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Knee Injury (cont.)

What Are the Types and Causes of Knee Injuries?

While direct blows to the knee will occur, the knee is more susceptible to twisting or stretching injuries, taking the joint through a greater range of motion than it can tolerate.

If the knee is stressed from a specific direction, then the ligament trying to hold it in place against that force can stretch or tear. These injuries are called sprains. Sprains are graded as first, second, or third degree based upon how much damage has occurred. Grade-one sprains stretch the ligament but don't tear the fibers; grade-two sprains partially tear the fibers, but the ligament remains intact; and grade-three tears completely disrupt the ligament.

Twisting injuries to the knee put stress on the cartilage or meniscus and can pinch them between the tibial surface and the edges of the femoral condyle, potentially causing tears.

Injuries of the muscles and tendons surrounding the knee are caused by acute hyperflexion or hyperextension of the knee or by overuse. These injuries are called strains. Strains are graded similarly to sprains, with first-degree strains stretching muscle or tendon fibers but not tearing them, second-degree strains partially tearing the muscle tendon unit, and third-degree strains completely tearing it.

There can be inflammation of the bursas (known as bursitis: itis=inflammation) of the knee that can occur because of direct blows or chronic use and abuse.

Anatomically, many of the structures that support the knee are interconnected. A knee that is injured may cause damage to one or more structures depending upon the mechanism.

Muscle Tendon Injuries, MCL and LCL Injuries, ACL Injuries, and Meniscus Tears

Muscle Tendon Injuries

Almost all of these strains are treated with ice, elevation, and rest. Sometimes compression with an Ace wrap or knee sleeve is recommended, and crutches may be used for a short time to assist with walking. Ibuprofen (Advil, Motrin) or naproxen can be used as an anti-inflammatory medication.

The mechanism of injury is either hyperextension, in which the hamstring muscles can be stretched or torn, or hyperflexion, in which the quadriceps muscle is injured. Uncommonly, with a hyperflexion injury, the patellar or quadriceps tendon can be damaged and rupture. This injury is characterized by the inability to extend or straighten the knee and a defect that can be felt either above or below the patella. Surgery is usually required to repair this injury.

Except for elite athletes, tears of the hamstring muscle are treated conservatively without an operation, allowing time, exercise, and perhaps physical therapy to return the muscle to normal function.

MCL and LCL Injuries

These ligaments can be stretched or torn when the foot is planted and a sideways force is directed to the knee. This can cause significant pain and difficulty walking as the body tries to protect the knee, but there is usually little swelling within the knee. The treatment for this injury may include a hinged knee brace that helps stabilize the knee and control range of motion. RICE (rest, ice, compression, and elevation) are the mainstays of treatment. Surgery may be an option for completely torn ligaments when the knee joint remains unstable after completing a course of rest and physical therapy.

ACL Injuries

If the foot is planted and there is force applied from the front or back to the knee, then the cruciate ligaments can be damaged. Swelling in the knee occurs within minutes, and attempts at walking are difficult. The definitive diagnosis may be difficult in the emergency department because the swelling and pain make it hard to test if the ligament is loose. Long-term treatment may require surgery and significant physical therapy to return good function of the knee joint. Recovery from these injuries is measured in months, not weeks.

Meniscus Tears

The cartilage of the knee can be acutely injured or can gradually tear. Acutely, the injury is of a twisting nature; the cartilage that is attached to and lays flat on the tibia is pinched between the femoral condyle and the tibial plateau. Pain and swelling occur gradually over many hours (as opposed to an ACL tear which swells much more quickly). Sometimes the injury seems trivial and no care is sought, but chronic pain develops over time. There may be intermittent swelling, pain with walking uphill or climbing steps, or giving way of the knee that results in near falls. History and physical examination often can make the diagnosis, and MRI may be used to confirm it. MRI is also able to define the where within the meniscus that the tear has occurred and its appearance. This may help guide whether surgery, physical therapy or both would be appropriate.

Medically Reviewed by a Doctor on 5/17/2016

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