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When Do Acute Knee Injuries Require Surgery?

June 19, 2012

You don't have to be a professional athlete to suffer a painful acute knee injury, according to Dr. Russell Nord, an orthopedic surgeon and medical director of the Washington Township Orthopedic Surgery and Sports Medicine Center.

"Even though I specialize in sports medicine, most of my patients aren't necessarily athletes," he notes. "Acute knee injuries are more common, of course, among active individuals, including adults who are 'weekend warriors' and young people participating in various sports. Still, you can injure your knee doing something as simple as twisting awkwardly while working in the garden."

Two of the most common knee injuries involve tears in the meniscus cartilage or in the anterior cruciate ligament (ACL). "In about half of the cases where patients have torn the ACL, they also will have damage to a meniscus," says Dr. Nord.

Meniscal Tears

There are two menisci in each knee - one on the inner side, and one on the outer side. (See diagram.) They are C-shaped pieces of rubbery, tough cartilage that act as "shock absorbers" between the femur (thighbone) and the tibia (shinbone). They also distribute stress evenly throughout the knee and help keep it stable. Meniscal tears are more common on the medial (inner) side of the knee.

"The menisci are usually torn when you suddenly twist the knee, but sometimes it's hard to determine the cause," Dr. Nord says. "The most common symptoms are pain and swelling. Sometimes there is a 'catching' sensation or - in rare cases - the knee gets stuck in fixed position. If you're having sharp knee pain that seems to come out of nowhere, you may suspect a meniscal tear. You definitely should call your doctor if you are in severe pain or if you see no improvement within a week or so of treating the knee at home with the 'RICE' method of resting the knee, using ice and compression, and elevating the knee."

Diagnosing a meniscal tear involves a physical exam to pinpoint the site of the pain and an X-ray to eliminate other possible causes of pain, such as arthritis. If a meniscal tear is suspected, the physician may request a magnetic resonance imaging (MRI) study to get a clearer image of the soft tissue in the knee joint.

"We look at a variety of things in the physical exam, including tenderness at a specific point called the 'joint line,' which is between the femur and the tibia," he explains. "We also check for swelling, as well as pain when the knee is bent back all the way or when stressing the meniscus. Meniscal tears can happen to anyone at any age, but the risk increases with age since cartilage weakens over time. Meniscal tears are also more common in people who have osteoarthritis."

In many cases, meniscal tears that don't respond to the RICE treatment can be treated with cortisone injections and physical therapy.

"Unfortunately, in about half of the cases, surgery is required because the inner parts the menisci have a poor blood supply so they don't heal well," Dr. Nord says. "We can do a minimally invasive arthroscopic procedure, inserting a miniature camera and surgical instruments into the joint through very small incisions. Depending on the injury, we can trim away damaged cartilage if it is in an area without a good blood supply, or we can repair it if it is in an area with a good blood supply that allows it to heal."

ACL Tears

ACL tears are more common in younger, active people who compete in sports such as soccer or basketball or other activities that involve changing direction quickly, stopping suddenly or landing from a jump improperly.

"The ACL is one of the four main ligaments in the knee," notes Dr. Nord. "It is located right in front of the knee under the patella - also known as the kneecap. (See diagram.) The ACL provides stability and controls the back and forth motion of the knee. In addition to pain and swelling, a torn ACL can cause instability in the knee, which sometimes seems to slip out of place. People who tear the ACL may hear a 'popping' noise and feel their knee give out from under them."

Diagnosing a torn ACL involves a physical exam, during which the physician will check the knee's range of motion and whether or not the knee is loose and stretches more than it should. The exam also would include an X-ray to rule out fractures and arthritis.

"An MRI is another important tool in diagnosing ACL injuries," Dr. Nord adds. "Because it is soft tissue, the ACL doesn't show up on an X-ray. The MRI also can show whether the meniscus is damaged, which happens about half the time when the ACL is injured."

While some meniscal tears do heal with nonsurgical treatments, in active patients, the vast majority of tears to the ACL will require surgery.

"Torn ACLs usually can't heal on their own or be repaired, so we have to rebuild them from scratch," Dr. Nord explains. "We can do this using minimally invasive arthroscopic surgery, too. In most cases we will take ligament or tendon tissue from some other place on the patient's knee - such as the hamstring or patellar tendon - and use that to reconstruct the ACL. In other cases, particularly in patients over age 40, we can use tissue from a donor."

Minimally invasive arthroscopic surgery to repair either a meniscus or an ACL results in a quicker recovery than traditional "open" surgery with large incisions.

"With surgery to repair the meniscus, patients generally can expect a full recovery within a few months or even sooner if the cartilage is trimmed rather than repaired," says Dr. Nord. "Patients who undergo ACL reconstruction surgery generally can expect a full recovery within about six months if there are no complications and the patient follows the recommended physical therapy regimen."

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