Long-Term Exercise After Knee or Hip Replacement

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 exercise after hip replacement? What about after knee replacement? Read further to learn the answers to questions like these, which are commonly asked by people who have had total joint replacement surgery.

Resuming an active lifestyle after surgery

More than 1.3 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.

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 about how active to be after surgery. Many, if not most, individuals want to resume the recreational and sporting activities that they had to give up before surgery. In a 2016 systematic review of 18 studies, the three highest quality studies reported that the percentage of people who return to sports after knee replacement ranged from 36 to 89 percent, with a trend toward lower-impact activities. Low-impact sports were resumed on average 13 weeks after surgery, while high-impact activities were delayed until six months after knee replacement.

In study of 420 individuals surveyed five years after hip replacement, 36 percent resumed their sports activities shortly after surgery, and this increased to 50 percent within five years. In a telephone survey of 62 patients younger than 50 years, the most common reasons for not resuming a variety of sporting activities after THR were fear of injury (29 percent) and physicians’ recommendations (26 percent).

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 different levels and types of physical activity affect a joint replacement and participants’ quality of life. Orthopedic surgeons, rehabilitation professionals, and researchers agree that regular exercise is important for all age groups. Unfortunately, the literature reveals that there is little to no increase in physical activity levels or decrease in time spent sitting one to two years after hip and knee replacement. Yet we know 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 are best.

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. Advances in polyethylene (high density and cross-linked) have markedly reduced this complication. Newer implant materials such as ceramic surfaces may result in less particle debris and longer life of hip replacements. However, this is still being studied. Whatever type of material is used in your replacement joint, the total wear and life of the joint depend 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. The 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 or off-road 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, but still far less than the commonly recommended 10,000 steps a day or 3.65 million a year.

Joint loads differ according to the type of activity you’re doing, how good your technique is and your body weight.

Knowing where to start

After surgery, you’ll have specific therapeutic exercises to do. This phase of your recovery will focus on helping you regain motion, strength, balance, 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, balance/coordination, and flexibility activities.

Short, daily bouts of exercise better than none at all

The American College of Sports Medicine, American Heart Association, and Centers for Disease Control and Prevention recommend that people with arthritis accumulate 30 minutes of moderate-intensity aerobic exercise three to five days a week. This means a total of 150 minutes each 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 you 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 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° to 100°. (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 series published in 2008 describes 31 individuals who returned to high-impact activities on average four times a week after knee replacement. Activities included jogging, downhill skiing, singles tennis, and basketball. An average of four years after surgery, all but one individual had excellent clinical outcomes based on self-reported function and x-rays of the replaced joint. The researchers concluded that while some patients will participate in high-impact sports with no short-term problems, such activities are inappropriate for most patients who have TKR. Most surgeons would agree with this assessment. In a 2007 survey, 92 members of the US-based Hip Society and 522 members of the American Association of Hip and Knee Surgeons (AAHKS) made recommendations for participation in sports after hip replacement surgery. The surgeons’ responses were classified as activities that were “allowed,” “allowed with experience,” or “not allowed.” If there wasn’t at least 75 percet agreement among the experts regarding a particular activity, it was classified as “undecided.” A similar survey was conducted in 2005 to gather surgeons’ opinions about returning to sports after a knee replacement and more recently in 2009 with 139 AAHKS members. This latter survey published in The Journal of Arthroplasty also considered the frequency of the activity. Activities such as swimming, walking and cycling on even ground, and golf were recommended for unlimited participation. High-impact activities including climbing, cycling off road, skiing on groomed runs, and doubles tennis were restricted to one to two times a month. It is important to note that these recommendations are based on experts’ opinions and not research evidence.

Talk with your health-care team

When you are talking to your surgeon and/or physical therapist about returning to a more active lifestyle after joint replacement surgery, you need to consider several factors. Here is a handy six-point checklist to use:

1. What type of procedure/implant did you have?

Guidelines for weight bearing in the early days after surgery may differ depending on what type of joint replacement procedure you have and whether you had any additional procedures (for example, a bone graft). Most individuals, however, are encouraged to put as much weight on their replaced joint as they can tolerate right after surgery. The type and location of the incision will affect what kinds of positions you will need to avoid in the first few weeks after surgery. 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 a now-routinely performed minimally invasive procedure with its two small incisions.

(Interestingly, 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.) It’s important to ask your surgeon about any precautions in positions or activities and for how long you need to follow them.

With a knee replacement, ask your surgeon what soft tissues (for example, ligaments) 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.

2. What about your bones?

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 to reduce your risk of falling.

3. 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 10 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. Joint forces calculated by direct measurement or implanted sensors in the replaced hip or knee joint provide the most reliable information and often lower values than determined by biomechanical models and gait laboratory data.

4. What about your weight?

If you are carrying extra weight, you are also placing extra stress on your new joint. Even with a low-impact activity such as walking, you place about two and half times your body weight through your hip and three times your body weight through your knee when you walk at three miles an hour. With every step you take, 20 extra pounds of weight produce 50 extra pounds of load at your hip and 60 extra pounds of load at your knee. If you are overweight, low-impact activities such as swimming, water aerobics, or stationary cycling might be best for you.

5. What is your 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. Many new exercise activities involve a learning curve. If you already have the knowledge, skills, and coordination you need to safely participate in a sport, it will be easier to return to it, and your surgeon is more likely to give it the stamp of approval.

6. When can you 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 at least three 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 risks of injury with this sport (for example, risk of falling or colliding with someone or something)?

• 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 an orthopedic surgeon

Orthopedic 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 doing deep knee bends or mountain hiking. This caution does not apply to a THR, in which 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 very shape of the hip, which is a ball and socket joint, 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 stability and the 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 — in fact, it is encouraged — whereas high-impact sports should be avoided or done infrequently. 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.

Want to learn more about exercising with arthritis? Read “Exercise 101: Finding the Right Exercise for Pain Relief” and “Time for Yoga: Yoga Benefits for Arthritis.”

Marie Westby is the physical therapy teaching supervisor at the Mary Pack Arthritis Centre and a clinician scientist at the Centre for Hip Health and Mobility in Vancouver, British Columbia. She acknowledges the contribution of Markus Kuster, MD, professor of orthopaedic surgery at the University of Western Australia and chairman of the Department of Orthopaedic Surgery at Kantonsspital in St. Gallen, Switzerland.

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