The knee joint

The knee joint

The knee joint is one of the largest, most complex, and easiest injured joints in the body. The mechanism allows for bending, stretching, and slight rotation. It is the joint which ultimately allows us to walk with a typical human gait, and allows sprinting and running, jumping, and intricate lower leg movements required by most athletic activities. The joint itself is complex because it has several tissues which work together to provide for its integrity. When we think of athletic injuries we usually visualize a skeletal model with the cruciate ligaments, the menisci cushions, and the muscles which pass over and behind the joint. In reality it is much more complex than this. The skin organ which encases it is a support structure. There are nerves and blood vessels which traverse the joint. The stability of the joint is reliant upon the many other ligaments than the ones usually mentioned in an injury report. There are the bursae which hold the fluid which lubricated the joint. The muscles from which the tendons emit are subject to the same tearing and stretching injuries as the ligaments.

The knee joint consists of four bones which articulate, or rub their specialized cartilaginous surfaces upon one another. The largest bone is the femur which has two distinct surface structures called the lateral and medial epicondyles. It has a groove for the patella, or kneecap, to guide upon it. The second bone of the joint is indeed the patella to which the large quadriceps muscle by is attached by tendonous insertion. This muscle, tendon, and bone cause the knee to straighten. The hamstring muscles cross the back of the joint and cause it to bend. The third bone of the joint is the larger leg bone called the tibia. It has two cartilaginous joint spacers called the medial and lateral menisci, upon which the tibial epicondyles ride. Finally there is the smallest leg bone called the fibula, which articulates with the parallel tibial bone at the knee. It is not uncommon for the fibula to develop a spiral fracture with abrupt twisting of the lower leg.

It is really pretty infrequent for the bones of the knee, expect for the fibula, to fracture. The bones are sturdy and large, and with the exception of major trauma, they usually stay intact. The usual site of the most disabling injured is the ligaments. The menisci are specialized ligaments, two in number, which act as cushions for the overriding femur. They can become torn, leading to exquisite pains with certain joint positions, or can leave fracture fragment which interfere with joint movement. The cruciate ligaments are located in the center of the joint. The anterior cruciate keeps the tibia from sliding forward and the posterior cruciate keeps it from sliding backward. If either of these is torn, the knee can collapse in certain positions. One thing about the knee ligaments is that they don’t heal as fast as other ligaments in the body, and total rehabilitation after injury can require nine months or more. The lateral collateral and medial collateral ligaments keep the knee from bowing out or in, and are likewise subject to injury.

Medical science has come a long way in the past several years. Whereas surgery used to require incisions of twelve inches or more, arthroscopy can now be done for most injuries. In this procedure a scope, the size of a larger needle is inserted in one part of the joint, and instruments are worked through a different puncture site toward the visualized area in order to perform the procedure. This can involve screwing a tendon down, laser shaping a torn meniscus or numerous other operative repairs. The puncture wounds heal quickly as opposed to lengthy haling of a linear surgical scar which often require splinting or a cast.

The other misery to which the knee is most often subject is osteoarthritis. Certainly one can get gout in a knee or rheumatoid arthritis or even a knee joint infection, but the most frequent malady is osteoarthritis. This is commonly called “wear and tear” arthritis. It can start early, as in a middle age, and be minimally symptomatic, but with age, weight gain, and inactivity it can become more and more disabling. It is caused by a gradual thinning and inflammation of the cartilages which are supposed to glide over one another. As the cartilage thins the bone ends become increasingly calcified. In the worst case scenario, there is bone on bone and essentially complete joint failure. As one might deduce, maintaining ideal body weight is one way to prevent its progression. Exercise, with special exercises to strengthen the muscles associated with the knee joint can be helpful. Medicines such as naproxen or ibuprofen can reduce the inflammation and pain. Finally, when people have irrevocable bone thinning and constant pain, total knee replacement may be done. About 300,000 total knee replacements are done in the United States each year, with about 60% being women. Physical therapy for a few months is required to gradually rehabilitate the knee, though shorter rehab times do occur.

So, love your knees and don’t abuse them. Watch your weight, and exercise regularly with low impact lower leg exercise. Talk to your doctor if knee pain or mobility is becoming a problem. Remember that is your knees are functioning poorly, all the stress, strain, and load goes directly to your lower back which is a problem all of its own.

John Drew Laurusonis

Doctors Medical Center