Smooth Moves
Innovations Make Total Knee Arthroplasty A Popular Choice
By Philip J. Mycoskie, M.D.
Knee-replacement surgery is the most popular replacement surgery in the United States. The American Academy of Orthopedic Surgeons observes that more joint replacement surgeries, or arthroplasties, are performed on the knee than on any other joint.
In a total knee arthroplasty, also known as TKA, the diseased cartilage surfaces of the thighbone (femur), the shinbone (tibia), and kneecap (patella) are replaced by a prosthesis made of metal alloys, plastics, and polymeric materials.
Indications
Millions of people have undergone the procedure since it was introduced in its current form in the 1970s. In fact, some 200,000 to 300,000 knee replacement procedures are performed in the United States each year.
Most patients who undergo TKA are age 60 to 80 years of age, but the surgery has also been performed on patients as young as 16 years of age. It’s important for all patients to discuss alternatives - including physical therapy, medications, site-specific injections, or alternative surgeries - with their doctor before opting for TKA.
While TKA is the procedure performed most often (about 25% of all adults with osteoarthritic knee problems had some type of surgery in 1999), patients should not rule out arthroscopy, a less invasive surgical procedure that uses small incisions and miniature instruments, before discussing this option thoroughly with their physician.
Knee Basics
The knee is the largest joint in the body. It consists of the lower end of the femur, which rotates on the upper end of the tibia, and the patella, which slides in a groove on the end of the femur. Large ligaments connect to the femur and tibia to provide stability. The long thigh muscles give the knee strength. The knee acts as a hinge between the upper and lower parts of the leg. Its surfaces roll and glide as the leg bends.
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The first implant designs used the hinge concept and included a connecting pivot between the components. Things have changed since then, however.
The latest implants replicate the more complicated roll-and-glide movements of the knee. As many as three compartments are replaced during a TKA: the lower ends, or condyles, of the femur, the top surface of the tibia, and the back surface of the patella. Many components are designed so metal articulates against plastic, which provides smooth movement and results in minimal wear.
There are more than 150 knee replacement designs on the market today, and several manufacturers make knee implants. The brand and design used by a physician or hospital will depend on many factors, including a patient’s needs (based on his or her age, weight, activity level, and health), the physician’s experience and familiarity with the device, and the implant’s cost and performance record.
Coming Back from a TKA
Patients who have a TKA usually stay in the hospital for several days after the two-hour procedure. Once a patient returns home, he or she will have stitches or staples running along the wound or a suture beneath the skin on the front of the knee.
The stitches or staples are removed several weeks after surgery. A suture beneath the skin does not require removal. Most patients also experience some pain at night and during activity for several weeks after the operation.
Once home, patients can do several things to promote their recoveries. Eating a balanced diet, often with an iron supplement, promotes proper tissue healing and restores muscle strength. Exercise is another critical component of home care, particularly during the first few weeks after surgery.
In general, the recuperation period is short. Most patients are back up on their feet and able to return to work and resume most of their normal activities within three to six weeks following surgery.
Physical Therapy
Following knee implant surgery, physicians typically recommend physical therapy as well. A rehabilitation program will likely include a graduated walking program to increase mobility slowly, work on other daily activities such as sitting and standing and walking up and down stairs, and a program of specific exercises done several times a day to restore movement and strengthen the knee.
A physician may suggest working with a physical therapist at home or in a therapy center during the first few weeks after surgery.
One of the frequent concerns of TKA patients is when they can start driving again. In most cases, they can get back on the road when their knee bends enough for them to enter and sit comfortably in the car and when muscle control is adequate for normal braking and acceleration requirements. In general, most patients are back behind the wheel and driving within a month or two of surgery.