Aquatic Therapy for the Arthritic Knee

34  Aquatic Therapy for the Arthritic Knee Lori Thein Brody

OUTLINE Introduction, 956 Scientific Foundation, 956 Aqua Physics, 957 Buoyancy, 957 Hydrostatic Pressure, 957 Viscosity and Hydrodynamics: Using Speed and Surface   Area, 958 Clinical Research, 959 Applications, 959 Mobility, 959 Muscle Performance, 961

Exercise Using Buoyancy, 961 Exercise Using Viscosity, 962 Balance, Stabilization, and Gait, 963 Cardiopulmonary, 964 Transition to Land, 967 Summary, 967

INTRODUCTION

ties, or other limitations. These patients often do well in an unweighted environment where they are able to perform full range of exercises directed at improved function.44 Preferably, exercises are not confined to a single environment but represent a comprehensive program of both land-based and water-based rehabilitation. It is not suggested that aquatic rehabilitation results in superior outcomes compared with land-based rehabilitation. Rather, the pool provides an effective, safe alternative for those who cannot tolerate a comprehensive rehabilitation program on land. The purpose of this chapter is to discuss the scientific basis for rehabilitative exercise in the water, and then apply this information to the treatment of patients with knee arthritis. Understanding the physical properties of water is critical for building a successful rehabilitation program in water. This understanding is both cognitive and kinesthetic. The reader is encouraged to experiment with these properties to fully understand how the body responds differently to exercises in water compared with land.

Water has been used for healing, spiritual, and religious purposes since at least 2400 bc.17 Water was used by the people of Asia to combat fevers as early as 1500 bc. Hippocrates (460-375 BC) used water for relief of muscle spasms and joint pain.25 For many years, water exercise was dismissed as a medical intervention and considered to be purely recreational. The advent of spas in Europe and around the world moved water-based interventions into the leisure and recreation category, making reimbursement for water-based medical interventions difficult. Despite a history spanning over 4000 years, a resurgence of aquatics as an intervention has occurred in the past quarter century. Throughout this history, many different terms have been used to describe rehabilitation that takes place in water. Some of these terms include hydrotherapy, aquatic therapy, spa therapy, water therapy, water gymnastics, balneotherapy and pool therapy. The term balneotherapy is distinguished from other forms of hydrotherapy. Balneotherapy refers to the use of hot-water or thermal treatments to decrease pain and stiffness and promote muscle relaxation. Balneotherapy often uses minerals, salts, or sulfur treatments, mud packs, and water jets to achieve these goals. Hydrotherapy is a general term covering any type of water intervention, which might include balneotherapy or exercise. For the purposes of this chapter, the focus remains on the use of exercise in water for the treatment of knee arthritis. For further information on balneotherapy, the reader is referred to Verhagen and coworkers.45 Physical therapy for patients with knee arthritis focuses on decreasing pain while improving mobility, muscle performance, motor control, and function. This is often achieved through stretching, strengthening, and balance exercises. However, many patients are unable to perform these exercises on land owing to pain, comorbidi-

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SCIENTIFIC FOUNDATION The scientific foundation for aquatic rehabilitation in patients with arthritic knees is found in two major areas. The first is the basis in aqua physics in which two key forces are critical for treatment planning. The first force is that of buoyancy. Buoyancy is used to unweight an arthritic extremity, normalize gait, and increase pain-free exercise. Buoyancy can also be used as resistance depending on equipment choices and patient positioning. The second force is that of viscosity. Viscosity is used to provide resistance for strengthening muscles from the core to the foot and to provide postural challenges that improve balance. The second major scientific foundational area is that of clinical research in which aquatic rehabilitation has been shown to increase measures of physical performance and to improve patient outcomes.

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CRITICAL POINTS  Scientific Basis • Buoyancy can unweight an arthritic joint while permitting rehabilitation activities to continue. • The precise amount of weight bearing at any given depth is unknown and is related to the individual’s body composition and speed of movement. • Buoyancy can assist, support, or resist a movement depending on how the individual is oriented in the water. • Viscosity can always override buoyancy as resistance if the surface area and speed are great enough. • Hydrostatic pressure can minimize swelling and edema in the lower limb that can occur with land-based exercise. • Hydrostatic pressure causes a centralization of peripheral blood flow with subsequent changes in the pulmonary and heart blood volumes. • Heart rates for exercise while immersed to the neck will be approximately 20 beats/min lower than comparable land-based exercise owing to hydrostatic pressure. FIG 34-1  Standing hip extension from 0 to 15 degrees of extension.

Aqua Physics The principles supporting the use of water in rehabilitation are based in physics. Several physical properties of water are key to understanding how water is a useful exercise mode for people with arthritis of the knee. Capitalizing on these properties can increase the opportunity for a successful outcome for these patients with complicated problems. Failure to recognize or understand how these principles work in harmony or in opposition can lead to poor outcomes. The key properties include buoyancy, hydrostatic pressure, and viscosity.

Buoyancy Buoyancy is the upward thrust experienced during immersion that is in direct opposition to gravity. Buoyancy is used to unload the lower extremity from the effects of gravity, making it a useful tool for those with knee arthritis. Archimedes’ principle states that an immersed body, at rest, experiences an upward thrust equal to the weight of the same fluid volume it displaces.6 Buoyancy is related to a person’s specific gravity (SG), which varies with body composition. Any object with an SG of less than 1.0 g/cm2 will float, whereas any object with an SG greater than 1.0 g/cm2 will sink. This property forms the basis of underwater weighing to determine body composition. Because lean body mass is heavier than fat mass, those with high lean body mass tend to sink, and those with greater fat mass float. This fact makes it difficult to know precisely how much weight bearing any given individual is achieving at a given water depth. Harrison and Bulstrode22 performed studies on percentage weight bearing during static standing in various water depths ranging from the hips to the neck. The authors found considerable variability in the amount of weight bearing with immersion at various depths. This variation might have been partly caused by using a fixed-depth pool and only nine subjects. However, the disparity may also be the result of differences in body composition and body fat distribution among individual study subjects, suggesting that weight-bearing prescription is difficult in this medium. A follow-up study by Harrison and associates23 showed that compared with static standing, fast walking increased weight-bearing forces up to 76%. Understanding Archimedes’ principle highlights the difficulties in assigning a specific percentage of weight bearing at any given depth; the weight on the limb will vary with body composition and speed of movement. The moment of buoyancy is also important in exercise prescription. As with moments of gravity on land, the moment of buoyancy increases with increasing lever arm length and nearer the parallel. If the

This is a buoyancy-assisted exercise with a short moment arm, making it a less effective exercise for gluteal muscle strengthening.

movement is in an upward direction, the same direction as the force of buoyancy, the activity is considered to be buoyancy assisted. If the movement in toward the pool bottom in opposition to buoyancy, it is considered to be buoyancy resisted. Movements parallel to the bottom that are neither assisted nor resisted by buoyancy are considered buoyancy-supported exercises. For example, in a standing position, a straight-leg lift forward would be assisted by buoyancy, whereas the return motion back to the neutral position would be buoyancy resisted. In a supine position, hip abduction and adduction would be buoyancysupported activities. An important application of this information is strengthening hip extensor muscles. In a standing position, the motion of hip extension from neutral to 15 degrees extension (the normal range of hip extension) occurs through such a small range of motion (ROM), with a short moment arm, and is buoyancy assisted, making the exercise a little more than a gluteal isometric exercise (Fig. 34-1). However, the motion from 90 degrees of hip flexion returning to neutral is also hip extension but is now moving through a larger range with a longer moment arm against the upward force of buoyancy, making this an effective hip extensor muscle-strengthening exercise (Fig. 34-2).

Hydrostatic Pressure Pascal’s law states that a fluid exerts pressure equally on an object at a given depth.6 Hydrostatic pressure increases with a greater depth of immersion owing to the weight of the volume of fluid overhead. The increased hydrostatic pressure close to the bottom of the pool assists venous return to the heart and prevents fluid accumulation in the lower extremities. This is useful for people with knee or ankle arthritis, who tend to experience swelling with exercise. The increased venous return to the heart also affects the cardiorespiratory system. The hydrostatic pressure when the body is immersed to the neck produces an increase in heart volume, intrapulmonary blood volume, right atrial pressure, left ventricular end-diastolic volume, stroke volume, and cardiac output.1,11 Heart rate is unchanged or decreased compared with similar land-based activities.1 Peripheral circulation and vital capacity are decreased.11 This cardiopulmonary response is significant for people with cardiorespiratory conditions and for those who are trying to achieve training heart rates in deep-water exercise.21 These changes have been noted in people both with and without cardiac disease.12,13 Aerobic exercise in neck-deep water will result in heart rates that are

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FIG 34-2  Hip extension from 90 degrees of flexion to neutral is a

FIG 34-3  Note the area of high pressure anteriorly and the area of low

buoyancy-resisted exercise with a longer moment arm, making it a more effective gluteal muscle-strengthening exercise.

pressure evidenced by eddies formed in the wake.

approximately 17 to 20 beats/min lower than comparable land-based exercise.2,20,38,42

Viscosity and Hydrodynamics: Using Speed and Surface Area The viscosity of a fluid is its resistance to adjacent fluid layers sliding freely by one another.6 Viscosity causes a resistance to flow when a body is moving through the water. As such, viscosity is clinically insignificant when a body is stationary. The viscous quality of water allows it to be used effectively for resistance because of its hydrodynamic properties, or fluid mechanics. The key hydrodynamic properties are turbulence and drag.40 Turbulent flow occurs when the speed of movement of an object (or person or body part) reaches a critical velocity or when the flow of water encounters an object (or person or body part).3 In turbulent flow, resistance is proportional to the velocity squared, and increasing the speed of movement significantly increases the resistance.32 Eddies are formed in the wake behind the moving body, creating drag that is greater in the unstreamlined object than in a streamlined object (Fig. 34-3). When moving through the water, the body experiences a frontal resistance proportional to the presenting surface area. Resistance can be increased by enlarging the surface area (Fig. 34-4). For example, walking forward or backward will produce greater drag in most people than walking sideways because of the greater surface area. Increasing the surface area or otherwise increasing drag increases the resistance to movement. The clinician has two variables to alter resistance produced by viscosity: the velocity of movement and the surface area or streamlined nature of the object. Several areas of research provide evidence for examining the impact of surface area and speed on force production. Law and Smidt27 used Hydrotone bells (Hydro-Tone Fitness Systems, Inc.) at different speeds and angles to assess the impact on force production. Results showed a 50% increase in force production at fast speeds. Force also increased at fast speeds when the bells were oriented at 45 degrees compared with 0 degrees. Orientation had no impact on force production when performed at slow speeds. Therefore both speed and surface area influence force production when using viscosity. Similar increases in drag were noted when using the Hydrotone boots compared with a barefoot condition.33 In a series of studies, Poyhonen and coworkers32-34 found that increasing the surface area of

FIG 34-4  Adding the plow increases the surface area and creates additional drag.

the lower leg significantly increased the level of water resistance. Interestingly, electromyographic (EMG) activity of the knee flexors and extensors was similar between barefoot and increased surface area conditions despite the increased drag caused by the boot. This EMG finding was the result of self-selected speed changes by the subjects. Speed was uncontrolled in the study, and subjects performed the exercise faster in the barefoot condition. This reinforces how similar muscle activation can be obtained by manipulating speed and/or surface area when using viscosity as the primary resistance. Both strategies will overload the muscle, allowing the exercise prescription to be specific to each patient’s needs. Electromyographic data has also been used to examine the relationship between muscle activation and speed in the shoulder musculature. Data from the deltoid and rotator cuff musculature were captured during arm elevation at three different speeds (30, 45, and 90 degrees/ sec) on land and in the water.26 The percent maximum voluntary contraction was consistently higher on land at the two slowest speeds but higher in the water at 90 degrees/sec, highlighting the positive relationship among viscosity, speed, and force generation.

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Research in the cardiopulmonary effects of speed on exertion measures also supports the positive relationship between speed and work in the water. Whitley and Schoene47 examined walking on land and in the water at four different speeds. Heart rates were significantly higher after water-walking versus treadmill walking at all four speeds. In  addition, heart rates rose significantly with each increasing speed in water-walking, suggesting increasing cardiopulmonary workloads at increasing speeds. Cassady and Nielsen10 measured oxygen consumption during calisthenic arm and leg exercises at three different speeds on land and in the water. They also found increasing heart rate with increasing speed of exercise in the water. The higher metabolic cost of exercises at a faster speed supports the theory of increased work at faster speeds in the water.

A group of 312 patients with hip or knee osteoarthritis was randomized into control and water exercise groups. The control group received usual care, and the intervention group received aquatic exercise for 1 year with follow-up for an additional 6 months. Results showed a favorable cost/benefit ratio as measured by a reduction in WOMAC pain as the measure of benefit. Structured aquatic physical therapy for patients with knee arthritis is gaining momentum, with evidence supporting the clinical and costeffectiveness of this intervention in this population. Outcomes following aquatic physical therapy appear to be similar to land-based rehabilitation, making the pool a viable alternative for those who are unable to rehabilitate on land or who have a preference for aquatic based exercise.4,5,16,35

CLINICAL RESEARCH

APPLICATIONS

Clinical research has supported the effectiveness of aquatic rehabilitation for persons with knee arthritis. A study examining outcomes following a water-based program for patients with lower limb osteoarthritis found that group-based water exercise classes over 1 year produced significant reductions in pain and improvements in function.14 A randomized, controlled trial (RCT) compared the effects of a water-based resistance program with a land-based program on function and strength in patients with osteoarthritis of the hip or knee.18 The authors found improvements in strength and function in both the land- and the water-based groups as compared with the control group. Compliance rates were 84% for water therapy and 75% for land therapy. In a similar study, Wyatt and coworkers48 examined change in function following a land-based or an aquatic exercise program in patients with knee osteoarthritis. Both groups showed significant improvements in measures of ROM, thigh girth, pain scales, and 1-mile walk test. However, the aquatic group had significantly lower pain levels than the land group. These results reinforce that patients can improve strength and function effectively in either a land or aquatic environment.48,39 The key is the ability to provide a comprehensive and sustainable program, whether on land, in the water, or some combination of both. Ongoing exercise at the conclusion of formal rehabilitation is essential to prevent symptom recurrences. Addressing the issue of compliance with a rehabilitation program, Hinman and colleagues24 performed an RCT randomly assigned 71 participants with hip or knee osteoarthritis to 6 weeks of aquatic physical therapy or no physical therapy. Patients in the aquatic physical therapy program had less pain and joint stiffness and greater physical function, quality of life, and hip muscle strength than the control group. Nearly 75% of participants reported improvements in pain and function compared with 17% in the control group. More important, 84% of participants continued the aquatic program independently at the conclusion of the study. The chronic nature of osteoarthritis requires ongoing participation in an exercise program at the conclusion of formal rehabilitation.7 Although the previous study compared aquatic physical therapy with no physical therapy, Fransen and coworkers19 compared hydrotherapy with ai chi or a control group in an RCT of 152 patients with hip or knee osteoarthritis. Results showed that both hydrotherapy and ai chi participants improved in the pain and physical function subscales of the Western Ontario and McMaster Osteoarthritis Index (WOMAC), but only the hydrotherapy group achieved significant improvements in the physical performance measures of the ShortForm-12 item questionnaire (SF-12). In addition, compliance with the hydrotherapy classes was higher than compliance with ai chi. Pools are expensive to maintain and operate. An RCT examined the cost-effectiveness of water-based therapy for lower limb osteoarthritis.

Although patients with knee arthritis have individualized problems and differing comorbidities, some generalizations about preferred applications in this population can be made based on the pathology and commonly associated limitations. A thorough examination is the foundation for determining the appropriate exercise intervention. Awareness of the interrelationships among lower extremity joints and the spine can ensure proper positioning and targeting of the tissue of interest. Altering the position of the hip or foot can significantly affect the loads across the knee. The following discussion is meant to provide examples of how the physical properties of water can be exploited to improve function in patients with knee osteoarthritis.

Mobility Many activities typically performed on land can be modified, adapted, and used in the pool. Mobility has both a static component and dynamic. Functional mobility requires both appropriate soft tissue extensibility, achieved through stretching exercises, and dynamic mobility, achieved through a combination of stretching, strengthening, balance, and neuromuscular retraining. Soft tissue stretching exercises are readily and easily performed in the pool. Many patients with arthritis have difficulty stretching on land owing to the positions or postures required. For example, some individuals are unable to get up and down off the floor or lack a sufficient supportive surface to perform the exercises appropriately. Some stretches require bending, twisting, reaching, or have weight-bearing components that patients are unable to accomplish on land. For

CRITICAL POINTS  Applications • Stretching is readily performed in the pool because positioning is simple and gravity is minimized. • Stretching can be performed in functional upright positions using buoyant equipment or stationary features of the pool. • Static stretching should be combined with dynamic mobility exercises for functional mobility. • Buoyancy, viscosity, or the water’s hydrodynamic principles can be used for improving muscle performance. • Rapid direction changes can be used to challenge buoyancy and elicit eccentric muscle contractions. • A variety of arm and trunk movements can be used to challenge dynamic balance. • The water- and land-based programs can be progressed in tandem, with an eye to the long-term medium that will best support a lifetime of exercise.

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example, hamstring or quadriceps muscle stretches often require balancing on a single leg or getting up and down off the floor. Many of these exercises are easily performed in the pool with stationary or buoyant equipment. The water’s warmth and support from buoyancy make it easier and more relaxing to achieve a successful stretch. As on land, muscles crossing both the hip and knee or both the knee and ankle are stretched together. Thus the position of the adjacent joint becomes important. Because many of the stretches use buoyancy, it is easy to adjust the stretch to decrease stress on the joints and emphasize the soft tissue component. Key muscles to be stretched in patients with knee arthritis include the gastrocnemius and soleus muscles as well as the quadriceps, hamstring, lateral hip (iliotibial band), and gluteal/buttock muscles (Figs. 34-5 to 34-7). As with stretching exercises on land, the intensity should be subjectively between “low” and “medium” and should be pain free. The patient should feel stretching in the muscle of interest and not in the joint itself. The patient should be able to hold the stretch for 60 seconds without an increase in pain.3 Repeat the stretches for two to three repetitions.

FIG 34-5  Hamstring stretching using a noodle. Other stationary equipment in the pool can also be used for stretching.

FIG 34-6  Lateral hip stretching. Start in the hamstring stretch position, then horizontally adduct approximately 15 degrees and internally rotate.

Dynamic mobility is easily accomplished in the pool. Dynamic mobility has been advocated as an appropriate means to increase functional mobility because it requires not only static flexibility but also strength, balance, and neuromotor coordination.29 Dynamic mobility activities in the pool take place in a gravity-lessened environment, which decreases joint-loading forces. The water’s viscosity also slows movement and increases the reaction time for patients with balance difficulties. This property makes the pool a safe environment for such individuals. Dynamic mobility activities can easily replicate similar activities performed on land. Walking forward with varying speed and step length can be modified to emphasize lower extremity mobility. Cue the patient for increased knee flexion and extension during the swing phase of gait. Ankle or hip mobility can be similarly cued to increase sagittal plane mobility. Backward walking is useful for increasing dynamic knee flexion because increased knee flexion is required to clear the ground during walking this direction. Frontal plane mobility is emphasized by walking sideways. Other dynamic mobility activities include marching in place and marching across the pool. Vary the amount of hip and knee flexion based on the patient’s needs. Marching does not need to proceed in a straight line but can be on a diagonal to encourage more functional movement patterns. Proprioceptive neuromuscular facilitation (PNF) patterns also encourage functional movement patterns in the lower extremity. Cueing the patient appropriately can emphasize motion at the knee joint when tolerated. For closed-chain dynamic mobility, perform squats for hip, knee, and ankle mobility in shallow water or fully flex the hips and knees by flexing and extending these joints at a ladder (Fig. 34-8). These closed-chain activities can be progressed by asking the patient to lunge during ambulation. Dynamic mobility of other joints in the kinetic chain such as the hip and low back is necessary to accommodate potential motion losses at the knee. Motions out of the straight plane such as figure-of-eights or other movement patterns can enhance mobility at these joints. Ai chi exercise stresses balance, stability, and mobility throughout the kinetic chain (Figs. 34-9 and 34-10). Dynamic mobility can also be performed non–weight bearing. Bicycling or running with a belt or a noodle is a good way to perform repeated hip and knee flexion and extension. The range of movement can be modified as needed for any given patient. Similarly, deep-water

FIG 34-7  Quadriceps muscle stretching with a noodle.

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cross-country skiing requires repeated non–weight-bearing sagittal plane mobility, with greater hip motion and less knee motion. These repeated movements provide lubrication via mobility, but lack the weight-bearing component necessary for articular cartilage lubrication (Table 34-1).46

Muscle Performance

FIG 34-8  Knee-to-chest stretching on a ladder.

Clinicians can use buoyancy, viscosity, or hydrodynamics as tools to increase lower extremity and core strength in individuals with arthritis. A variety of activities using all components will produce a wellrounded rehabilitation program. The starting point is established during the patient’s examination when the strength of surrounding muscles and the irritability of the joint are determined. For example, in a patient with an irritable knee and decreased strength, buoyancy might be used to assist the exercise, whereas in a patient with a less irritable joint and greater strength, buoyancy may be used as resistance. Whether using buoyancy or viscosity, exercises can be performed in an open chain, a closed chain, or some combination of both.

Exercise Using Buoyancy

FIG 34-9  Ai chi balancing pattern of hip extension with bilateral shoulder flexion.

FIG 34-10  Ai chi balancing pattern of hip flexion with bilateral shoulder extension.

For patients needing buoyancy assistance, squats, step-ups, or stepdowns in deeper water will provide the necessary assistance in both the eccentric and concentric phases of the exercise. Specially designed boxes can be submerged in water of any depth to find the appropriate amount of assistance/resistance for a given patient. A box submerged in 4 to 4.5 feet of water is a good place to start for the average adult. Remember that the amount of assistance provided by buoyancy will vary with body type. Thus the exercise prescription must be specific to the individual. As the patient improves, progress the buoyancy-assisted exercises by moving the exercise to more shallow water. This will increase the forces of gravity and lessen the assistance by buoyancy. Exercises can also be progressed to positions such as the lunge position, which is more challenging. Lunges can be performed in place or moving forward (Fig. 34-11), backward, or sideways. Strengthening exercises can also use buoyancy as resistance. Adding buoyant equipment to the foot or ankle will increase the challenge of these exercises. Straight-leg lifts in the sagittal or frontal planes will result in concentric and eccentric contractions of the muscle groups positioned in opposition to buoyancy. For example, lifting the leg forward and back down will result in eccentric and concentric contractions of the hip extensor muscles if sufficient buoyant equipment is used. If the amount of buoyant equipment is inadequate or the speed not high enough, the muscle contractions become alternating concentric contractions of the hip flexor muscles and hip extensor muscles. Therefore the relative amounts of muscle strength and buoyant equipment will determine which muscle groups are working and in what type of muscle contraction. These straight-leg lifts strengthen the core hip muscles isotonically while challenging the muscles at the knee isometrically. To challenge these muscles directly, perform buoyancyresisted hamstring curls in a standing position with the hip flexed to 90 degrees (Fig. 34-12). Buoyancy-resisted quadriceps exercises are performed in a standing position with the knee moving from extension to flexion (Fig. 34-13). Realize that while the moving limb is working in an open chain, the opposite limb is working in a closed chain to stabilize the body against the hydrodynamic forces created by the moving limb. This principle is one of the strengths of working in the aquatic medium. Functional movement patterns can be trained using buoyant equipment. The same PNF patterns used for mobility can be used for strengthening using buoyant equipment. For example, place a Wet Vest strap (Hydro-Fit, Inc.) around the ankle and perform PNF diagonals, alphabet writing, or other functional movement patterns with the leg

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TABLE 34-1  Exercises for Mobility Level 1 Exercise

Level 2 Exercise

Level 3 Exercise

Additional Challenge

Passive knee extension with noodle under midcalf Passive knee flexion with noodle under midshin March in place

Noodle under ankle

Foot on rigid object

Provide downward pressure on knee

Noodle under ankle

Foot on rigid object

Provide overpressure into flexion

March across pool

Add stop to provide additional balance challenge

Standing knee flexion/ extension with support Bicycle in stable, supported position Squats at railing

Increase range of motion

Emphasize gait components such as knee flexion or extension, vary step length Add buoyant equipment

Bicycle on noodle or with vest

Increase range of motion, speed

Increase depth of squat

Stationary lunges Hip mobility through single plane with support

Increase stride length Hip flexion/extension, abduction/ adduction, figure-eights

Progress to hip and knee flexion on ladder Increase depth of lunge Increase range of motion, remove support

Vary activity to emphasize flexion or extension or both Bring knees closer to chest as tolerated Progress to forward-moving lunges Add carioca walking, walking with direction changes and varying step length

Remove support

Progress exercises from one level to the next after successful completion of the previous level.

FIG 34-11  Lunge walking.

FIG

34-13  Standing

quadriceps

strengthening

with

buoyant

equipment.

straight. This type of movement provides resistive exercise to muscles throughout the entire leg. Place a noodle under the bottom of a foot and press down as in a leg press for a buoyancy-resisted leg press activity (Fig. 34-14). Exercises using buoyancy as the primary resistance are increased by adding more buoyancy, as in adding more weight on land.

Exercise Using Viscosity

FIG 34-12  Hamstring curls with buoyant equipment.

Open- or closed-chain exercises using viscosity provide an opportunity to strengthen lower extremity muscles isotonically. It is important to consider how the exercises are performed to ensure that the structures of interest are being challenged. Exercises using viscosity as the primary resistance are increased by increasing the exercise speed, the surface area, or both. A study of the hydrodynamic responses to viscosityresisted single and repeated knee flexion and extension in water found high levels of antagonist activity with the repeated activity and lower levels with the single repetition activity.34 This is an important issue for those wanting to provide both concentric and eccentric muscle

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walking forward while simultaneously horizontally adducting the shoulders. Be aware of the additional stress this will place on the shoulders (Table 34-2). Finally, resistance bands typically used on land can be applied in the water. Resistive hip, knee, and ankle exercises, as well as resistive walking patterns, can be successful in water because of the resistance applied to the musculature without the weigh-bearing effects of gravity (Fig. 34-17).

Balance, Stabilization, and Gait

FIG 34-14  Buoyancy-resisted leg press performed with a noodle.

contractions during aquatic rehabilitation. Although concentric and eccentric contractions of a single muscle group can be achieved using buoyancy-resisted exercise (such as standing knee extension with buoyant equipment, Fig. 34-15, A and B), this same exercise using viscosity (such as standing knee extension with a resistive fin) produces reciprocal concentric contractions (see Fig. 34-15, C and D). However, research by Poyhonen and associates33 suggested that the muscle activity is influenced by the surface area, speed, and limb orientation. During both the flexion and extension phases of a knee flexion and extension activity in water, the agonist EMG activity decreased with a concurrent increase in the antagonist EMG during the final portion of ROM. This finding suggests that the moment of the moving water produces lift that tends to “carry” the limb through the final ROM, requiring antagonist activation to decelerate the limb at end ROM. This is more evident in extension phase of seated knee extension than in the knee flexion phase owing to the additional lift from buoyancy. Therefore the quadriceps muscles will be activated through a greater ROM if performed in standing and the hip in neutral than in a seated or standing position with the hip at 90 degrees. Similarly, if the goal is to facilitate hamstring muscle activation and minimize quadriceps muscle activation near full knee extension (as in anterior cruciate ligament injuries), then the 90 degrees of hip flexion position would be preferable (Fig. 34-16). Progress activities using viscosity as resistance by increasing the speed and/or surface area of the exercise. Flippers or fins are good choices for increasing the surface area. Flippers tend to work best in the sagittal plane, whereas Aquafins (Hygenic Corporation) can be placed in any plane, providing resistance in the sagittal plane, frontal plane, or on any diagonal in between. Other resistive equipment, such as a Hydro Boot (Hydro-Tone Fitness Systems, Inc.), provides a larger surface area for greater resistance.34 Leg kicks, knee exercises, or walking activities can be performed with resistive fins around the ankle. Different components of the activity can be emphasized depending on how the exercise is cued. For example, during backward walking, emphasizing the knee flexion component will challenge the hamstring and gastrocnemius muscles whereas stressing the hip extension component will challenge the hamstring and gluteal muscles. Generate more resistance by positioning the arms with increased surface area. For example, walk forward with the arms held at 90 degrees abduction or increase the challenge by

The hydrodynamic forces of water provide excellent opportunities for activities to challenge the core muscles and balance. A study of balance training on land and in water found both mediums resulted in improvements in the center of pressure variables,37 although outcomes research looking at the 8-foot up-and-go test found greater improvement in an aquatic-exercise group compared with a land-exercise group.8 An 8-week program of aquatic exercise in older adults demonstrated improvements in measures of gait stability.28 Exercise training on an aquatic treadmill led to improvements in joint angular velocity and pain in patients with knee osteoarthritis.36 Exercises can be stationary or moving and can be challenged in a variety of ways. Although strength is important, it is only one component of a program to enhance balance. Muscle activation patterns and knowledge of position in space also contribute to good balance. Patients can use their arms to create forces that are resisted by their trunk and core muscles. Reciprocal shoulder flexion and extension produce rotational forces that are resisted by the core muscles. Turning the palms to the direction of movement increases surface area and increases the challenge. Likewise, symmetrical, bilateral shoulder internal and external rotation also creates rotational forces resisted by the trunk. Anterior-posterior sway is produced with any bilateral anteriorposterior movement of the arms such as flexion/extension or horizontal abduction/adduction. Increase the challenge of these exercises by increasing the exercise speed or surface area or by decreasing the base of support by bringing the feet closer together. Further increase the challenge by removing the bilateral symmetry. For example, performing shoulder horizontal abduction/adduction with a single arm  minimizes the anterior-posterior sway and produces trunk rotation (Fig. 34-18). Progress the narrow base of support to exercise on a single foot as appropriate. Rotational activities will be difficult on a single foot and may not be appropriate for all patients with complex knee problems. Other sagittal or frontal plane activities may be appropriate on a  single leg and challenge balance. Simple hip flexion/extension or hip abduction/adduction on a single leg will challenge balance if no external support is provided. For people with chronic knee problems,  continuous standing for several repetitions on a single leg may be inappropriate. Consider alternating legs every repetition or every few repetitions for these patients. Other dynamic activities can capitalize on the physical properties of water. Continuous moving in one direction is not particularly challenging to the core muscles other than the generalized strengthening that occurs with walking against resistance. Once an individual begins moving through the water, the momentum of the water produces lift, carrying the body along through the water. The real challenge to balance and strength occurs with stopping and changing direction once this momentum is achieved. A beginning activity is simply stepping forward onto one foot and balancing followed by a step backwards and balancing again. Increase the challenge by taking three or four steps forward, stop and balance, followed by three or four steps backwards, stop and balance. A few steps one direction is enough to get the water moving along with the patient. Stopping and balancing,

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A

B

C

D

FIG 34-15  A and B, Standing knee extension using buoyant equipment with the hip in neutral results in eccentric and concentric quadriceps muscle contractions. C and D, Standing knee extension and flexion using surface area-increasing equipment results in reciprocal concentric quadriceps and hamstring muscle activation. The hip position does not change this activation pattern.

then changing direction produces significant balance challenges. This same pattern can be repeated moving in different directions. Further increase the challenge of the activity by increasing the speed of walking, decreasing arm assistance by placing the arms across the chest and/or decreasing visual input by closing the eyes. Finally, tip or turn the head to include the vestibular component. Other balance exercises use movements of the arms or opposite leg while stabilizing on a single leg. A stepping motion with a concurrent pushing and pulling motion with resistive equipment makes an excellent core strengthening and balance exercise. In single-leg stance,

pushing a ball down works on stability of the entire lower extremity. To increase the challenge, these exercises can be performed on an unstable base such as Therafoam (Hygenic Corporation) submerged in the water (Table 34-3).

Cardiopulmonary Regular aerobic exercise is an important component of general fitness and weight loss. The American College of Sports Medicine41 and the American Heart Association recommend performing moderately intense cardiopulmonary activity 30 minutes a day, 5 days a week, or

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FIG 34-16  Standing knee flexion and extension with the hip at 90 degrees of flexion facilitates hamstring activation near full extension because these muscle work to decelerate the extending knee.

FIG 34-17  Monster walks with resistive band around ankles. The band can also be placed above the knees for less resistance across the knee joint.

TABLE 34-2  Aquatic Strengthening Activities Level 1 Exercise

Level 2 Exercise

Level 3 Exercise

Level 4 Exercise

Comments

Standing hip flexion/ extension

Add fins or buoyant equipment

Increase speed in a controlled fashion

Standing hip abduction/ adduction

Add fins or buoyant equipment

Increase speed in a controlled fashion

Progress to unsupported will further challenge balance Progress to unsupported will further challenge balance

Standing knee flexion/extension

Add fins or buoyant equipment

Increase speed in a controlled fashion

Progress to unsupported will further challenge balance

Buoyant equipment will emphasize hip extensors; fins will equally emphasize flexors and extensors Buoyant equipment will emphasize hip adductors; fins will equally emphasize adductors and abductors Buoyant equipment will emphasize knee flexors with hip at 90 degrees, extensors with hip in neutral; fins will equally emphasize flexors and extensors

Wall-sits

Progress to single leg

Squats with arm support Lunge

Progress to single leg

Add arm and/or contralateral leg movement to perturb Bilateral squat without support

Decrease depth to increase weight bearing Decrease depth to increase weight bearing Lunge walk across pool

Noodle depression activities Stepping activities Resistive band exercises Deep-water activities

Stationary lunge with support Noodle leg press with foot kept close, more knee flexion Step-ups on box Walking with band at knees Bicycling, cross country skiing, running, vertical or supine kicking

Stationary lunge without support Noodle figure-of-eights or alphabet writing; foot further away, knee more extended Decrease depth to increase weight bearing Walking with band at ankles Add fins

Progress to higher levels upon successful completion of prior levels.

Increase depth and/or buoyancy to increase resistance Perform in a variety of directions Standing single leg activities with support Increase speed or add interval training

Can add toe-raise to increase calf muscle work Can be performed in any direction Remove support to add balance challenge Decrease depth to increase challenge Standing single leg activities without support

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A

B FIG 34-18  Balance exercise that performs shoulder horizontal abduction and adduction bilaterally. A, This position creates anterior-posterior sway. B, Single-arm position creates transverse plane rotation.

TABLE 34-3  Aquatic Balance Activities Level 1 Exercise

Level 2 Exercise

Level 3 Exercise

Level 4 Exercise

Comments

Bilateral shoulder flexion/extension

Narrow base of support

Single foot

On unstable surface, such as immersible foam

Bilateral horizontal abduction/adduction

Narrow base of support

Single foot

On unstable surface, such as immersible foam

Reciprocal shoulder internal/external rotation Stepping exercises

Narrow base of support

Single foot

Step and hold forward and backward, with then without, arm balance Hip flexion/extension, abduction/adduction Hop forward/back, side-to-side

Three-step stop, with then without, arm balance Standing knee flexion/extension Hop on diagonal

On unstable surface, such as immersible foam Stepping push-pull with resistive equipment Arms across chest

Close eyes, add head movement to increase balance challenge; can also add gloves to increase resistance, or to single arm to emphasize core Close eyes, add head movement to increase balance challenge; can also add gloves to increase resistance, or to single arm to emphasize core Close eyes, add head movement to increase balance challenge; can also add gloves to increase resistance Close eyes, increase speed; perform in any direction

Single-leg activities, unsupported Hop in place, with stable balance in between

Arms across chest, close eyes

Close eyes, add unstable surface Perform 2-2, 2-1, 1-2, 1-1 footed with emphasis on stability upon landing

Progress to higher levels upon successful completion of the previous level.

performing vigorously intense cardiopulmonary activity 20 minutes a day, 3 days a week. These organizations also recommend regular strength-training exercises. For people with arthritis or complex problems at the knee, many of the traditional cardiopulmonary training activities are too painful. Most of these activities involve some weight bearing through the knee. Walking, running, elliptical trainers, stair steppers, and ski machines all require weight bearing through the knee. Bicycling places less weight-bearing loads across the knee than other cardiopulmonary training activities, but still places large demands on this joint. The water is an excellent alternative to cardiopulmonary training on land. Patients do not need to be skilled swimmers to achieve a training effect in the pool. Alternative non-weight-bearing activities include deep-water bicycling, cross-country skiing or deep-water running. Vertical kicking or deep-water aerobics classes also provide a good training stimulus. For some individuals, walking in chest-deep water at a steady pace is sufficient cardiopulmonary training. One study found that walking backward in chest-deep water elicited greater

physiological and perceptual responses than walking forward at the same speed.30 Another investigation reported that muscle activity, cardiorespiratory responses, and rate of perceived exertion were all greater in elderly patients who walked in water compared with those who walked on land.31 For those who like to swim, traditional swim strokes can be modified to improve their efficiency. Adding a mask and snorkel decreases the amount of neck and trunk rotation necessary during the crawl stroke and the amount of extension necessary during breaststroke. This may increase the efficiency of the stroke and decrease stresses on the spine, allowing individuals to swim continuously enough to obtain the desired cardiopulmonary results. Adding flippers increases the torque production of the leg muscles and may decrease loads on the knees caused by inefficient kicking techniques. Simple flutter kicking with flippers is a good cardiopulmonary exercise. However, the frog or whip kick usually associated with breaststroke swimming places additional torque on the medial knee and may be painful for many people with knee arthritis.

CHAPTER 34  Aquatic Therapy for the Arthritic Knee Circuit training or interval-training techniques can also be incorporated into the cardiopulmonary program. Speed play is a simple technique to increase the musculoskeletal and cardiorespiratory demands of an activity. For example, when walking the length of the pool, begin at the usual pace, gradually build in speed to midway across the pool, and then gradually slow back to the usual pace by the time the other end of the pool is reached. This type of training can be incorporated into any of the cardiorespiratory activities, using time or repetitions as the metric for adjusting the speed. A circuit training strategy is often necessary for patients with osteoarthritis because any continuous repetitive activity can flare one or more arthritic joints. A combination program of lap swimming activities alternated with deep water running, cycling, vertical kicking, and/or cross-country skiing can provide a sufficiently varied cardiorespiratory workout without overstressing any single joint. Research has shown that subjects exercising in the water can achieve a sufficient training stimulus.9,15,43 D’Aquisto and colleagues15 and Campbell and coworkers9 found that controlling the frequency, intensity, and duration of shallow water exercise resulted in a training response sufficient to meet the American College of Sports Medicine’s guidelines in younger and older women. Takeshima and associates43 found that exercising three times per week for 12 weeks resulted in an increase in peak volume of oxygen consumption. Improvements in muscle strength, power, flexibility, agility, and subcutaneous fat were also found. All of these changes are positive for people who have complex knee problems. Training parameters in the water are basically the same as land. Manipulating the frequency, intensity, and duration to meet the American College of Sports Medicine’s guidelines follows the same thought process as those on land. One important issue is skill level in the water. Unskilled deep-water exercisers report higher rates of perceived exertion and have higher lactate levels than skilled deep-water runners. As patients become skilled and comfortable with the new techniques, the exertion levels and heart rate will decrease. Exercise in deep water will result in a heart rate approximately 20 beats/min lower than comparable land-based exercise because of the effects of hydrostatic pressure.42

TRANSITION TO LAND Transition to land-based activities should be a part of the patient’s treatment program. The balance between land-based and aquaticbased activities will vary from one patient to the next. Several issues must be considered when determining this balance. The patient’s tolerance for land-based activities is a key consideration. If the patient is unable to achieve a sufficient training stimulus on land because of pain, swelling, or other mechanical symptoms, then the majority of the rehabilitation and maintenance program will likely contain an aquatic component. This can be achieved through an independent rehabilitation and exercise program at a local pool, or a community aquatic exercise class. In contrast, some patients may not tolerate regular aquatic exercise caused by reactions to pool chemicals. These individuals may need more land-based activities or find an alternative pool with fewer chemicals such as a salt-water system pool. Other considerations are pool availability and the patient’s preferences. The transition to land occurs similarly to other transitions in rehabilitation. Frequently, patients begin with programs that are primarily in the water, with the addition of a few land-based exercises that they tolerate and can complement the water activities. As the patient tolerates this program and healing progresses, the land-based component is gradually increased and the aquatic component is maintained  or increased in parallel, as the patient tolerates. The long-term

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progression and outcome is dependent on the patient’s long-term goals and whether these are best met with an aquatic program, a land program, or some combination of both. The ultimate goal should be the design of a program that the patient can easily maintain because of its ease, effectiveness, and enjoyment. This requires a partnership and communication between the therapist and patient.

SUMMARY The water is an excellent exercise, training, and rehabilitation medium for patients with arthritis. The water’s buoyancy unweights painful joints, allowing greater ease of movement and the ability to train and strengthen without high joint compressive forces. The unweighting reduces pain and allows more active participation in the rehabilitation process. The hydrostatic pressure controls lower extremity swelling that may accompany exercise in people with arthritis. Finally, the water’s viscosity provides resistance for strengthening and support against falls caused by poor balance. Research into the efficacy of water-based exercise is ongoing. As with all interventions, exercise in the water is not for everyone. However, for those who tolerate or enjoy the water, this environment can provide opportunities to rehabilitate and exercise across the lifespan. More importantly, research has shown strong compliance with aquatic programs with continued participation at the conclusion of the structured program. For patients with knee osteoarthritis, ongoing, regular exercise, whether on land or water or both, is critical for preventing a progressive decline in function.

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