Types and Causes of Knee Injuries

While direct blows 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 tear. Ligament stretching or tears are called sprains. These 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 it between the tibial surface and the edges of the femoral condyle, 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.

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

Acute knee injuries fall into two groups; those where there is almost immediate swelling in the joint associated with the inability to bend the knee and bear weight, and those where there is discomfort and perhaps localized pain to one side of the knee, but have minimal swelling and minimal effects on walking.