Pain-Free Living

Give Your New Joint a Sporting Chance

by Marie Westby, B.Sc., P.T.

Now that you have a new knee or hip and can move around with considerably less pain, you may ask yourself, What’s next? Should you park this high-tech joint replacement in the garage and bring it out only for leisurely Sunday drives? Or should you take it out for a test drive and see how well it performs? How many miles can you put on your new joint? What kinds of activities can you engage in without damaging it — can you go walking, for example, or play tennis, or ride your bicycle? Read further to learn the answers to questions like these, commonly asked by people who have had total joint replacement surgery.

The context

More than half a million Americans undergo total hip replacement (THR) or total knee replacement (TKR) surgery each year. This number is growing as the population ages. Also, as surgical techniques and materials improve, younger individuals are beginning to seek out these procedures. This has led to a steady increase in the number of surgeries performed on people under the age of 55. (To learn more about knee and hip replacements, see our November-December 2004 and July-August 2005 issues.)

Osteoarthritis (OA) is the primary cause of knee and hip joint damage that leads to joint replacement surgery. Other factors include injuries, congenital problems, and rheumatoid arthritis (RA). Whatever the cause, joint damage brings pain and stiffness that leads people to cut back on their everyday activities, including sports and recreation. But cutting back on physical activity is a catch-22. Although it means that you place less stress on the damaged joint, it also means that you begin to lose muscle strength and bulk, increase the rate of bone loss, reduce proprioception (that is, your ability to sense the position and movement of your joints and limbs), and alter reflex responses in the muscles around the joint. These changes may lead to increased joint stress and pain, accelerated joint damage, and a greater risk of falls. Both research findings and common sense suggest that remaining active and maintaining good muscle strength and flexibility before surgery may mean a speedier recovery, less postoperative pain, and greater overall satisfaction with the surgery.

There is less agreement regarding how active to be after surgery. And many, if not most, individuals want to resume the recreational and sporting activities that they had to give up before surgery. A 2003 Australian survey of 216 people, carried out between one and two years after a hip replacement, found that the percentage of people participating in sports after surgery actually increased to 91% from a presurgery level of 87%. The activities weren’t necessarily the same, however. The most common activities after surgery were walking and water exercises; many people gave up golfing, tennis, and jogging.

In a study published in The Journal of Rheumatology in July 2004, researchers asked people to recall how active they had been since knee replacement surgery. The study, led by Dina Jones, Ph.D., found that people were able to engage in low-impact activities after knee replacement surgery without harming the new joint. The most commonly reported leisure activities were gardening and yard work (65%), walking for exercise (62%), and swimming (46%). What is really needed is a long-term study that does not rely on people’s memories but instead follows them for several years after their hip or knee replacement and monitors how being physically active affects a joint replacement. This has not yet been done. Orthopedic surgeons and researchers agree that regular exercise is important for all age groups. Exercise has numerous health benefits, such as reducing the risks of obesity, high blood pressure, heart disease, Type 2 diabetes, and osteoporosis. Resuming an active lifestyle after hip and knee surgery is also linked to improvements in cardiovascular fitness. The American Academy of Orthopaedic Surgeons suggests that exercise is important both in the recovery process and in the years after surgery. What we’re not yet sure of is just how active you should be and which specific exercises you should be doing.

Know your loads — know your limits

We do know that there is a limit to how much load and stress you can put on a new joint. Joint loads are the forces to which joints are subjected. One example is compressive force (weight pressing down on the joint). Another is shear force (sliding movement of the joint from side to side). Greater loads will increase the wear and tear on parts of your new joint — most notably on any parts made of polyethylene. Polyethylene is a very durable and rigid plastic, but polyethylene particles can break away from the implant and cause a body tissue response that leads to bone destruction. Newer implant materials such as metal-on-metal and ceramic-on-ceramic surfaces may result in less particle debris. However, this is still being studied. (Studies released in 2012 found that many metal-on-metal hip implants have a higher than acceptable failure rate and an FDA panel has since discouraged their use.) Whichever type of material is used in your replacement joint, the total amount of particles produced by wear and tear depends on at least two factors: (1) the number of steps you take (your activity level), and (2) the amount of load you put on the new joint. Number of steps and load affect wear differently. Double the number of steps, and you double the amount of wear. Just a small increase in load, however, can cause a large increase in wear. Factors like this explain why in a hip replacement with a plastic cup component, the cup wears anywhere from less than 0.1 millimeters (around 3/1000 of an inch) a year to 0.3 millimeters (around 1/100 of an inch) a year.

One way to understand wear in a total joint replacement is to compare it to wear on a car tire. The wear is influenced by the mileage (number of steps), the driving style (joint load), and the quality of the tire material (different implant surfaces, such as metal on polyethylene or ceramic on ceramic). It seems obvious that a tire can withstand a lot of mileage with a sensible and careful driver at the wheel. However, that same tire may wear out after only a few miles when a race car driver is behind the wheel.

The number of steps you take varies with different activities, and the range is very broad. Some individuals end up taking hundreds of steps a day, while others take many thousands. In one study, participants after THR averaged about 950,000 steps a year and after TKR 640,000 steps a year. That represents a lot of mileage.

Joint loads differ according to the type of activity you’re doing, how good your technique is, and your body weight. We’ll come back to this later.

Knowing where to start — the test drive

After surgery you’ll have specific therapeutic exercises to do. This phase of your recovery will focus on helping you regain motion, strength, and overall function in your replacement joint and your body as a whole. Eventually, you’ll be able to move on to recreational exercise and sports (although you may continue to do some of the therapeutic exercises as part of your overall fitness program). Your complete fitness program should include cardiovascular (aerobic), strengthening, and flexibility activities.

Is your engine in good shape?

The American College of Sports Medicine and American Heart Association recommend that people with arthritis accumulate 30 minutes of moderate-intensity aerobic exercise 3&ndash5 days a week. Even short bouts of just 10 minutes of exercise at a time will benefit your heart and lungs and help prevent health problems related to a sedentary lifestyle. If it has been many years since you were able to do aerobic exercise at an intensity that got your engine huffing and puffing, you need to find an activity that will allow you to start out slowly and thus pose minimal risk of injury. You can gradually work up to an intensity level that will give you the desired health benefits.

Strengthening the muscles around your new joint — as well as around the joints above and below — will help stabilize the joint, reduce stresses associated with weight bearing, and improve your balance and coordination. Along with some weight-bearing activity, strengthening exercises will also help maintain or even increase your bone density and improve the fixation and stability of your new joint. You need good baseline strength to perform some sporting activities safely and appropriately. Doubles tennis and cross-country skiing are examples of activities for which you need good leg strength and endurance.

You also need to consider the flexibility of your new joint. Flexibility refers to both the joint’s range of motion and the “stretchability” of the soft tissues surrounding or crossing the joint. If you’ve had limited joint movement for many years, your muscles are tight or short, making it especially important that you stretch them to achieve good flexibility and avoid strain. After a hip replacement, you may be able to flex (bend) your hip 100° to 110° or more and hopefully extend or straighten it completely. (The “normal” hip will bend up to 120°.) With a knee replacement, range of motion is often harder to regain. Some people are left with limitations in their knee movement and difficulty bending the knee more than 90°. (The “normal” knee will bend up to 135°.) How flexible your new joint and the joints above and below it are will influence what activities you can do. For example, if you want to ride a standard bike, you need to be able to bend your knees to about 110° and your hips to about 70°. If you can’t, cycling will strain the new joint and place extra stress on the joints above and below.

A case report published in 2003 described a 69-year-old man with hip replacements on both sides who returned to high-altitude mountaineering following intensive rehabilitation. The combination of excellent physical training, experience in the sport, and an intensive and careful rehabilitation program allowed him to be active at this elite level. The man’s surgeon concluded that individuals who have had a hip or hips replaced are, under specific circumstances, able to perform high-level sports such as mountaineering without signs of implant loosening or higher-than-normal wear and tear of the implant materials.

Not all surgeons would agree with this assessment. In 1999, 54 members of the US-based Hip Society and 58 members of the Knee Society were surveyed regarding their recommendations for participation in sports after joint replacement surgery. The surgeons’ responses were classified as activities that were “recommended/allowed,” “allowed with experience,” or “not recommended.” If there wasn’t at least 73% agreement among the experts regarding a particular activity, it was classified as “no conclusion.” (See: Activity Recommendations After Total Hip or Knee Replacement)

The six-point inspection

When talking to your surgeon and/or physical therapist about returning to a more active lifestyle, there are a number of factors to consider. Here is a handy checklist to use.

What type of procedure/implant did I have? Guidelines for weight bearing in the early days after surgery will differ according to what type of joint replacement procedure you have. If your implant is cemented, for example, the guidelines will be different from those for someone with an uncemented implant. In addition, the type and location of the incision will affect how soon after surgery you can move and what kinds of positions you will need to avoid. In a hip replacement, the more traditional single, large incision on the side of the hip may have a different effect on the rate at which you heal than the newer, minimally invasive procedure with its two small incisions. (Of interest, the limited research that has been done to date has not shown any real advantage of the “mini” approach over the traditional approach when it comes to rate of recovery and short-term improvement in function.) If your hip implant is made of the newer materials that are not yet widely used, such as ceramic-on-ceramic, less is known about their long-term success rates. It’s important to know first, what guidelines to follow for your particular kind of surgery and second, for how long you need to follow them.

With a knee replacement, ask your surgeon what soft tissues (for example, ligaments and tendons) were removed or repositioned and what this means for the stability of your new knee. Also, different knee implants allow for greater or lesser amounts of knee bend. Your surgeon can tell you what the limitations are for your particular knee replacement.

What about my bone? Low bone density or poor bone quality may affect the stability and life of a new joint. If you had a cementless procedure, the implant will only be stable if your bones are able to grow into it to hold it in place. Low bone density also places you at greater risk for breaking a bone if you fall. This fact will influence your choice of exercise activities. It also may mean that you should work with a physical therapist or personal trainer to optimize your balance, proprioception, and muscle strength in order to reduce your risk of falling.

What about joint loads and wear and tear? Joint loads differ by the type of activity, technique, and body weight. If you are riding a bicycle, for example, the potential loads on your hips and knees will be reduced if your bike is set up properly and your cycling technique is good. As a general guideline, common activities of daily living typically place three to four times a person’s body weight through the hip or knee joint. Sports activities can place five to ten times your body weight on these joints. See Typical Hip and Knee Joint Loads During Exercise for information about joint loads associated with common exercise activities.

What about my weight? If you are carrying extra weight on your body, you are also placing extra stress on your new joint. Even with a low-impact activity such as walking, you place more than four times your body weight through your hip and three times your body weight through your knee when you walk at 3 miles an hour. With every step you take, 20 extra pounds of weight produce 80 extra pounds of load at your hip and 60 extra pounds of load at your knee. If you are overweight, nonweight-bearing or very-low-impact activities such as swimming, water aerobics, or stationary cycling might be best for you.

What is my fitness level and sports experience? When thinking about your fitness level, you should consider your aerobic capacity, muscular strength, and joint flexibility. If you have been inactive, you should start out slowly to avoid straining or injuring yourself. Another way to put your new joint at less risk for injury is to choose a familiar sports activity. There is a learning curve for many new exercise activities. If you already have the knowledge, skills, and coordination needed to safely participate in a sport, it will be easier to return to it, and your surgeon is more likely to give it his stamp of approval.

When can I resume a particular activity? Some sports may require you to be further along in your recovery or rehabilitation program than others. If you need pretty good strength to participate safely, it may take several months after replacement surgery before you have regained the strength you lost during the time leading up to your surgery. Your surgeon may decide to check the stability and alignment of the implant by taking an x-ray before giving you the OK to resume a more active lifestyle. Generally, it is a good idea to wait three to six months after surgery before returning to sports. For golf, surgeons from the Knee Society recommend waiting about 18 weeks after a knee replacement before returning to the game.

Questions to ask yourself before deciding on whether to return to a sports activity or take up a new one include the following:

• How much enjoyment and fun do I (or would I) have doing this activity?
• If this is a new activity, what skills or training will I need so that I can engage in it safely?
• What are the costs involved? (Costs may include equipment, footwear, clothing, membership, transportation, and class or training costs.)
• How adaptable is this activity? For example, can it be done indoors in bad weather? Can I do it both alone and with a group? Can I modify it on days when I am more tired or have less time to exercise?

Advice from a top mechanic

Orthopaedic surgeon Markus Kuster, a leading researcher into physical activity after hip and knee replacement surgery, notes that “there is evidence that a balance exists between too little activity, leading to decreased bone density and early loosening within 10 years, and too much activity, leading to increased wear and later loosening after 10 years.” The key is to stay active while not tipping the scale on the side of overuse or injury. Another consideration is the specific shape or form of the replacement joint’s surface. Biomechanical studies have shown that in many knee replacements, there is less stress on the plastic part of the implant (atop the shinbone) when the knee is nearly straight than when the knee is deeply bent. For this reason, Dr. Kuster suggests being more cautious after a TKR when doing activities that place high joint loads on the knee when it is fully bent, for example, when jogging or mountain hiking. This caution does not apply to a THR, where stress on the plastic insert does not depend on the amount of bend in the hip.

Another factor to think about is the built-in stability of a hip or knee replacement. The hip is a ball and socket joint whose very shape provides stability. The knee, on the other hand, has poor stability on its own and needs ligaments and muscles to keep it steady and strong. Individuals generally recover faster after a THR than after a TKR and describe a more “normal feeling” in the replaced joint sooner. After a TKR, good muscle strength and coordination are needed to provide the needed stability and sensation of normal joint function. Dr. Kuster recommends that an individual who has had a knee replacement should work on both muscle strength and proprioception (for example, muscle coordination) before returning to sports. Physical therapists can teach you exercises to improve muscle coordination and other aspects of proprioception. These exercises will help you regain overall balance and reduce the risk that you’ll fall or injure the replaced joint.

Your driver’s manual

Current recommendations suggest that sensible participation in low- to moderate-impact activities after hip or knee replacement is OK, whereas high-impact sports should be avoided. How you use your new joint is up to you. But remember, a short-term lease allows you to return a used vehicle after putting on the mileage. Getting a joint replacement is the equivalent of making a long-term agreement, and it makes sense to try to avoid a visit to the dealership for a new model.

Last Reviewed August 22, 2012

Marie Westby is the Physical Therapy Teaching Supervisor at the Mary Pack Arthritis Centre in Vancouver, British Columbia, and a Ph.D. candidate in the School of Rehabilitation Sciences at the University of British Columbia. She would like to acknowledge the contributions of Markus Kuster, M.D., Professor of Orthopaedic Surgery at the University of Western Australia and Chairman of the Department of Orthopaedic Surgery at Kantonsspital in St. Gallen, Switzerland, and Dina Jones, Ph.D., Assistant Professor and Director of Clinical Research, Department of Orthopaedics at West Virginia University, Morgantown.

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