Hydrotherapy / Aquatic Therapy in Physiotherapy: Principles, Benefits, Indications, Contraindications and Evidence-Based Applications
Hydrotherapy, also called aquatic therapy or water-based therapy, uses the physical properties of water to assist rehabilitation, exercise, pain management, mobility training, strengthening, balance training and cardiovascular conditioning.
Unlike land-based exercise, aquatic therapy allows the physiotherapist to manipulate buoyancy, hydrostatic pressure, water resistance, turbulence, temperature and depth to change the mechanical demands placed on the body.
This makes the aquatic environment particularly useful when conventional land-based exercise is difficult because of pain, reduced weight-bearing tolerance, weakness, impaired balance or limited mobility.
However, aquatic therapy is not simply "exercise made easier." Water can reduce gravitational loading while simultaneously creating substantial resistance to movement and cardiovascular demands.
Current evidence supports aquatic exercise for several conditions, particularly osteoarthritis, chronic low back pain and some chronic pain conditions, while evidence for neurological rehabilitation is promising but varies in quality and clinical significance. (PubMed)
What Is Hydrotherapy / Aquatic Therapy?
Hydrotherapy is the therapeutic use of water for rehabilitation or treatment.
Aquatic therapy generally refers to structured therapeutic exercise or movement performed in water under the supervision of a physiotherapist or appropriately trained rehabilitation professional.
It can include:
Walking in water
Active range-of-motion exercises
Strengthening exercises
Balance training
Gait retraining
Aerobic conditioning
Functional movement practice
Stretching
Neuromuscular training
Sport-specific rehabilitation
Relaxation and mobility exercises
Aquatic therapy should be distinguished from recreational swimming.
A patient does not need to know how to swim to participate in many aquatic rehabilitation programs. Exercise may be performed in shallow or deeper water while using the pool wall, rail, flotation devices or therapist assistance.
The therapeutic effect comes from manipulating the physical properties of water rather than simply swimming laps.
Physics Behind Aquatic Therapy
The effectiveness of aquatic therapy is closely related to basic principles of fluid mechanics, hydrostatics, thermodynamics and biomechanics.
The major physical properties used clinically are:
Buoyancy
Hydrostatic pressure
Water density
Viscosity and drag
Turbulence
Water temperature
Thermal conductivity and specific heat
Changes in the relationship between the body's center of gravity and center of buoyancy
Understanding these principles helps the physiotherapist determine how difficult or easy an exercise will be.
1. Buoyancy
Buoyancy is one of the most important principles in aquatic rehabilitation.
According to Archimedes' principle, an immersed object experiences an upward force equal to the weight of the fluid displaced by that object.
In simple terms:
Water pushes upward against the body.
This reduces the effective load that the musculoskeletal system must support.
The deeper a person is immersed, the greater the proportion of body weight that is unloaded.
Therefore:
Deeper immersion → greater buoyancy support
Shallower immersion → greater weight-bearing demand
This provides a useful way to progressively load a patient.
For example, a patient with painful knee osteoarthritis may find walking easier when immersed to approximately chest or xiphoid level because water supports a significant portion of body weight.
As rehabilitation progresses, the therapist can move the patient into shallower water, increasing the weight-bearing requirement.
Buoyancy can therefore be used as a graded loading tool.
2. Hydrostatic Pressure
Hydrostatic pressure is the pressure exerted by a fluid at rest.
It can be expressed as:
P = ρgh
where:
P = hydrostatic pressure
ρ = density of water
g = gravitational acceleration
h = depth below the water surface
Pressure increases with depth.
Therefore, the feet experience greater hydrostatic pressure than the knees, and the knees experience greater pressure than the hips during upright immersion.
Hydrostatic pressure can:
Reduce peripheral fluid accumulation
Influence venous return
Provide uniform external pressure
Affect cardiovascular responses
Change respiratory mechanics
Immersion causes blood to shift toward the central circulation, increasing venous return and altering cardiac and respiratory physiology. (PubMed)
This is therapeutically useful in some patients but can also create important precautions in people with significant cardiopulmonary disease.
3. Viscosity and Water Resistance
Water provides resistance when the body moves through it.
Unlike gravity-dependent loading, resistance from water can be applied in multiple directions.
The faster a person moves through water, the greater the resistance generally becomes.
Therefore:
Slow movement → lower resistance
Fast movement → higher resistance
This allows the therapist to increase exercise intensity simply by changing movement speed.
Resistance can also be increased by:
Increasing the surface area of the moving limb
Using paddles
Using aquatic gloves
Using fins or resistance equipment
Creating turbulence
Changing movement direction
This makes water useful for strengthening without necessarily requiring heavy external weights.
4. Drag Force
When a body moves through water, it experiences drag.
A simplified relationship is:
Drag ∝ velocity²
This means that increasing movement speed can produce a disproportionately greater increase in water resistance.
For example, a patient may perform shoulder abduction slowly during early rehabilitation.
Later, the same movement can be made more challenging by increasing speed or adding equipment that increases surface area.
Thus, aquatic resistance can be progressively manipulated without changing the basic exercise.
5. Turbulence
Turbulence occurs when water flow becomes irregular.
A therapist can deliberately create turbulence by:
Moving the arms rapidly
Changing direction
Walking behind another person
Using resistance equipment
Creating waves in the water
Turbulence challenges:
Balance
Postural control
Core stability
Reactive responses
Neuromuscular coordination
This can be particularly useful during balance and gait rehabilitation.
However, turbulence should be introduced gradually in patients with significant balance impairment.
6. Center of Gravity and Center of Buoyancy
On land, the body's center of gravity is primarily influenced by body mass distribution.
In water, an additional force acts through the center of buoyancy, which is related to the volume of water displaced.
The interaction between these forces changes balance and body orientation.
This produces an interesting rehabilitation environment.
Water can simultaneously:
Support the body
Reduce fear of falling
Slow movements
Provide resistance
Challenge postural control
A patient may therefore practice balance strategies in a relatively controlled environment before progressing to more demanding land-based tasks.
7. Thermal Properties of Water
Water has a high specific heat capacity and conducts heat more efficiently than air.
As a result, water temperature strongly influences the physiological response to aquatic exercise.
Warm water may:
Increase comfort
Reduce perceived stiffness
Facilitate movement
Promote relaxation
Make exercise more tolerable for some people
However, excessively warm water can increase cardiovascular and thermal stress.
Therefore, pool temperature should be selected according to the patient's diagnosis, exercise intensity and medical status rather than assuming that "warmer is always better."
8. Respiratory Effects of Immersion
Chest-depth immersion increases hydrostatic pressure around the thorax.
This can increase the mechanical work required for breathing and alter lung volumes.
At the same time, immersion shifts blood toward the thoracic circulation.
These effects are important in patients with:
Significant pulmonary disease
Respiratory muscle weakness
Heart failure
Pulmonary hypertension
Other conditions in which increased central blood volume may be poorly tolerated
The physiological effects of immersion are therefore clinically important and not merely theoretical. (PubMed)
How Does Aquatic Therapy Work?
Aquatic therapy may produce therapeutic effects through several interacting mechanisms.
1. Reduced Weight-Bearing
Buoyancy decreases effective gravitational loading.
This can make movement possible when full land-based loading is painful or difficult.
Examples include:
Knee osteoarthritis
Hip osteoarthritis
Postoperative rehabilitation
Obesity
Lower-limb weakness
Some chronic pain conditions
2. Increased Resistance
Water resistance allows strengthening exercises without conventional weights.
Resistance can be increased by:
Increasing movement speed
Increasing limb surface area
Adding equipment
Increasing turbulence
3. Improved Mobility
Warm water and reduced loading may allow patients to perform larger movements with less discomfort.
This can be useful when pain or stiffness limits land-based exercise.
4. Balance Training
Water provides a unique combination of:
Reduced impact
Slower movement
Buoyant support
Multidirectional resistance
Adjustable instability
This can allow patients to practice balance strategies with a potentially lower consequence of losing balance.
5. Cardiovascular Conditioning
Water-based exercise can provide aerobic training while reducing some weight-bearing demands.
Walking, jogging, stepping and other movements can be progressed according to:
Speed
Duration
Water depth
Resistance equipment
Exercise complexity
6. Pain Modulation
Reduced mechanical loading, warmth, movement and exercise may all contribute to improved pain tolerance.
However, it is important not to attribute every pain improvement directly to a unique "healing" effect of water.
Much of the benefit may arise from enabling patients to exercise more comfortably and consistently.
What Does the Research Say?
The evidence for aquatic therapy is condition-specific.
It is not appropriate to say that hydrotherapy is equally effective for every musculoskeletal or neurological condition.
Aquatic Therapy for Osteoarthritis
Osteoarthritis is one of the better-studied applications.
A systematic review and meta-analysis of randomized controlled trials found that aquatic exercise improved pain, stiffness and physical function in people with knee osteoarthritis compared with no exercise immediately after treatment. (PubMed)
Another systematic review including people with osteoarthritis found reductions in pain and joint dysfunction and improvements in quality of life compared with control groups. (PubMed)
A Cochrane review of knee and hip osteoarthritis found small short-term improvements in pain, disability and quality of life compared with usual care or no exercise. (PubMed)
Importantly, aquatic exercise should not automatically be considered superior to land-based exercise.
For many patients, the major advantage is that water provides an environment in which exercise is more comfortable or feasible.
Clinical guidelines have included aquatic exercise as an exercise option for knee and hip osteoarthritis, without establishing it as universally superior to other forms of exercise. (PubMed)
Aquatic Therapy for Chronic Low Back Pain
Aquatic exercise is also used for chronic low back pain.
A 2024 systematic review and meta-analysis specifically examined water-based exercise in people with nonspecific chronic low back pain. The evidence supports water-based exercise as a potentially useful exercise approach, although outcomes vary according to the comparator, program and outcome measured. (PubMed)
The major practical advantage may be that water permits:
Walking
Trunk movement
Lower-limb strengthening
Aerobic exercise
Core exercises
while reducing the mechanical loading experienced on land.
Aquatic exercise should therefore generally be viewed as one exercise environment among several, rather than a replacement for appropriately prescribed land-based rehabilitation.
Aquatic Therapy for Fibromyalgia
Aquatic exercise has also been investigated extensively in fibromyalgia.
A 2024 systematic review found positive effects of aquatic exercise on pain and quality of life, while emphasizing that benefits may be similar to those achievable with other exercise approaches. (PubMed)
A systematic review with meta-analysis found short-term improvements in pain, fatigue, fibromyalgia impact, depression, physical function and mental health compared with no intervention. However, aquatic therapy was not demonstrated to be superior to land-based exercise, and certainty of evidence was low to very low for several outcomes. (PubMed)
This is clinically important.
For someone with fibromyalgia who finds land-based exercise uncomfortable, aquatic exercise may provide a more tolerable way to begin or maintain physical activity.
Aquatic Therapy in Neurological Rehabilitation
Aquatic therapy is increasingly used in neurological rehabilitation.
Potential applications include:
Stroke
Multiple sclerosis
Parkinson's disease
Neurological balance disorders
Gait dysfunction
The water environment can be useful because buoyancy decreases effective body weight while water resistance slows movement and provides sensory input.
Stroke
Systematic reviews have reported improvements in balance, gait speed and mobility following aquatic therapy, although the magnitude and clinical importance of these improvements vary.
A 2026 systematic review and meta-analysis including 27 studies and 1,134 participants reported improvements in balance, gait speed and fall-risk measures, but also emphasized substantial heterogeneity. (PubMed)
Another recent 2026 review found moderate evidence for improved balance but inconsistent evidence for some mobility outcomes and emphasized methodological limitations in the existing literature. (PubMed)
Therefore, aquatic therapy can be considered a potentially useful adjunct to neurological rehabilitation, rather than a replacement for task-specific land-based gait and balance training.
Multiple Sclerosis
Aquatic therapy has also been studied in multiple sclerosis.
Recent systematic-review evidence suggests potential improvements in fatigue, mobility, physical function and quality of life, but the number of randomized trials remains relatively small and interventions are heterogeneous. (PubMed)
Temperature management may be particularly important in people with multiple sclerosis because some individuals experience heat-related worsening of symptoms.
Indications for Aquatic Therapy
Aquatic therapy may be considered when the aquatic environment provides a meaningful rehabilitation advantage.
Common indications include:
Musculoskeletal conditions
Knee osteoarthritis
Hip osteoarthritis
Chronic low back pain
Chronic musculoskeletal pain
Joint stiffness
Reduced weight-bearing tolerance
Selected postoperative rehabilitation
Sports injury rehabilitation
Some chronic tendinopathies
General deconditioning
Neurological conditions
Stroke
Multiple sclerosis
Parkinson's disease
Neurological gait impairment
Balance dysfunction
General weakness associated with neurological disease
Functional rehabilitation
Difficulty walking on land
Reduced exercise tolerance
Obesity-associated movement limitations
Fear of falling
Balance retraining
Cardiovascular conditioning when medically appropriate
The indication should be based on the individual rehabilitation goal, not simply the diagnosis.
Contraindications to Aquatic Therapy
Aquatic therapy is not appropriate for every patient.
Contraindications and reasons to postpone or modify treatment can include:
1. Open or Unhealed Wounds
Immersion may be inappropriate when a surgical incision or wound has not adequately healed.
This is particularly important after surgery.
The timing of pool entry should follow surgical and wound-care guidance.
2. Active Infection
Patients with active contagious infections or conditions that could contaminate the pool should generally not participate until medically appropriate.
Therapeutic pools require appropriate hygiene and infection-control procedures. (PubMed)
3. Uncontrolled Incontinence
Urinary or fecal incontinence may require exclusion or specialized management depending on facility policy and the patient's ability to maintain hygiene.
Fecal incontinence is particularly important because of infection-control concerns.
4. Unstable Cardiovascular Disease
Patients with significant cardiovascular instability require medical assessment before immersion and aquatic exercise.
Immersion changes venous return, cardiac loading and central blood volume.
Neck-depth immersion can substantially alter cardiopulmonary physiology. (PubMed)
5. Significant Respiratory Instability
Patients with severe respiratory compromise may have difficulty tolerating chest-depth immersion because hydrostatic pressure increases the mechanical work of breathing.
6. Uncontrolled Seizures
A patient with poorly controlled seizures may face a serious drowning risk.
Aquatic therapy should only be considered with appropriate medical clearance, supervision and safety procedures.
7. Severe Cognitive or Behavioral Impairment
If a patient cannot follow safety instructions or maintain adequate behavior in the water, aquatic therapy may be unsafe unless sufficient trained assistance is available.
8. Fever or Significant Acute Illness
Acute systemic illness can make exercise and immersion inappropriate.
Treatment should generally be postponed until the patient is medically stable.
Precautions
Some conditions are not absolute contraindications but require careful assessment.
These include:
Controlled cardiovascular disease
Controlled hypertension
Diabetes
Peripheral vascular disease
Respiratory disease
Epilepsy with adequate control
Significant balance impairment
Osteoporosis
Pregnancy
Skin disorders
Reduced sensation
Fear of water
Recent surgery
Acute or chronic wounds
Heat sensitivity
Multiple sclerosis
Severe obesity
The physiotherapist should consider both the patient's medical status and the specific characteristics of the pool environment.
How Is an Aquatic Therapy Session Performed?
A typical session may follow several stages.
1. Pre-Session Assessment
The physiotherapist may assess:
Pain
Mobility
Strength
Balance
Gait
Cardiovascular status
Respiratory status
Surgical/wound status
Functional goals
Ability to enter and exit the pool
2. Pool Entry
Safe entry and exit are essential.
Depending on the patient's abilities, this may involve:
Steps
Handrails
Pool lifts
Therapist assistance
Appropriate flotation devices
Fall prevention begins before the patient enters the water.
3. Warm-Up
The patient may begin with:
Gentle walking
Marching
Active range of motion
Shoulder movements
Low-intensity functional movements
4. Therapeutic Exercise
Exercises are selected according to the patient's goals.
For example:
Strengthening
Hip abduction
Hip extension
Knee flexion/extension
Squats
Step-ups
Calf raises
Upper-limb resistance exercises
Mobility
Hip movements
Knee movements
Trunk rotation
Shoulder movements
Walking drills
Balance
Narrow-base standing
Weight shifting
Single-leg tasks when appropriate
Direction changes
Turbulence challenges
Gait
Forward walking
Backward walking
Sideways walking
Step training
Variable-speed walking
Cardiovascular conditioning
Water walking
Jogging
Step exercises
Interval-based aquatic exercise
How Is Exercise Progressed in Water?
One of the biggest advantages of aquatic therapy is the ability to manipulate several variables.
To Make Weight-Bearing Easier
Increase immersion depth.
For example:
Shallower water → greater weight-bearing
Deeper water → greater unloading
To Increase Resistance
The therapist can:
Increase movement speed
Increase limb surface area
Add aquatic equipment
Increase turbulence
Change direction of movement
To Increase Balance Demand
The therapist can:
Reduce hand support
Narrow the base of support
Change direction
Add turbulence
Introduce dual-task activities
Increase movement complexity
To Increase Cardiovascular Demand
The therapist can manipulate:
Movement speed
Duration
Exercise selection
Intervals
Resistance
while monitoring the patient's response.
Typical Duration and Dosage
There is no single universally correct aquatic therapy prescription.
Programs in clinical research commonly vary in:
Frequency
Session duration
Water temperature
Water depth
Exercise intensity
Program length
Many rehabilitation programs use approximately 2–3 sessions per week, with sessions commonly lasting around 30–60 minutes, but the appropriate dose should be individualized.
For a severely deconditioned patient, beginning with a shorter session may be more appropriate.
For a well-conditioned patient undergoing sports rehabilitation, longer or higher-intensity sessions may be appropriate.
The correct dose depends on:
Diagnosis
Irritability
Exercise tolerance
Cardiovascular status
Treatment goal
Stage of rehabilitation
What Does the Patient Usually Feel?
Patients commonly report:
Reduced feeling of body weight
Easier movement
Warmth
Reduced joint loading
Increased resistance during faster movements
A feeling of instability during balance exercises
Increased cardiovascular effort during more intense exercise
Aquatic exercise should not necessarily feel "easy."
A slow walking exercise may be relatively comfortable, while rapid movements against water resistance can produce substantial muscular and cardiovascular demand.
Benefits of Aquatic Therapy
Potential benefits include:
Mechanical benefits
Reduced effective body weight
Reduced joint loading
Multidirectional resistance
Adjustable exercise difficulty
Supported movement
Functional benefits
Gait training
Balance training
Mobility practice
Strengthening
Cardiovascular conditioning
Patient-related benefits
Exercise may be more comfortable
Reduced fear of movement for some patients
Greater ability to participate in exercise
Potential improvement in confidence
A different environment for progressing rehabilitation
The magnitude of these benefits depends heavily on the patient's condition and the quality of the exercise program.
Aquatic Therapy vs Land-Based Exercise
Aquatic and land-based exercise should not be viewed as competitors.
They offer different mechanical environments.
| Feature | Aquatic Therapy | Land-Based Exercise |
|---|---|---|
| Weight-bearing | Adjustable/reduced | Full gravity-dependent |
| Resistance | Water resistance | Gravity, weights, bands, machines |
| Impact | Generally lower | Can range from low to high |
| Balance | Supported but challenging | More directly reflects daily life |
| Gait practice | Possible | Essential for real-world walking |
| Strength progression | Speed/surface/equipment | Load can be quantified directly |
| Cardiovascular training | Possible | Possible |
| Fear of falling | Often reduced | May be greater initially |
| Functional specificity | Variable | Often higher for daily activities |
For many patients, the best approach is integration of aquatic and land-based rehabilitation.
Water can make early or painful movement more feasible, while land-based exercise can progressively restore the mechanical demands required for daily life.
Aquatic Therapy vs Swimming
These are not the same.
Swimming is primarily a locomotor and cardiovascular activity performed in a horizontal position.
Aquatic therapy is a structured rehabilitation intervention designed around specific impairments and functional goals.
Aquatic therapy may include:
Standing exercises
Walking
Balance training
Strengthening
Gait retraining
Functional movements
A patient can receive aquatic therapy without swimming.
Aquatic Therapy After Surgery
Aquatic rehabilitation can sometimes be useful after orthopedic procedures such as:
Knee surgery
Hip surgery
ACL reconstruction
Other lower-limb procedures
The major attraction is that buoyancy allows movement with reduced loading.
However, pool entry should not be based solely on time since surgery.
The wound must be appropriately healed, infection risk considered and the surgeon/clinical team’s restrictions followed.
Aquatic rehabilitation has also been proposed as a way to progressively restore gait, cardiovascular conditioning and movement after ACL reconstruction, although some of these recommendations are based on clinical commentary rather than high-level comparative evidence. (PubMed)
Safety Considerations
Safety should be treated as an essential component of aquatic therapy.
Important considerations include:
Pool temperature
Water depth
Patient supervision
Pool entry and exit
Floor slipperiness
Appropriate footwear
Flotation equipment
Emergency procedures
Infection control
Patient fatigue
Cardiovascular response
Respiratory response
Hydration
Patients should not assume that being in water eliminates fall risk.
Poolside falls can be particularly dangerous.
Limitations of Aquatic Therapy
Aquatic therapy has several limitations.
1. Access
Not every clinic has a therapeutic pool.
2. Cost
Aquatic facilities require significant infrastructure, maintenance and staffing.
3. Transfer to Land
Improvement in the water does not automatically mean equivalent improvement on land.
A patient must eventually practice the movements and loading requirements relevant to daily life.
4. Cardiopulmonary Demands
Immersion can produce substantial cardiovascular and respiratory changes.
Therefore, aquatic therapy is not automatically safer than land exercise for every patient.
5. Evidence Heterogeneity
Research protocols differ substantially in:
Temperature
Depth
Exercise type
Frequency
Duration
Intensity
Comparator treatment
This makes it difficult to identify one universal "optimal" aquatic therapy protocol.
Common Myths About Aquatic Therapy
Myth 1: "Aquatic therapy is only for elderly patients."
False.
Aquatic rehabilitation can be used across age groups, including athletes, postoperative patients and people with neurological or chronic musculoskeletal conditions.
Myth 2: "Water automatically makes exercise easy."
False.
Buoyancy can reduce weight-bearing, but water resistance increases with movement speed and can create significant muscular demand.
Myth 3: "Aquatic therapy is better than land exercise."
Not necessarily.
Evidence supports aquatic exercise for several conditions, but superiority over land-based exercise is not consistently demonstrated.
For fibromyalgia, for example, systematic-review evidence found benefits compared with no intervention but did not establish superiority over land-based exercise. (PubMed)
Myth 4: "Aquatic therapy replaces normal walking practice."
False.
For a patient whose goal is independent community walking, land-based gait training remains important.
Aquatic gait training can be an adjunct.
Myth 5: "The warmer the pool, the better."
False.
Temperature should be selected according to the patient, exercise intensity and medical condition.
Excessive heat can create unwanted cardiovascular or thermal stress.
Frequently Asked Questions
Is hydrotherapy the same as aquatic therapy?
The terms are often used interchangeably, but aquatic therapy usually refers more specifically to therapeutic exercise and rehabilitation performed in water.
Hydrotherapy is a broader term that can encompass several therapeutic uses of water.
Does aquatic therapy reduce pain?
It can.
Evidence supports improvements in pain for conditions such as osteoarthritis and fibromyalgia, although the magnitude of benefit varies and aquatic therapy is not necessarily superior to other exercise approaches. (PubMed)
Can aquatic therapy build muscle?
Yes.
Water provides resistance, and exercise can be progressed by increasing movement speed, surface area, turbulence or equipment.
However, conventional progressive resistance training on land may provide more precise and measurable loading when substantial strength gains are the primary goal.
Is aquatic therapy good for knee osteoarthritis?
Yes, it can be a useful exercise option.
Systematic reviews report improvements in pain, stiffness and physical function, particularly compared with non-exercise controls. (PubMed)
Can aquatic therapy help chronic low back pain?
Yes.
Water-based exercise has evidence supporting its use in chronic nonspecific low back pain, although the exact magnitude of benefit depends on the exercise program and comparison group. (PubMed)
Can stroke patients do aquatic therapy?
Many can, provided they are medically stable and can participate safely.
Evidence suggests potential improvements in balance and some gait-related outcomes, but aquatic therapy should generally complement rather than replace land-based neurological rehabilitation. (PubMed)
Can patients exercise in water after surgery?
Sometimes.
The incision must be appropriately healed, infection risk must be considered, and surgical restrictions must be followed.
The exact timing depends on the procedure and individual healing.
Is aquatic therapy safe for heart patients?
It depends on the individual's cardiovascular condition.
Immersion substantially changes cardiovascular physiology, particularly at greater depths. Patients with significant or unstable cardiac disease require appropriate medical assessment before aquatic therapy. (PubMed)
Does aquatic therapy help balance?
It can.
Water can provide a controlled environment for balance practice, and systematic reviews in conditions such as stroke have reported improvements in balance. However, evidence quality and clinical significance vary. (PubMed)
Evidence-Based Takeaway
Hydrotherapy / aquatic therapy is a physiotherapy environment rather than a single exercise.
Its therapeutic effects arise from the interaction of:
Buoyancy
Hydrostatic pressure
Water resistance
Viscosity
Turbulence
Temperature
Reduced gravitational loading
Altered cardiovascular and respiratory physiology
The strongest clinical rationale is often not that water has a universal healing effect, but that the aquatic environment allows a therapist to modify mechanical loading and exercise demands in ways that may be difficult to achieve on land.
Evidence supports aquatic exercise for conditions such as osteoarthritis, chronic low back pain and fibromyalgia, while neurological applications such as stroke and multiple sclerosis show promising but heterogeneous evidence. (PubMed)
The most clinically useful approach is usually to treat aquatic therapy as one component of a broader rehabilitation program, progressing the patient toward the strength, balance, mobility and functional demands required on land.
Final Thoughts
Aquatic therapy demonstrates how the physical environment can be used as a therapeutic tool.
Water can simultaneously unload joints, resist movement, challenge balance, influence circulation and provide thermal effects.
That combination makes it particularly valuable when a patient cannot yet tolerate the mechanical demands of conventional exercise.
But effective aquatic therapy requires more than putting a patient in a warm pool.
The physiotherapist must understand the physics of immersion, select an appropriate water depth and temperature, control resistance and turbulence, monitor physiological responses and progressively transition patients toward functional land-based activity.
Used appropriately, aquatic therapy can provide a highly adaptable bridge between limited movement and progressive functional rehabilitation.
Selected References
Becker BE. Aquatic therapy: scientific foundations and clinical rehabilitation applications. PM&R. 2009. PMID: 19769921. (PubMed)
Pendergast DR, Moon RE, Krasney JJ, et al. Human Physiology in an Aquatic Environment. Comprehensive Physiology. 2015. PMID: 26426465. (PubMed)
Weenink RP, Wingelaar TT. The Circulatory Effects of Increased Hydrostatic Pressure Due to Immersion and Submersion. Frontiers in Physiology. 2021. PMID: 34349668. (PubMed)
Lu M, et al. Effects of Aquatic Exercises for Patients with Osteoarthritis: Systematic Review with Meta-Analysis. PMID: 35327038. (PubMed)
Lim JY, et al. Efficacy and safety of aquatic exercise in knee osteoarthritis: A systematic review and meta-analysis of randomized controlled trials. PMID: 36320162. (PubMed)
Bartels EM, et al. Aquatic exercise for the treatment of knee and hip osteoarthritis. Cochrane Review. PMID: 27007113. (PubMed)
Babiloni-Lopez C, et al. Water-Based Exercise in Patients With Nonspecific Chronic Low-Back Pain: A Systematic Review With Meta-Analysis. 2024. PMID: 38085630. (PubMed)
Rodríguez-Huguet M, et al. Aquatic Exercise in Physical Therapy Treatment for Fibromyalgia: Systematic Review. 2024. PMID: 38540665. (PubMed)
Correyero-León M, et al. Effectiveness of aquatic training based on aerobic and strengthening exercises in patients with fibromyalgia: systematic review with meta-analysis. PMID: 37460329. (PubMed)
Gento-Andrés L, et al. Efficacy of Aquatic Therapy in Improving Balance in Patients With Stroke: A Systematic Review and Meta-Analysis. 2026. PMID: 41834815. (PubMed)
Effects of Aquatic Therapy on Balance and Gait in Chronic Stroke: A Systematic Review with Exploratory Meta-Analysis. 2026. PMID: 42042758. (PubMed)
Effects of Aquatic Therapy on Fatigue, Mobility, Physical Function, and Quality of Life in People with Multiple Sclerosis: A Systematic Review and Meta-Analysis. 2026. PMID: 42346748. (PubMed)
