Total joint replacements of the hip and the knee have become an extremely successful and relatively common way to relieve pain and restore motion to these joints. As a result of these successes, approximately 200,000 knees and hips are replaced annually in the United States. Because of their physical improvement after surgery, people who have a total joint replacement often expect to be able to participate in any and all types of activity. However, by engaging in certain strenuous activities, a patient can potentially destroy the artificial joint. As younger and younger people have joint replacements, failure of artificial joints is becoming an increasing problem. Although people who have a total joint replacement should limit their participation in some sports after surgery, they can participate in a wide variety of activities that will not damage their new joint.

Causes of failure
All joint replacements will fail if given enough time and activity. Most joint replacements fail because the replacement becomes loose or because of osteolysis (bone loss around the artificial joint). These two reasons for failure are intimately related and, for the most part, are due to wear of the joint's weightbearing surfaces. Wear of the joint generates debris. In response to this debris, osteolysis occurs and the replacement subsequently loosens. These failures may require surgical revision.

In people less than 30 years of age, the single most common factor in failure seems to be increased activity, such as participation in heavy labor, baseball, basketball, and running. Increased activity causes increased wear of the joint's weightbearing surfaces. In fact, about twice as many people under 40 as people in their 40s and 50s need revision surgery, and this need probably results from increased activity. Total hip and knee replacement can provide acceptable results in patients 30 to 50 years of age, and the results can be reasonably long lasting if patients avoid strenuous activity.

In impact-loading activities (such as jumping, running, and lifting more than 40 pounds), more forces than normal are placed on the implant (artificial joint). Impact loading also increases wear on the implant. Researchers have analyzed the forces generated in and around the hip and knee joints, including ground reaction forces, muscle forces, and joint reaction forces. For example, walking puts forces of approximately 1.2 times body weight on the implant. With running, these forces double to approximately 2.5 times body weight. In sprinting, the reaction forces are tripled to roughly 3.6 times body weight. The greater the forces, the greater the wear on the implant; therefore, forces should be minimized to minimize wear on the implant.

Alternatives to total joint replacement
People considering total joint replacement need to let their surgeon know what their postoperative goals are. If the goal is to become much more active, then the surgeon may be able to suggest an alternative type of surgery that is more compatible with the patient's expectations. These alternatives include lifestyle changes, the use of external supports, and medical management. Arthroscopic treatment (small camera and instruments inserted in the joint) may be an option if your symptoms are primarily mechanical (catching and locking); however, use of this treatment for joint disease is still debated among physicians. Arthrodesis (fusion of the joint) is an alternative form of hip treatment for young people who have disease in only one hip joint. Nonetheless, convincing people to try such an alternative is difficult because of the outstanding results of joint replacement.

Sports participation
For the most part, after total hip or total knee replacement, a patient can participate in low-impact sports, such as archery, bicycling, billiards, pool, bowling, cross-country skiing, fishing, golf, non-aggressive doubles tennis, horseback riding, hunting, low-impact aerobics, most shooting sports, rowing, sailing, scuba diving, swimming, and walking. Sports that generally are unacceptable after total hip or total knee replacement include baseball, basketball, climbing, downhill skiing, football, martial arts, parachuting, racquetball, running, soccer, sprinting, and volleyball. In general, if participation in a sport places undue stresses on the artificial joint, the patient should be a spectator at that activity rather than a participant.
Total joint replacement of the hip or knee is one of the most successful ways to relieve pain and restore function, but remember, you have to take care of the new joint so that it will last. Limiting sports participation to activities that put minimal stress on the joint will enable patients to be active without excessively increasing the need for more surgery.

Carlton G. Savory, M.D.
Columbus, Georgia

This article is adapted from "Total Joint Replacement Patients Should Stick to Low-Impact Sports," which originally appeared in BioMechanics 5(3):71-75, 1998.