The Knee: Explained for Athletes

by Jsantos, January 11, 2013

The Knee: Explained for Athletes

Many of Doctor Mead’s patients are athletes and one of the most common injuries he treats come from the knee. ACL tears among the most usual. Personally, I think we sometimes forget the real limitations of our joints and overuse them to the point of no return. Sometimes is too late and injuries arise.

Knowing the structure, design and functionality of the knee will help you understand how to train so you can avoid potential problems. This post comes from Frederick Hatfield; a physician specialized in training athletes. Check it out.

The Knee Structure

The knee joint is made up of the end of the femur and tibia bones. The ends of these bones consist of shallow convex surfaces into which semicircular shaped femoral condyles fit. Because of the shape, the bony stability of the knee is extremely weak. To improve stability many ligaments surround the knee joint. For example, the posterior cruciate ligament prevents forward displacement of the femur on the tibia. The medial and lateral ligaments provide stability on the medial and lateral sides. The knee joint is stabilized posteriorly by the popliteal ligament and anteriorly by the patella ligament.

The knee joint must allow movement yet be stable enough to absorb and withstand the forces created by the weight of the body and the force generated while participating in different activities. For example, the knee must counteract the negative landing forces in running and jumping and in weigh lifting exercises.

Because of the roles the knee must play, ligament and muscular stability assume important roles. For example, when the knee is extended it remains stable since it is surrounded by fairly taut ligaments from all sides and from within. However, when the knee is flexed some of the ligaments loosen to allow for a greater movement. Because of this, the muscular arrangement around the knee is extremely important in maintaining the stability needed to prevent injury.

The knee is stabilized on the anterior side by the quadriceps, on the medial side by the sartorius and gracilis, on the lateral side by the tensor fascia latae and on the posterior side by the hamstring muscle group from above and the gastrocnemius from below. Because of the small angle of attachment of the quadriceps to the tibia, a large stabilizing component is always acting on the knee joint. This is particularly important when the hamstrings are contracting strongly and the knee is flexed beyond 90 degrees at which point the hamstrings have a backward dislocating component. To counteract this force there is usually hip flexion, which serves to maintain hamstring length so that tension is maintained.

When the leg is bent 80 to 90 degrees or more and the sartorius, gracilis and gastrocnemius muscles contract, they create a dislocating component at the knee joint. From 180 (straight leg) to 90 degrees of flexion, most of the muscles crossing the knee provide a rotary and stabilizing effect. When knee flexion is less than 90 degrees, a dislocating component occurs in some of the muscles. The knee also has weak bony and ligament arrangements, which contribute to vulnerability.

The major movements that are possible in the knee joint are flexion and extension. Medial and lateral rotation takes place only when the knee is flexed. This allows the foot to turn when it is free to move, and the trunk to turn when the foot is fixed to the ground as for example, when wearing cleats or spikes. If rotation occurs when the leg is straight, it may cause knee injury.



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