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The knee owes its great range of motion to the shallow socket of the upper tibia which meets with the ball–like end of the femur. The stability of the knee is provided by its restraining ligaments, most notably the medial and lateral collateral ligaments which prevent angulation of the joint medially and laterally, and the anterior and posterior cruciate ligaments, which prevent anterior and posterior displacement, respectively, of the tibia on the femur. Since the femur and tibia are not closely matched in shape, the knee cartilages, or menisci, are important in providing good contact between the bones. Any of the ligaments or cartilages can be injured, leading to instability, pain, and, eventually, arthritis.

Anterior Cruciate Ligament Injury
The anterior cruciate ligament is often injured in athletic and other types of trauma. When the ligament is ruptured, the knee is often unstable, with the anterior displacement of the tibia on the femur causing buckling episodes and can lead to meniscal injury and post–traumatic arthritis. If the knee is not satisfactorily stabilized by muscular conditioning and bracing, substitution of the ligament with tendon grafts taken from the patient's knee is undertaken. Ligament reconstruction done arthroscopically shortens the recovery period, but a return to strenuous or athletic activity must await several months of healing and rehabilitation to minimize the chance or re–injury.

Meniscus Injury
The menisci of the knee are rubbery, fibro–cartilaginous cushions which provide improved stability and gliding of the knee joint by virtue of their unique shape. Injuries of the knee can cause tearing of these cartilages. Only tears near the outer attachments to the tibia can heal if repaired. Tears in the other areas of the menisci, if they produce symptoms of pain, swelling, catching, or buckling, require arthroscopic removal of the unstable portion of the menisci. Often, the repairable meniscal injuries are found together with anterior cruciate ligament tears, which will also need to be reconstructed for the menisci to heal and avoid re–injury.

Posterior Tibial Rupture
The posterior tibial tendon runs behind the inside bump on the ankle (the medial malleolus), across the instep, and into the bottom of the foot. The tendon is important in supporting the arch of the foot and helps turn the foot inward during walking.

Causes of Posterior Tibial Rupture
Problems with the posterior tibial tendon seem to occur in stages. Initially, irritation of the outer covering of the tendon called the paratendon causes a paratendonitis. This simply indicates that there is inflammation around the tendon as it runs through the tunnel behind the medial malleolus.

As we age, a tendon is subjected to degeneration within the substance of the tendon. The term degeneration means that wear and tear occurs in the tendon over time and leads to a situation where the tendon is weaker than normal. Degeneration in a tendon usually shows up as a loss of the normal arrangement of the fibers of the tendon. Tendons are made up of strands of a material called collagen (think of a tendon as similar to a nylon rope and the strands of collagen as the nylon strands). Some individual strands of the tendon become jumbled due to the degeneration, other fibers break, and the tendon loses strength. The healing process in the tendon causes the tendon to become thickened as scar tissue tries to repair the tendon. This process can continue to the extent that a nodule forms within the tendon. This condition is called tendonosis. The area of tendonosis in the tendon is weaker than normal tendon. The weakened, degenerative tendon sets the stage for the possibility of actual rupture of the tendon.

Symptoms of Posterior Tibial Rupture
The symptoms of tendonitis of the posterior tibial tendon include pain in the instep area of the foot and swelling along the course of the tendon. In some cases, the tendon may actually rupture, due to weakening of the tendon by the inflammatory process. Rupture of the tendon leads to a fairly pronounced flatfoot deformity that is easily recognizable.

Diagnosis of Posterior Tibial Rupture
Diagnosis of posterior tibial tendonitis is usually apparent on physical examination. In some difficult cases, an MRI scan may be useful to determine whether the tendon has ruptured, (but this is seldom the case). The MRI (Magnetic Resonance Imaging) machine uses magnetic waves rather than x–rays, to show the soft tissues of the body. With this machine, we are able to slice through the area we are interested in and see the tendons and ligaments very clearly. This test does not require any needles or special dye, and is painless.

Treatment of Posterior Tibial Rupture
Treatment of posterior tibial tendonitis begins with a good supportive arch support. The arch support is useful because it supports the arch and takes some of the stress off the tendon. Anti–inflammatory medications, such as ibuprofen or aspirin, may be prescribed by your doctor. Cortisone injection in this condition is usually not indicated, due to the increased risk of rupture of the tendon following injection. Some physicians recommend a slightly different cortisone treatment (rather than injection) called ionophoresis.

Ionophoresis is a treatment that uses electric current to increase the absorption of a cortisone cream through the skin and down around the tendon where the inflammation is occurring. There is much less of a risk of rupture of the tendon when this method is used. If this fails to resolve the process, surgery may be required to remove the thickened tissue around the tendon. This is done to try and decrease the symptoms of pain and to prevent rupture of the tendon.

If the tendon has ruptured, surgery may be required to either repair the ruptured tendon–or to replace it with a tendon graft. Most tears will not be repairable, unless they have occurred only recently. Usually, another tendon in the foot, such as the tendon that flexes the four lesser toes (bends them down) is used as a tendon graft to replace the function of the posterior tibial tendon.

Finally, in cases which have been neglected, and a fixed flatfoot deformity is present, a fusion (or arthrodesis) of the foot may be required. A fusion is an operation where a joint between two bones is removed and the two bones on either side of the joint are allowed to grow together or fuse. This type of operation is used to stop pain from joints that are worn out and can be used to realign the bones when the normal mechanisms for maintaining normal alignment are lost–such as when the tendons and ligaments no longer work properly. Usually, several joints must be fused to control the flatfoot deformity occurring after posterior tibial tendon rupture.

Following surgery, you will most likely be placed in some sort of brace or cast if the tendon has been repaired or grafted. You will probably be in a cast for six to eight weeks if a fusion has been performed.

Total Knee Replacement
Arthritic Knee Cut Bone Prostheses in Place
Arthritic Knee Cut Bone Prostheses in Place

This illustration shows the knee during several stages of knee replacement.

Arthritis of the knees can be mechanical (osteoarthritis) in which the surfaces of the knee gradually “Wear out”. This may be due to either old age, angular deformity, or old fractures. Systemic arthritis such as rheumatoid arthritis or gout affects the synovium (the membrane tissue in the joint that normally lubricates the joint), becomes pathological and the surface of the joint is destroyed.

In either case when the surface of the joint is worn away, at a certain point in time walking and activities of daily living become very difficult. Standardized treatment such as weight loss, anti–inflammatory medication, braces, orthotics, steroid injections, physical therapy, etc. are all tried and if effective, that is fine.

In many cases, however, despite the above mentioned non–surgical forms fo treatment, functional limitations persist. Most people who have been considering knee replacement are limited to walking less than three to six blocks, or less than 15 to 20 minutes. They have difficulty getting up out of a chair. They have rest pain. Such people are usually on anti–inflammatory medication and/or pain killers on a regular basis and the pain is generally progressive. It is important to realize that a knee “Replacement” is actually just a “Resurfacing” of the knee joint. The femur or thigh bone is covered with a metal covering and plastic is placed on the tibia so that instead of irregular arthritic surfaces, one has metal and plastic articulating which produces a smooth non–patent surface. In most cases, the undersurface of the knee cap is also replaced with a plastic surface so that this articulates with the femoral surface.

Knee replacements have been performed since the early 1970s and our most recent designs appear to have about 85 per cent to 90 per cent survival rates for about 20 years. Knee replacements in 1998 were more successful than hip replacements with a lower incidence of revision. The actual procedure involving knee replacement involves either general or epidural anesthesia with a four to six day hospitalization. The surgery itself takes between 1–1/2 and 2–1/2 hours. In most cases, patients donate two units of blood to be used in the post–operative period. Weight–bearing begins immediately after the first post–operative day. Patients usually use a walker for a period of one to two weeks, going to crutches and then a cane. People are off all walking aids anywhere from three weeks to two months.

Success rates in knee replacements are approximately 90% with 10% not doing as well. This can be due to either stiffness or ache or swelling in and about the knee. The most significant complications, aside from general medical complications (heart and lung) involve infection of the prosthesis. If this occurs, in some cases, the prosthesis can be saved and the patient taken back to the operating room, the knee irrigated with antibiotic irrigation and then be on antibiotics. In some cases, if this does not respond, then the entire prosthesis must be taken out and antibodies given for six weeks and then another attempt at re–implantation of the prosthesis must occur. In an extremely small percentage of cases, conceivably if the infection could not be controlled, then one is left with a knee fusion in which the femur and tibia are fused into one bone.

Activities after knee replacement that should produce no difficulty are simple walking, bicycling, golfing, swimming. The prosthesis is not designed for impact loading sports such as skiing, basketball, racquetball. People have been known to play doubles tennis with bilateral knee replacements.