KNEE JOINT - ANATOMY & FUNCTION
THE KNEE JOINT
Although the knee joint may look like a simple joint, it is one of the most complex. Moreover, the knee is more likely to be injured than is any other joint in the body. We tend to ignore our knees until something happens to them that causes pain. As the saying goes, however, "an ounce of prevention is worth a pound of cure."
If we take good care of our knees now, before there is a problem, we can really help ourselves. In addition, if some problems with the knees develop, an exercise program can be extremely beneficial.
The knee is essentially made up of four bones. The femur, which is the large bone in your thigh, attaches by ligaments and a capsule to your tibia. Just below and next to the tibia is the fibula, which runs parallel to the tibia. The patella, or what we call the knee cap, rides on the knee joint as the knee bends.
When the knee moves, it does not just bend and straighten, or, as it is medically termed, flex and extend. There is also a slight rotational component in this motion. This component was recognized only within the last 50 years, which may be part of the reason people have so many unknown injuries. The knee muscles which go across the knee joint are the quadriceps and the hamstrings. The quadriceps muscles are on the front of the knee, and the hamstrings are on the back of the knee. The ligaments are equally important in the knee joint because they hold the joint together. You may have heard of people who have had ligament tears. Problems with ligaments are common. In review, the bones support the knee and provide the rigid structure of the joint, the muscles move the joint, and the ligaments stabilize the joint. (Click HERE for a computer animation of basic knee motion (mpg file) courtesy of Rob Kroeger.)
The knee joint also has a structure made of cartilage, which is called the meniscus or meniscal cartilage. The meniscus is a C-shaped piece of tissue which fits into the joint between the tibia and the femur. It helps to protect the joint and allows the bones to slide freely on each other. There is also a bursa around the knee joint. A bursa is a little fluid sac that helps the muscles and tendons slide freely as the knee moves.
To function well, a person needs to have strong and flexible muscles. In addition, the meniscal cartilage, articular cartilage and ligaments must be smooth and strong. Problems occur when any of these parts of the knee joint are damaged or irritated.
For Additional Information on Meniscal Injuries: TORN CARTILAGE (MENISCUS)
There are two cruciate ligaments located in the center of the knee joint. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are the major stabilizing ligaments of the knee. In figure 4, on the lateral view, the posterior cruciate ligament prevents the femur from sliding forward on the tibia (or the tibia from sliding backwards on the femur). In the medial view, the anterior cruciate liagement prevents the femur from sliding backwards on the tibia (or the tibia sliding forwards on the femur). Most importantly, both of these ligaments stabilize the knee in a rotational fashion. Thus, if one of these ligaments is significantly damaged, the knee will be unstable when planting the foot of the injured extremity and pivoting, causing the knee to buckle and give way. (Click HERE for a computer animation of knee motion with the ACL intact in the joint (mpg file) courtesy of Rob Kroeger.) (Click HERE for a computer animation of abnormal knee motion without an ACL. The abnormal motion causes damage to the surface on the underside of the patella (mpg file). Courtesy of Rob Kroeger.)
For Additional Information on Anterior Cruciate Ligament Injuries: ARTHROSCOPIC ACL RECONSTRUCTION
THIS MATERIAL DOES NOT CONSTITUTE MEDICAL ADVICE. IT IS INTENDED FOR INFORMATIONAL PURPOSES ONLY. PLEASE CONSULT A PHYSICIAN FOR SPECIFIC TREATMENT RECOMMENDATIONS.
THE CENTER FOR ORTHOPAEDICS & SPORTS MEDICINE
1211 Johnson Ferry Rd
Marietta, GA 30068