ACL Tear & Reconstruction – Knee Ligament Injury
Introduction
The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments in the knee. Ligaments are strong non-elastic fibers that connect our bones together. The ACL crosses inside of the knee, connecting the thighbone to the leg. It provides stability to the knee joint.
ACL tears most commonly occur in very active people or athletes. The ACL can tear when people abruptly slow down from running, land from a jump, or change directions rapidly. These types of actions are frequently performed during sports, such as football, basketball, skiing, and soccer. Athletes are especially at risk for ACL tears, although they may occur in active workers and the general population as well.
The ACL can tear completely or partially. It is unable to repair itself. When the ACL is injured, it is common to see other surrounding knee structures damaged as well. Some cases of ACL tears are treated with non-surgical methods. However, there are several surgical options that successfully restore knee strength and stability.
Anatomy
The knee is structurally complex. Our knee is composed of three bones. The femur, or thighbone, sits on top of the tibia, the larger leg bone. The patella, or kneecap, glides in a groove on the end of the femur.
Large muscle groups in the thigh give the knee strength and stability. The quadriceps muscles are a large group of muscles on the front of our thigh that straighten and rotate the leg. The hamstring muscles are located on the back of the thigh and bend or flex the knee.
Four ligaments connect our knee bones together. The ligaments are strong tissues that provide stability and allow motion. The ligaments enable our knee to have the flexibility to move in various directions while maintaining balance. The medial collateral ligament is located on the inner side of our knee. The lateral collateral ligament is at the outer side of our knee. These two ligaments help the joint to resist side to side stress and maintain positioning.
The anterior cruciate ligament and the posterior cruciate ligament cross inside of the knee joint. These two ligaments help to keep the joint aligned. They counteract excessive forward and backward forces and prohibit displacement of the bones. They also produce and control rotation of the tibia. We rotate our tibia when we turn our leg outward to push off the ground with our foot. We use this motion to push off from the side when skate, run, or move our body to get into a car.
Two cartilage disks, called menisci, are located on the end of the tibia. The cartilage forms a smooth surface and allows our bones to glide easily during motion. The menisci also act as shock absorbers when we walk or run.
A smooth tissue capsule covers the bones in our knee joint. A thin synovial membrane lines the capsule. The synovium secretes a thick liquid called synovial fluid. The synovial fluid acts as a cushion and lubricant between the joints, allowing us to perform smooth and painless motions.
Proprioceptive nerve fibers are contained in the ligaments and joint capsule. The proprioceptive nerve endings send signals about body movements and positioning. For instance, the proprioceptors in the knee send signals to let us know how far to bend our joint in order to place our foot for a step. They plan and coordinate our leg movements whenever we move.
Causes
The ACL can tear during strong twisting motions of the knee. The ACL can also tear if the knee is hyperextended or bent backwards. People frequently tear the ACL while pivoting, landing awkwardly from a jump, changing directions suddenly, or abruptly slowing down from running. ACL tears occur most frequently in young athletes. Football, basketball, skiing, and soccer are sports associated with the highest injury rates.
Researchers show that female athletes have a higher rate of ACL injury than males in certain sports. They suspect the greater angles in the female hip and leg alignment may make the knee more vulnerable to force. Additionally, female hormones can relax ligaments and make them less stable, making some women more susceptible to knee injury.
It is common for additional injuries to result when an ACL tear occurs. Surrounding structures, such as the meniscus, cartilage, and ligaments can be injured as well. Some people may also experience bruised or broken bones. The ACL can tear during strong twisting motions of the knee. The ACL can also tear if the knee hyperextends or bends backwards. People frequently tear the ACL while pivoting, landing awkwardly from a jump, changing directions suddenly, or abruptly slowing down from running.
ACL tears occur most frequently in young athletes. Football, basketball, skiing, and soccer are sports associated with the highest injury rates.
Symptoms
People usually experience pain, swelling, and knee instability immediately after the ACL tears. Your knee may buckle or give out on you. You may not be able to fully straighten your knee. You may have difficulty moving your knee and walking. Typically, within a few hours the swelling in the knee increases dramatically.
Diagnosis
If you suspect you have torn your ACL, you should go to your doctor or an emergency room right away. A doctor can evaluate your knee by gathering your medical history, performing a physical examination, and viewing medical images. Your doctor will ask you about your symptoms and what happened if you were injured. Your doctor will examine your knee and your leg alignment. You will be asked to perform simple movements to help your doctor assess your muscle strength, joint motion, and stability.
Doctors typically perform the Lachman Test to determine if the ACL is intact. For this test, you will lie on your back and slightly bend your knees. Your doctor will place one hand on your thigh and attempt to pull your leg forward with the other hand. Your doctor will test both of your legs to compare the results. If you can move your leg three to five millimeters, the test is positive.
The Pivot Shift Test is another test to determine if the ACL is functioning. For this test, you will straighten your leg. Your doctor will hold your leg while turning it and moving it toward your body. If your leg moves in and out of position, the test is positive for an ACL tear.
Your physician will order X-rays to see the condition of the bones in your knee and to identify fractures. Sometimes a fracture or soft tissue injury does not show up on an X-ray. In this case, your doctor may order a magnetic resonance imaging (MRI) scan. An MRI scan will provide a very detailed view of your knee structure. Like the X-ray, the MRI does not hurt and you need to remain very still while the images are taken.
Treatment
Initially following an injury, your knee will be treated with rest, ice, compression, and elevation. You should rest your knee by not placing weight on it. You may use crutches to help you walk. Applying ice packs to your knee can help reduce pain and swelling. You should apply ice immediately after injuring your knee. Your doctor will provide you with a continued icing schedule. Your doctor may provide over-the-counter or prescription pain medication. In some cases, a knee brace may be recommended to immobilize and support the knee. A knee immobilizer is used for only a short period of time. Elevating your knee at a level above your heart helps to reduce swelling.
Treatment for ACL tears is very individualized. Many factors need to be considered, such as your activity level, severity of injury, and degree of knee instability. Treatments may include physical therapy, surgery, or a combination of both. The most likely candidates for non-surgical treatments have partial ACL tears without knee instability, complete tears without knee instability, sedentary lifestyles or are willing to give up high-demand sports, or are children whose knees are still developing.
Physical therapy and rehabilitation can help restore knee functioning for some individuals. Your physical therapist will help you strengthen your knee. Special emphasis is placed on exercising the quadriceps muscles on the front of the thigh and the hamstring muscles on the back of the thigh. Eventually, you will learn exercises to improve your balance and coordination. You may need to wear a knee brace during activities. Your therapists will educate you on how to prevent further injury.
Ultrasound Guided Platelet rich plasma injection or Stem Cells injection for regeneration is promising (not FDA approved) but supported by multiple Studies.
Prevention
It is important that you adhere to your exercise program and safety precautions when you return home. You should stay as active as possible. It is especially important to keep your quadriceps and hamstrings very strong. You should also continue to use the durable medical equipment as advised.
It is also important to avoid injuring your ACL again. Depending on your injury, your surgeon may provide you with temporary or permanent activity or lifting restrictions. In some cases, specialized knee braces may be recommended for specific activities.
