ISSN 2398-2977      



Graham Munroe

Kate Hesse


  • Hydrotherapy is commonly used in people for managing musculoskeletal injuries and reducing compensatory gait abnormalities.
  • Hydrotherapy is an effective technique for increasing joint mobility, enhancing muscle activation, improving postural control, reducing the incidence of secondary musculoskeletal injuries, and reducing inflammation. In humans with lower limb osteoarthritis treated by hydrotherapy, an increase in limb-loading, improved joint motion, and significant reductions in balance deficits have been seen. In addition, the improvement in muscle strength and function is important in these cases.
  • It is widely used in equine patients but scientific evidence for its efficacy is limited. Most of the equine literature focuses on the physiological benefits of exercising in water rather than on the effect on pathological mechanisms.
  • In the equine patient, the modalities of hydrotherapy most often used are underwater treadmill exercise (overground or in-ground units), and swimming (circular or straight pools). In addition, cold water therapy Cold therapy (cold water application or immersion such as standing salt water spas or whirlpools) has been extensively used in treating acute soft tissue inflammation, pain, and swelling.
  • Treadmill and swimming exercise are reported to reduce stresses placed on limbs, improve the range of motion of joints, improve muscle aerobic capacity and strength, increase cardiovascular endurance, and decrease pain and inflammation.
  • The physical properties of the water may be varied to individualise the therapeutic effects. These include increased buoyancy, hydrostatic pressure, and viscosity, and variations in temperature and osmolality:
    • The increased buoyancy and resistance in hydrotherapy improves joint stability and reduces weight-bearing on muscles and joints.
    • Immersion in water leads to circumferential compression, in proportion to the depth of water, which increases extra-vascular pressure promoting circulation and reducing oedema.
    • Varying the temperature of the water may lead to different effects. Warm water causes vasodilation, increased circulation, and decreased muscle spasm. Cold water reduces inflammation by decreasing blood flow and inflammatory mediators.
    • Increasing the osmolarity of the water will help reduce oedema and therefore pain.
  • In-ground underwater treadmills are capable of holding a greater amount of water and provide more buoyancy when compared to above-ground versions, whilst the latter allows the depth of water to be changed between each patient thereby targeting the rehabilitation protocols. Both versions come with hydrojets which create additional turbulence, increasing limb resistance, whilst the speed, water temperature, and solute concentration can also be varied.
  • Swimming pools for horses are either linear or circular shaped with ramps for entry/exit . The handlers usually walk along each side of the horse’s head with long reins connected to the head collar. Depths greater than 12 feet ensure complete buoyancy. Linear pools allow the horse to recover at the end of each length, whilst circular pools lead to continuous laps until the session is finished. As such the latter increases cardiovascular stress.
  • Aquawalkers are mechanical walkers set within a circular pool, which has a consistent depth of water but which is not variable . Most systems can accommodate 6-8 horses at a time. They are more designed as a way of exercising horses generally rather than as part of a physiotherapy treatment Musculoskeletal: physiotherapy.


  • Swim training helps improve cardiovascular function, reduces musculoskeletal injury such as tendinitis DDFT: tendinitis, and increases fast-twitch muscle fibers which leads to improved aerobic function. It is particularly useful in providing a medium to high-intensity workout without subjecting the musculoskeletal system to high levels of concussive force. This enables the horse to maintain some of its cardiovascular fitness whilst allowing its injury to heal, or cab be used to help train horses that have ongoing orthopedic problems.
  • Underwater treadmill walking affects the stride parameters depending on the depth of water. By varying the depth of water, joint-specific increases in ranges of motion can be achieved leading to specific protocols to target individual joints. Thoracolumbar lateral bending, pelvic flexion, and axial rotation are also influenced by the depth of water in the treadmill.
  • A specific study of underwater treadmill exercise in an experimentally induced carpal OA model was carried out and revealed improvements in passive carpal flexion, return to full range of motion, and improvements in limb loading and static balance. At a tissue level there was reduced capsular fibrosis and a decreased inflammatory infiltrate in the synovial membrane.


  • Reduce stresses placed on limbs.
  • Improved range of motion of joints.
  • Improved muscle aerobic capacity and strength.
  • Increased cardiovascular and respiratory endurance.
  • Reduce distal limb swelling and edema.


  • Horses are not particularly good swimmers and normally swim in a trotting gait. The back of the horse is held just underneath the surface of the water, with the head raised and the nostrils shut except during inhalation. They tend to use their hind limbs for propulsion in extreme ranges of motion, especially in the lumbosacral, hip, stifle and hock joints. On entry into the water they may adopt postures that extend the cervical, thoracolumbar and pelvic regions. Swimming should therefore be used with caution in horses with back, pelvic, hip, stifle and hock problems.
  • Swimming is a vastly different biomechanical activity to overground locomotion and cannot be used as the sole means of athletic preparation for racing and other sporting endeavours. Even the respiratory pattern is entirely different to gallop. Swimming does not mimic the horse’s anatomical position on land, nor does it promote an increase in bone density, or tendon and ligament strength, and therefore it can only be part of a varied training programme.
  • Swimming should not be used in horses with respiratory disease because increased hydrostatic pressure decreases lung volume and affects ventilation.
  • Aquatic therapy in general should not be used in the following situations:
    • unhealed surgical incisions
    • open infected and draining wounds
    • proximal pelvic limb lameness
    • thoracolumbar pain or injury
    • acute joint inflammation
    • acute myositis
    • elevated temperature
    • fearful or nervous horses
    • cardiovascular compromise.
  • Horses should not be swum in water that is near or above their body temperature as they will not be able to dissipate heat from their body which is generated by exercise. As such the water is usually heated to between 12°C/53.6°F and 19°C/66.2°F.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • King M R (2016) Principles and application of hydrotherapy for equine athletes. Vet Clin Equine 32 (1), 115–126 PubMed.
  • King M R et al (2013) Mechanisms of aquatic therapy and its potential use in managing equine osteoarthritis. Equine Vet Educ 25 (4), 204-209 VetMedResource.
  • Buchner H & Schildboeck U (2006) Physiotherapy applied to the horse: a review. Equine Vet J 38 (6), 574-580 PubMed.

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