Elbow Issues

Anterior Cruciate Ligament Injuries (ACL)

Causes
The mechanism of injury for many ACL ruptures is a sudden deceleration (slowing down or stop), hyperex-tension, or pivoting in place. Sports-related injuries are the most common.

The types of sports that have been associated with ACL tears are numerous. Those sports requiring the foot to be planted and the body to change direction rapidly (such as basketball) carry a high incidence of injury. In this way, most ACL injuries are considered noncontact. However, contact-related injuries can result in ACL tears. For example, a blow to the outside of the knee when the foot is planted is the most likely contact-related injury.

Football is also frequently the source of an ACL tear. Football combines the activity of planting the foot and rapidly changing direction and the threat of bodily contact. Downhill skiing is another frequent source of injury, especially since the introduction of ski boots that come higher up the calf. These boots move the impact of a fall to the knee rather than the ankle or lower leg. An ACL injury usually occurs when the knee is forcefully twisted or hyperextended while the foot remains in contact with the ground. Many patients recall hearing a loud pop when the ligament is torn, and they feel the knee give way.

The number of women suffering ACL tears has dramatically increased. This is due in part to the rise in women’s athletics. But studies have shown that female athletes are two to four times more likely to suffer ACL tears than male athletes in the same sports.

Recent research has shown several factors that contribute to women’s higher risk of ACL tears. Women athletes seem less able to tighten their thigh muscles to the same degree as men. This means women don’t get their knees to hold as steady, which may give them less knee protection during heavy physical activity. Also, tests show that women’s quadriceps and hamstring muscles work differently than men’s. Women’s quadriceps muscles (on the front of the thigh) work extra hard during knee-bending activities. This pulls the tibia forward, placing the ACL at risk for a tear.

Meanwhile, women’s hamstring muscles (on the back of the thigh) respond more slowly than in men. The hamstring muscles normally protect the tibia from sliding too far forward. Women’s sluggish hamstring response may allow the tibia to slip forward, straining the ACL. Other studies suggest that women’s ACLs may be weakend by the effects of the female hormone estrogen. Taken together, these factors may explain why female athletes have a higher risk of ACL tears.

Symptoms
The symptoms following a tear of the ACL can vary. Some patients report hearing and/or feeling a pop. Usually, the knee joint swells within a short time following the injury. This is due to bleeding into the knee joint from torn blood vessels in the damaged ligament. The instability caused by the torn ligament leads to a feeling of insecurity and giving way of the knee, especially when trying to change direction on the knee. The knee may feel like it wants to slip backwards. There may be activity-related pain and/or swelling. Walking downhill or on ice is especially difficult. And you may have trouble coming to a quick stop.

The pain and swelling from the initial injury will usually be gone after two to four weeks, but the knee may still feel unstable. The symptom of instability and the inability to trust the knee for support are what require treatment. Also important in the decision about treatment is the growing realization by orthopedic surgeons that long-term instability leads to early arthritis of the knee.