Strength Over Surgery

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April 2003

By C. Buz Swanik, PhD, ATC, and Dani Moffit, MA, ATC

The World Health Organization has declared 2000-2010 the “Bone and Joint Decade.” This initiative was inspired by a realization of the enormous individual suffering, morbidity, and economic and societal burden caused by musculoskeletal disorders. It is estimated that musculoskeletal conditions in the United States cost approximately $215 billion annually and that osteoarthritis alone costs $54.6 billion. Osteoarthritis (OA) is the most common systemic disorder in synovial joints and is characterized by degeneration of hyaline cartilage with secondary changes in bone and soft tissues.¹ More than 14 million people in the United States are affected and the knee is the second most common joint involved. Patients primarily complain of pain, instability, and decreased function.² The treatment of individuals with OA involves a basic knowledge of the cause of the disease, as well as the different treatments available, including proprioception and balance, strength training, and aerobic exercise. Although these treatments may not cure the disease, surgical intervention and ultimately total knee arthroplasty (TKA) can be delayed by incorporating exercise into the daily routine.

The etiology of OA is unknown, but various factors may contribute including age, obesity, sex, degree of physical activity, hypermobility syndromes, abnormal subchondral bone or bone mass, muscular disorders, or genetic factors.³ Recent evidence suggests that neurologic degeneration precipitates the onset of OA. It is theorized that the loss of joint sensations (proprioception) may cause small gait alterations, repetitive microtrauma, and ultimately excessive joint loading.⁴ The major symptom of OA is pain that arises with activity, which also later occurs at rest and is often nocturnal.^1,3 Stiffness from joint effusion and pain-induced muscle spasm are also common.¹ The prevalent treatment method for knee OA relies on symptom relief with anti-inflammatory drugs, yet this approach has little effect on disability or the disease process itself.⁵ There are studies that suggest that few primary care physicians recommend nonmedicinal treatments to their patients with knee OA, despite evidence that they can relieve pain, increase muscle strength, and decrease disability.⁶ It has been found that OA symptoms do not improve if attempts to alleviate pain through pharmacological or physical modalities are not accompanied by physical conditioning.⁷ Orthopedic procedures, such as surgery, for the osteoarthritic knee tend to have poor outcomes and are usually delayed because of the expense and inherent risks for a generally unsuccessful result.⁸ From this information, it can be inferred that there are possible treatments for OA that do not require medicinal or surgical intervention.

DISEASE PATHOLOGY

To determine optimal treatment protocols for OA, a foundational understanding of the underlying pathology of the disease should exist. Proprioception and balance are important aspects of OA treatment because of their strong correlation with function in the knee.⁴ Balance is often used to assess functional joint stability. It is influenced by the same sensory information that mediates joint proprioception and is partially dependent on the inherent ability to integrate joint position sense with neuromuscular control. This neuromuscular control is mediated by the peripheral mechanoreceptors within articular and tenomuscular structures by conveying joint motion and position sense to the individual. The sensory information is then translated into coordinated muscle activation strategies necessary for dynamic restraint and motor control. As joint degeneration progresses, the tension on soft tissue is altered and an unequal distribution of joint loads causes the articular surface to break down. Pain, effusion, and joint laxity diminish proprioceptive awareness and in the lower extremity this may lead to deficits in balance.⁴ This loss of balance can be the precursor to falls, especially in the elderly, leading to broken bones and other injuries.

The reliability of the sensorimotor systems is necessary for the production of a smooth gait. During the simple course of walking, harmful transient forces at heel strike should be attenuated by accurate timing and placement of the lower limb on the ground with eccentric quadriceps contraction.⁸ Without the conscious awareness of joint motion and position in the knee, the placement of the lower extremity during ambulation is affected. Dynamic stabilization within the joint is compromised because the preparatory and reflexive muscle activation is diminished. Conscious proprioceptive awareness is necessary for coordinated neuromuscular control.⁴ When a sensorimotor dysfunction exists, an abrupt jarring of the leg at heel strike will occur, initiating or perpetuating arthritic damage.⁸

STRENGTH TRAINING

Quadriceps sensory dysfunction, such as diminished proprioceptive acuity, has been demonstrated in patients with knee OA and has been proposed as a factor in the pathogenesis or progression of the condition. Joint rehabilitation and physical activity can improve proprioceptive acuity.⁸ Patients with OA often have weaker leg muscles, especially in the quadriceps, than persons without evidence of a degenerative disease.^6,8 Moreover, the degree of quadriceps weakness has been associated with the degree of pain in the knee and the amount of physical disability. Muscle weakness may produce an unstable joint, which in turn leads to strain on innervated tissues. This is responsible for pain and disability. The person will likely avoid activity to decrease pain, resulting in disuse muscle atrophy and further weakness, creating a circle of disuse, muscle weakness, and disability.¹ In a study by Ettinger and Afable, resistance training of the quadriceps increased strength, decreased knee pain, and improved physical function in persons with OA.¹ Other recommendations include strengthening for both the quadriceps and hamstrings.³ It has been shown that an increase in quadriceps strength is associated with improved functional performance, which may delay or avoid the need for surgical intervention.⁸

AEROBIC EXERCISE

Along with resistance training, aerobic exercise has been promoted as an alternative method to reduce pain and functional disability due to knee OA. Literature focused on persons without symptoms of OA suggests that low-intensity aerobic exercise can be as beneficial to improving physiological status as high-intensity exercise.⁷ In the case of patients with OA, this can be positive. By including low-intensity aerobic exercise in their daily lives, patients with OA garner many benefits. For example, in short-term studies, patients with knee OA have shown improvement in physiological parameters, pain, and disability. Therapeutic exercise also has other positive health benefits including improved mental health, as well as preventive measures for coronary heart disease, non-insulin-dependent diabetes, and osteoporosis.¹ Hurley and Scott demonstrated that a 5-week exercise program, including isotonic and aerobic training, improved quadriceps motor and sensory function, including strength, voluntary activation, and proprioceptive acuity.⁸ It also reduced disability in patients with knee OA. Preliminary studies by Mangione et al illustrated that people with OA can safely perform aerobic exercise and obtain a training effect, improve functional status, and decrease disability and pain. In the study, the participants were involved in a 10-week stationary cycling regime, with the seat height adjusted to limit knee flexion and minimize pedal load. This decreased joint stress may have contributed to the positive finding of the study.⁷ However, many aspects of aerobic training for patients with OA remain unknown. It has not yet been determined which type of exercise is most beneficial, as well as the optimum frequency, intensity, and duration of exercise to produce the greatest functional improvement with the least amount of pain.^1,7 Additionally, concern still exists as to whether the exercise accelerates the underlying disease.¹

STAGES OF TREATMENT

The treatment of OA can be compared to the rehabilitation of an acute injury because patients will often present with pain, joint effusion, muscle weakness, and dysfunction. There are four basic stages to consider. Each stage has its own goals and the stages may overlap. This allows work in the stage of most comfort, regardless of where the patient may be in treatment.

The goal of stage one is the reduction of pain, swelling, and inflammation. This can be accomplished through the use of cryotherapy, aquatherapy, and anti-inflammatory and/or analgesic medications. Pain control is paramount if the patient is to perform any type of low-intensity, short-duration therapeutic exercise. Simple non-weight-bearing joint-repositioning tasks (heel slides) and balance exercises on an unstable surface (foam) can begin to restore joint sensations.

The second stage involves concentric, mostly nonfunctional, exercises. These may include the use of electromyographic biofeedback to facilitate quadriceps muscle recruitment.² Biofeedback has been documented to be a valuable aid to an exercise program, enhancing motivation as well as muscle strength, tolerance, and flexibility.² The patient can use biofeedback for learning how to initiate muscle contraction, rather than relying on electrical stimulation machines. A common exercise that can be used during this stage is short arc quads (SAQs). Biofeedback may be used in conjunction with SAQs to help the patient’s awareness of the muscle contraction. Joint repositioning can be included by using a goniometer. Applying loads to a joint can make proprioception tasks more difficult but may also stimulate sensory pathways.

Stage three includes the building of both strength and endurance. Isotonic exercises, such as quadriceps extensions and hamstring curls, should be incorporated to aid in the development of quadriceps and hamstring strength. The benefit of isotonic exercises can be twofold. Not only do isotonic exercises increase muscle strength, but they can cause muscle hypertrophy. One contributing factor to OA is being overweight. An increase in muscle mass can aid in weight loss because of the metabolic cost associated with maintaining muscle tissue even when the patient is not exercising. Proprioceptive exercises that concentrate on balance and dynamic joint stabilization should be utilized at this time.² Exercises as simple as bipedal balancing with eyes closed or balancing while playing catch may prove beneficial. It is important to emphasize safety, but consider that the sensorimotor system will not improve if balance tasks are too easy. As the patient is able to tolerate the increasing resistance during isotonic training, the progression to cardiovascular exercise machines should occur. Literature has shown that exercise on a traditional stationary or recumbent bike can provide a training effect, as well as minimize pain, joint loads, and disability in the knee.⁷

Stage four is simply to maintain an increased level of daily living activities. The patient needs to find a balance between strength and endurance with daily exercise.² Compliance may be especially difficult and patients should be educated to expect frequent retreats to previous stages as a natural progression of OA. Stage one should be incorporated daily, but stages two and three can be continued as necessary. Strength training may plateau and balance exercise can include single leg stance on unstable surfaces, depending on the level of joint instability. By maintaining the gains made in the previous stages, the patient will ultimately delay possible surgical interventions in the future.

C. Buz Swanik, PhD, ATC, is director, Biokinetics Research Laboratory, and assistant professor, Department of Kinesiology, Graduate Athletic Training/Sports Medicine, and Dani Moffit, MA, ATC, is a doctoral student, Department of Kinesiology, Athletic Training/Sports Medicine Program, Temple University, Philadelphia.

REFERENCES

Ettinger WH Jr, Afable RH. Physical disability from knee osteoarthritis: the role of exercise as an intervention. Med Sci Sports Exerc. 1994;26:1435-1440.
Swanik CB, Rubash HE, Barrack RL, Lephart SM. In: Lephart SM, Fu FH, eds. Proprioception and Neuromuscular Control in Joint Stability. Champaign, Ill: Human Kinetics; 2000:323-338.
Handy JR. Osteoarthritis in elderly knees. South Med J. 1996;89:1031-1035.
Vad VB, Bhat AL. The athlete with early knee arthritis. Phys Med Rehabil N Am. 2000;11:881-894.
Sevick MA, Bradham DD, Muender M, et al. Cost-effectiveness of aerobic and resistance exercise in seniors with knee osteoarthritis. Med Sci Sports Exerc. 2000;32:1534-1540.
Felson DT. Nonmedicinal therapies for osteoarthritis. Bull Rheum Dis. 1998;27:5-7.
Mangione KK, McCully K, Gloviak A, Lefebvre I, Hofmann M, Craik R. The effects of high-intensity and low-intensity cycle ergometry in older adults with knee osteoarthritis. J Gerontol A Biol Sci Med Sci. 1999;54(4):M184-M190.
Hurley MV, Scott DL. Improvements in quadriceps sensorimotor function and disability of patients with knee osteoarthritis following a clinically practicable exercise regime. Br J Rheumatol. 1998;37:1181-1187.

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April 2003