Osteoarthritis: How to Make Exercise Part of Your Treatment Plan
Nicholas A. DiNubile, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 7 - JULY 97
In Brief: The idea of exercising with swollen, painful joints and weakened muscles may seem counterintuitive. But increasingly research shows that the vicious cycle of immobility and dependence initiated by osteoarthritis can be interrupted by making exercise part of therapy. A well-designed program of aerobic and resistance training and whole-body flexibility and joint mobility exercise should join other interventions such as weight loss, medication, physical therapy, joint protection, and surgery to improve symptoms and reduce the impact of osteoarthritis on patients' lives.
Arthritis is the most common cause of disability in the United States (1), and osteoarthritis (OA) the most common kind of arthritis (2). While the etiology of the disease remains obscure, its prevalence clearly increases with age. Among the elderly, symptomatic OA is widespread, affecting an estimated one third of those older than 60 (3).
The disease process itself can affect one joint or several, with the weight-bearing joints—knees and hips—most often involved. Degeneration of articular cartilage appears to be the primary event, accompanied by secondary changes around the affected joint, such as muscle weakness and the growth of new bone, with resultant loss of mobility and function.
Consequences of Inactivity
Generalized immobility is a frequent sequela of OA. Pain leads to a reduced level of activity (4), and the disability often associated with the disease is largely an outcome of this process.
Some consequences of inactivity, including loss of muscle strength and the reduced production of proteoglycans in the cartilage within the affected joint, appear to accelerate the disease process itself (5). But other effects are global: declines in aerobic fitness and functional capacity. In one study, VO2 max was significantly lower in seven class 2 (normal activities despite pain or limited joint mobility) patients with OA of the knee than in six sedentary age-matched controls (6). In another study, significant decrements in exercise tolerance were observed in OA patients, and the extent of impairment correlated with the number of involved joints (7).
Reduced mobility increases the risk of weight gain (which in itself can accelerate OA of weight-bearing joints and exacerbate symptoms), and impairs activities of daily living. Ultimately, these patients are likely to become less independent and more socially isolated (8).
Osteoarthritis and inactivity constitute a vicious cycle: The less the joint is used, the weaker and stiffer it grows, the more overall aerobic capacity declines, and the more resistant the patient becomes to increasing activity. A well-designed program of exercise, applied as early as possible in the course of the disease, would logically seem to be a treatment of choice in this condition.
Working Out of the Vicious Cycle
Research has, in fact, shown exercise to be beneficial in several ways, affecting osteoarthritic joints both directly and indirectly, and improving patients' overall functioning. Among the direct effects are increased mobility of the joints and greater strength of the muscles that support and protect the joint, ameliorating pain and stiffness. Regular exercise has been associated with significant declines in joint swelling caused by arthritis (7).
These improvements should not be surprising, in light of the known effects of physical activity on joint physiology. Lacking blood vessels and nerves, the articular cartilage of the joint surface is nourished only by the diffusion of joint fluid through the cartilage matrix, a process that is driven mechanically. Movement of the joint is necessary to ensure proper nourishment and maintain integrity of the cartilage. Loading pressures within the physiologic range increase the rate of proteoglycan synthesis by mature cartilage cells (9), and inactivity decreases it. Clinically, mobilization is known to accelerate joint healing after trauma or surgery, whereas immobilization interferes with the healing process.
Joint mobility improvement. Loss of mobility in the osteoarthritic joint forces it to work at a biomechanical disadvantage, which in turn promotes fatigue and increases mechanical stress (4). Stretching and active and passive range-of-motion exercise are highly beneficial in improving or maintaining mobility and circumventing this process.
Joint protection. Resistance training to strengthen muscle around affected joints protects and stabilizes the joint, improving shock absorption and reducing stresses that can accelerate cartilage degeneration.
Weight control. Exercise may protect osteoarthritic joints indirectly by helping control body weight. The knee is subject to impact equal to three times body weight during walking (five times body weight while going up or down stairs or when running), and it has been observed that OA progresses more rapidly in overweight individuals. Researchers have consistently identified obesity as a risk factor for OA of weight-bearing joints, and one study (10) found that weight loss in middle-aged or older women significantly reduced the incidence of symptomatic OA of the knee. Although this study did not address the effect of weight loss once the condition has already been established, it did suggest that cartilage or subchondral bone may become particularly vulnerable to the effects of obesity in middle age and after.
Functional capacity maintenance. In addition, strength training (of lower body musculature in particular) may play a key role in maintaining functional capacity in older persons. In a study (11) of 1,122 individuals who were 71 years of age or older, objective measures of leg function were highly predictive of disability 4 years later. The authors suggested that strength training, along with interventions to improve gait and balance, might well be targeted to individuals who show declines in these areas, even if they are not yet disabled.
More fitness, less pain. Aerobic exercise for patients with OA has been shown to improve cardiovascular fitness, reduce symptoms, and improve functional capacity. One randomized, controlled study of 102 patients with knee OA found significant increases in 6-minute walking distance, and reductions in pain and the use of medication in a group that participated in an 8-week program of walking, other exercise, and education, compared with controls (12). Another found that 12 weeks of aerobic-level walking or aquatic exercise significantly improved exercise capacity and mood. The aerobic gains were maintained at 9-month follow-up, and improvements in flexibility and grip strength were also manifest at that time (13).
At least one recent study suggested that beneficial effects on functional capacity cut across exercise type, that is, the kind of exercise is less important than the fact of exercise per se. In the Fitness Arthritis and Seniors Trial (14), 439 adults with radiographically confirmed OA of the knee, pain, and physical disability were randomized to a program of aerobic exercise, resistance exercise, or health education. Three hundred sixty-five participants completed the 18-month trial. Those in the exercise groups showed modest but significant improvements in tests of physical performance (climbing and descending stairs, lifting and carrying 10 lb, getting in and out of cars), compared with the health-education group. They scored lower (better) on assessments of physical disability and self-reported knee pain.
What About Wearing Out?
On the other side of the OA-exercise ledger, concerns have persisted about the possibility that repetitive activity might promote or accelerate the disease. The literature here has been reassuring. For example, an 8-year study (15) of 451 members of a runners club and 330 community controls (ages at intake, 50 to 72 years) found no difference in the appearance or progression of OA between the groups. (The development of disability, incidentally, was significantly slower in the running group.) Also, a recently published study by Newton et al (16) found no evidence of any joint degeneration in an animal model in which dogs were exposed to a lifetime of regular, fairly intense running.
Exercise that subjects joints to abnormal stress, however, has been linked to OA. In a survey (17) of 117 former elite athletes, ages 45 to 68, OA of the knee was more prevalent in former soccer players and weight lifters than in runners or shooters. The authors speculated that the difference might reflect the deleterious effects of knee injuries (in soccer players) and high body mass (in weight lifters).
Overall, the weight of data suggests that in the absence of joint abnormalities, physical activity that remains within the limits of comfort and normal range of motion does not lead to joint injury (18).
Given the formidable base of research, it should come as no surprise that the guidelines (19) for the treatment for knee arthritis recently published by the American College of Rheumatology advocate exercise as part of initial management. Also, the American Academy of Orthopaedic Surgeons (Rosemont, Illinois), as part of its "Keep Moving for Life" program, recommends exercise as part of the overall treatment strategy for arthritis. One might go further and propose that exercise of some sort, whether it is limited to a single involved joint or extends to a balanced, overall program for general fitness, should have a role in treating virtually every patient who has OA.
The exercise prescription should have four aims: cardiovascular conditioning, improvements in strength, added flexibility, and increased joint mobility (see "Exercise for Osteoarthritis").
Cardiovascular conditioning. As with healthy individuals, aerobic exercise should aim to increase heart rate to the training range, ie, 60% to 80% of maximum, and keep it there for 30 minutes, at least three times a week. Low-impact exercise is generally best because it entails less risk of orthopedic complications and encourages compliance. The reduced cardiovascular risk may also be a consideration. A workout on a stationary exercise bicycle may be ideal for a patient with knee arthritis. When disease of weight-bearing joints is severe, swimming or water exercise has proven an excellent choice. In one study (13), patients with OA or rheumatoid arthritis improved equally with water-based aerobics and walking. The pool group had fewer sore and swollen joints and less morning stiffness.
Aerobic exercise must be matched to the patient's capacity. A seriously deconditioned individual may well start with walking sessions of 5 minutes or less, lengthened by no more than 10% per week. Patients may be more accepting of an exercise program if workouts are divided into short sessions. It has been found that three 10-minute aerobic sessions seem to be as effective in improving fitness and health risk profiles as a single 30-minute session (20). This has important implications in getting sedentary individuals motivated to become more active.
Resistance training. Strength training should work major muscle groups of the whole body, not only those that support affected joints (21). Muscles respond when given a load higher than accustomed, and any number of means may be used to this end: ankle weights and dumbbells, calisthenics, and simple devices constructed with elastic tubing, as well as more sophisticated machines. Patients can benefit without enrolling in a gym or spending heavily on equipment.
Whole-body strength training should be done at least twice a week, but no more than four times: A day must be allowed for recovery between sessions. Exercises to strengthen the muscles surrounding affected joints, however, are typically lighter, at least in the early stages, and in many cases—especially when there is extreme weakness or low exercise tolerance—may be prescribed every day. It is never too late to strengthen muscle. One study showed significant strength and function gains in 90- and even 100-year-old nursing home residents (22).
Flexibility and joint mobility. Stretching exercises for flexibility can safely be done every day. These should target all the major muscle groups, with particular attention to the calves, hamstrings, lower back, and front of the shoulders—the muscle groups that most commonly lose flexibility with age. Initially tight muscle groups may require special attention.
Joints affected by osteoarthritis require range-of-motion exercises (see next section): In the case of the knee, for example, 5 to 10 minutes of active, active-assisted, or passive flexion and extension are useful before strengthening or aerobic exercise (23). Stretching and range-of-motion exercises are particularly helpful when limited motion is the result of tightened muscles, tendons, and capsular structures.
Joint-specific exercise. Range-of-motion exercises can restore or increase mobility of affected joints beyond the results of simple stretching. These may require heat, ice, or other physical therapy modalities or assistance, at least in early stages. With severe joint involvement, gains may be slow. However, preventing further motion loss can be helpful. Forceful maneuvers must be avoided (4).
Individualizing therapy. The exercise prescription for OA should be flexible and multimodal, geared to the individual's capacity and modified for his or her specific deficits. With older, deconditioned patients particularly, the program should be monitored and should begin at very low intensity, progressing as the patient improves to maintain a level that balances challenge and comfort.
It is always important to keep individual impairments in mind, and to modify specific exercises accordingly. An individual with arthritis of the patellofemoral joint, for example, should not do full-range, isotonic leg extensions, which subject the patella to substantial stress. This patient may, however, be able to perform simple, short-arc leg lifts and straight-leg quadriceps isometrics.
Other Components of Treatment
The other principal therapeutic modalities for OA—weight loss, medication, surgery, and physical therapy—should be coordinated with exercise for best results.
Weight loss. Recent evidence suggests that OA progresses more rapidly in overweight individuals (10). Also, stress on weight-bearing joints decreases significantly with weight loss. However, many people find the challenge of significant weight loss overwhelming. It often helps them to know that even small losses result in significant force reductions across their joints. I tell my patients that for every pound they lose, their knees think they have lost 3 or 4 lb (see "Weight control" section, page 48). Even when I find early OA at the time of arthroscopy, I stress the need for weight control as part of overall disease management.
Medication. Appropriate timing of analgesics such as acetaminophen, aspirin, or other nonsteroidal anti-inflammatories will help patients get through exercise sessions more comfortably, and in some instances will help control joint inflammation. Analgesic requirements must be individualized; in many patients, exercise can lessen or eliminate the need for medication.
Physical therapy. Some patients need physical therapy to facilitate exercise and help control joint symptoms. Physical therapists can help modify exercise routines to be both comfortable and effective. They can also help educate and motivate patients, as well as objectively monitor their progress. In almost all cases, this should be considered a transition strategy. Ultimately, patients should be exercising on their own.
Therapists employ a variety of modalities. Electrical stimulation may strengthen muscles that have become too weakened or painful for independent exercise. Hands-on mobilization is sometimes necessary to break up adhesions and loosen tight tissue before independent range-of-motion exercise is possible.
Pretreatment with heat, transcutaneous electrical nerve stimulation, or other physical therapy modalities can reduce pain and stiffness enough to allow exercise. Ultrasound that penetrates deeply enough to increase collagen elasticity may be useful in the early stages of a flexibility program (24). Icing an affected joint for 15 to 20 minutes after exercise will reduce discomfort and minimize swelling.
Surgery. There have been tremendous advances in the surgical treatment of OA, including the use of arthroscopy, joint replacement, and other reconstruction procedures. Even in these surgical patients, exercise has an extremely important role. Both preoperative and postoperative exercise programs improve patient outcomes.
Postoperatively, especially after joint replacement surgery, many patients need the help of a physical therapist to begin remobilization, and a period of rehabilitation often must precede a regular exercise program. In my experience, exercise to strengthen muscles in the weeks or months before surgery can shorten and ameliorate the recovery process. This is extremely important in today's healthcare environment.
The Goal—and the Doctor's Role
Virtually every patient with OA can benefit from a well-designed, sensible exercise regimen. Physicians can have a tremendous influence in this regard. In addition to the initial diagnosis, exercise prescription, and analysis of balance with other therapy, physicians can:
Once OA patients have embarked on an exercise program that is tailored to their needs, most will be encouraged by results to maintain a regimen that enables them to live more fully and independently with their chronic condition.
This article was prepared by contributing editor Carl Sherman.
Dr DiNubile is an orthopedic surgeon in private practice in Havertown, Pennsylvania, specializing in sports medicine and arthroscopy. He is the director of Sports Medicine and Wellness at the Crozer-Keystone Healthplex in Springfield, Pennsylvania; a clinical assistant professor in the department of orthopedic surgery at the University of Pennsylvania in Philadelphia; the orthopedic consultant to the Philadelphia 76ers basketball team and the Pennsylvania Ballet; and a member of the editorial board of The Physician and Sportsmedicine. Address correspondence to Nicholas A. DiNubile, MD, Llanerch Medical Center, 510 W Darby Rd, Havertown, PA 19083.
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