconstruction are:
- An athlete with an ACL tear
- A patient with an ACL tear and other knee structures requiring repair, such as the meniscus or cartilage
- A non-athlete with an ACL tear and unstable knee
How an ACL Reconstruction is Performed
Before surgery, the main goals are to reduce pain and swelling, strengthen the leg muscles and restore full range of motion. Physical therapy is very helpful, and will often be prescribed by your surgeon. Performing an ACL reconstruction prior to achieving full pre-operative range of motion has a risk of post-operative knee stiffness and continued swelling.
General anesthesia with or without a nerve block is administered during the surgery. Then, the selected graft tendon is surgically removed (autograft) or thawed (allograft) and cut to the correct size for the patient.
The procedure is done arthroscopically, using small incisions and a special camera called an arthroscope. The camera is attached to a video monitor to guide the surgeon. An additional small incision allows use of the surgical instruments into the joint space. Arthroscopic surgery eliminates the need for a comparatively large incision as seen in an open procedure.
After examining the damage to the knee, the meniscus and cartilage injuries, if any, are repaired or trimmed. The surgeon will then remove the damaged ACL and reconstruct it with the healthy graft tendon. In the most common ACL surgery technique, holes are drilled into the femur and tibia to position the graft, which is then secured to the bones with screws or other fixative devices.
ACL Reconstruction Recovery
ACL surgery is an outpatient procedure. After the effects of anesthesia have worn off, another person may drive the patient home the same day. Medications may be prescribed for pain management, including non-steroidal anti-inflammatory drugs (NSAIDs), Tylenol, opioids and local anesthetics.
Other recovery techniques may include:
- Postoperative brace
- Ice bags or ice cooling machine
Physical therapy exercises will also begin immediately after surgery, as they are critical to the success of the procedure. Current physical therapy protocols for ACL reconstruction use an accelerated course of rigorous exercises. The goal after ACL reconstruction is to reduce knee swelling, regaining full range of motion, muscle strengthening and maintaining mobility of the kneecap.
ACL Surgery Recovery Time
During the first 10 to 14 days, the surgical wounds must be kept clean and dry. Regular applications of ice should be used to reduce swelling and pain. When pain and swelling have subsided, full range of motion has returned and muscle strength and endurance are restored, the patient may discuss return to playing sports with their surgeon.
Balance and control of the leg must also be present, usually taking about six months after surgery. Some sports activities require a longer recovery period before returning to play: nine months to a year.
A small percentage of patients experience surgical complications, which are a risk with any type of surgery. Complications of ACL reconstruction surgery include:
- Kneecap pain
- Bleeding at the surgical site
- Numbness of the leg
- Recurrent knee instability
- Stiffness of the knee
- Blood clot leading to pulmonary embolism (rare)
- Bacterial infection (very low risk)
- Poor healing of the graft
- Graft failure
- Rupture of the patellar tendon or patella fracture at site of graft harvest
Complications of ACL reconstruction are rare and outcomes are generally good. Most patients can return to their sport by the next season.
At University Orthopaedic Associates (UOA), our sports medicine surgeons have specialized training in ACL reconstruction. We have experience in treating ACL injuries in professional, collegiate and high school athletes, and can use these lessons to help you return to your sport. If you suspect an ACL tear or knee injury, call our office to make an appointment or fill out our appointment request form.