John Tenny MD PA

The knee joint, as well as other joints in the body, are essentially hinges where two bones meet at a point where they can move with respect to one another. Each bone is covered with a material called articular or hyaline cartilage. This cartilage provides an extremely low friction surface that is incredibly durable. People can live active lifestyles for many decades before this articular cartilage show signs of wear. Knee replacement, or knee arthroplasty, is a procedure to resurface a knee when the articular cartilage is no longer functioning properly. In most cases, the articular cartilage is worn away from arthritis. In some cases, when only part of the knee is worn out, a partial knee replacement can be performed.







Modern knee replacement have been performed since 1968. Since that time, we have learned a great deal about the mechanics of the human knee and have incorporated this knowledge into designing better implants. Advances in material engineering has allowed manufactures to produce implants that wear less and last longer.

Patient undergoing knee replacement are typically in the hospital for four days. The procedure is performed the day of admission and therapy is started either the day of surgery or the day after. Some people go to a rehabilitation center after discharge from the hospital while others go directly home. After surgery the person will need to do exercises to gain motion and strength in their knee. When at home, it is important to elevate your leg when recumbent. The staples in the front of the knee are removed several weeks after surgery. The person's ability to perform daily activities gradually increases on a weekly basis. Many people return to their jobs between 6 and 12 weeks after surgery.

Knee replacements are mechanical devices that can wear out with time. Our goal is to have the joint replacement last the rest of the patient's life. Avoiding high impact activities such as running and jumping as well as carrying excess body weight can help prolong the life of the implant.

Another cause of implant failure is infection. Our bodies are constantly bombarded with bacteria that our kidneys filter out or our immune system eliminate. If these bacteria settle on a foreign material in our body, such as a knee replacement, they can form a biofilm which is an extracellular matrix that antibiotics cannot penetrate. When this happens, the joint replacement usually needs to be removed to treat the infection.

In some cases our bodies might be exposed to high levels of bacteria, such as when we have an active infection, a surgical procedure, or work done on our teeth. Under these conditions, we usually need to take an antibiotic that will cover the bacteria we might be exposed to.