The Town Herald

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ACL Injuries

by [Thunder Cid]




The Anterior Cruciate Ligament (ACL) is one of the two cruciate ligaments of the knee, the other being the Posterior Cruciate Ligament (PCL). These ligaments are the stabilizers of the knee. The ACL is a strip of fibrous tissue, which is located deep inside the knee joint. It runs from the posterior side of the femur (thigh bone) to the anterior side of the tibia (shin bone) deep inside of the knee. The ligament is a broad, thick cord the size of a person's index finger. It has long collagen strands woven together in a fashion that permits forces of up to 500 pounds to be exerted. The function of the ACL is to prevent the tibia from moving in front of the knee and femur. The ACL also prevents hyperextension, (or extreme stretching of the knee backward) and helps to prevent rotation of the tibia.

The amount of knee ligament injuries has been on the rise in recent years. Over the last 15 years, ankle sprains have decreased by 86% and tibia fractures by 88%, but knee ligament injuries have increased by 172%. The injury usually occurs in either a slow twisting fall, a sudden hyperextension, or a sudden hyperflexion as when landing from jumping. When the injury occurs the athlete usually hears a "pop" and they will have immediate swelling of the knee. When the person tries to put weight on the leg it will feel like the knee isn't underneath the athlete. With most injuries the type of movement will help to determine the injury: "I twisted to the right." etc.

When ACL injuries occur there is a "popping" sound at the time of injury and swelling within six hours. An experienced clinician can diagnose an ACL tear with relative accuracy by a manual examination. X-ray examination and Magnetic Resonance Imaging (MRI) are also used in diagnosing ACL injuries. The knee joint will be instable and the athlete will have joint pain on the inner (medial) side of the knee. Doctors or trainers can use three different types of physical examinations: Lachman's test, Anterior drawer test, and Pivot shift test of MacIntosh.

Lachman's test is performed by having the athlete lie on his/her back, then passively flexing the knee of the athlete to between 20 degrees and 30 degrees. Make sure that the hamstring is relaxed or it can produce a false test result. Holding the lower part of the athlete's thigh in one hand and the upper part of the athlete's calf in the other, slowly pull the tibia forward. Increased looseness in the knee joint is indicative of an ACL injury.

During the Anterior drawer test the athlete lies on his/her back with the knee bent to 90 degrees and the foot resting on the table. Stabilizing the foot either by sitting on it or having someone else hold it down, the doctor will place his/her hands around the upper part of the calf with thumbs on the end of the thigh bone (tibal condyles), slowly applying pressure on the posterior side of the proximal tibia. Any looseness in the joint could indicate ACL injury.

The Pivot shift test of MacIntosh is conducted by having the athlete lay on his/her back. The foot of the injured side is lifted with the leg straight and the foot turned inward. Pressure is applied to the outside of the knee while the knee joint is slowly bent. An ACL injury is detected if the tibia moves out of joint at 30-40 degrees or if a clunk is felt. One should note that this test can be very painful for the athlete.

When an athlete has injured his/her ACL the initial treatment involves splinting the knee, ice treatment to help reduce swelling, elevation of the joint (just above the heart) and administration of anti-inflammatory drugs. The athlete also needs to limit physical activity. A non-athletic person can live with the injury using rehabilitation and bracing. When the ACL is injured the guide wire of the knee is gone, creating instability. Without the stabilizing actions of the ligament, there is increased wear on the top of the tibia, meniscal cartilages tear and the articular cartilage erodes. The erosion will result in degenerative arthritis with grinding and pain when climbing stairs, running or jumping. But for the active athletic person ACL reconstruction surgery is the only solution.

Repair of the ACL by surgery can be done by open or arthroscopic techniques. Recent advances in surgical techniques have made ACL repair much more predictable and less traumatic to the athlete. Techniques in arthroscopic surgery now allow surgeons to reconstruct the ligament through smaller incisions and several smaller "stab wounds" leaving less scarring. Techniques involve using the athlete's torn ligament strands and incorporating them into a primary repair of the ligament usually backed up by a portion of the athlete's patellar tendon. The patellar tendon's middle one-third is used with a block of bone from the patella and from the tibia. The graft is then passed through two tunnels drilled into the tibia and the femur. The bony portions of the graft are anchored using specially designed screws, giving a solid fix to the graft. The graft recreates the ACL and allows early motion and weight bearing. One problem knee injuries have is that ligaments and cartilage have little blood supply (vascularization). This means that they take longer to heal. Athletes can expect to return to competition nine to twelve months after surgery.

The repair of ACL injuries has a relatively high success rate. Approximately 1-2% of people will have some degree of dissatisfaction with their surgery. The leading causes of dissatisfaction are: arthrofibrosis (scar tissue), deep venous thrombosis (blood clots in leg veins), poor knee motion, infection and injury to the patella.

How can athletes prevent ACL injuries? Like most injuries they are not always preventable. Certain things can be done to help prevent the risk of injury. Strengthening the muscles around the knee that act as shock absorbers and joint stabilizers is of key importance. Strong thigh muscles will help keep the knee in position. Doing half squats or using a leg machine will work the thigh muscles. Running hills and stairs will strengthen both quadriceps and hamstrings. Riding a bicycle three times a week either indoors or outdoors will help. Make sure that the seat is high enough to avoid excessive knee bending. Water aerobics is also a great way to strengthen joints without a lot of stress. A knee bend resistive exercise program done by The United States Ski Team has resulted in an 80% decline in serious knee injuries. The program uses a single stance one-third knee bend going from 30 to 80 degrees at a steady rate for three minutes, working up to five minutes on each leg. Sport band (elastic cord) can be used to increase resistance when initial levels are achieved.

The anterior cruciate ligament is the main guide to knee stabilization. Fortunately injuries to the ACL are now much more treatable and athletes are returning to performance at a greater rate. All athletes need to be aware of the risk of ACL injuries but they also need to know if it does happen, it's not the end of their athletic career.



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