Hydrotherapy & Aquatic Equipment for a Knee Replacement


The must have information about water therapy prior to a Knee Replacement (prehab) and post (recovery).

Overview of Knee replacement

A knee replacement, also referred to as a knee arthroplasty or total knee replacement, is a surgical procedure to resurface a knee. Having knee replacement surgery is incredibly common all over the world. The most common joint replaced is the knees. The Australian Orthopaedic Association National knee Replacement Registry reports 62,624 knee replacement surgeries in 2020.

A knee replacement is an orthopaedic surgical procedure that helps people with severe arthritis or knee dysfunction and is often the last resort for those who have damage to a knee or a reduction in mobility. Knee replacement surgery is deemed necessary when the knee is worn or damaged. Your mobility will be reduced, and you will experience pain while resting.

There are so many reasons that a person could require knee replacement surgery, including:

• Osteoarthritis

• Injury

• Rheumatoid arthritis

• Hemophilia

• Death of a bone in the knee following blood supply complications

• Gout

• An abnormal bone growth as a result of another medical condition

• Deformity with pain and loss of cartilage

Once a Orthopaedic specialist has diagnosed that the knee is beyond any other realm of treatment the surgical option will most likely be recommended for either a full or partial replacement. This is to assist the patient in future ease of movement and pain-free mobility. More than 90 percent of those people who have had a knee replacement proceedure say it significantly reduced their knee pain and improved their quality of life.

When having knee replacement surgery, prehab and recovery/rehabilitation are essential. They help to get back on to your feet and able to do all the things you want to do to live an dactive and fullfilled life as quickly as possible.

What is a Knee Replacement?

A knee athroplasty, or replacement, is a surgical procedure that aims to replace the knee or knees in your body with an artificial prosthetic knee. 

There are three types of knee replacement proceedures. These include:

• a total knee replacement (TKR): where the whole knee is replaced

• a partial knee replacement (PKR): only a affected portion of the knee is replaced

• bilateral knee replacement (BKR): both knees are replaced together at the same time

A knee replacement is given to patients with compromised knee mobility and functionality. 

Prehabilitation prior to knee surgery aims to improve the patient's strength and mobility of support structures before they undergo surgery. Recovery and rehabilitation is what they experience post-surgery to get the knee joint engaged and returning to a better function. Together, both these processes can help people to return to an improved knee function and quality of life as quickly as possible.

When to consider a Knee Replacement

There are many reasons behind knee replacement surgery, the largest being Osteoarthritis. Osteoarthritis is characterised by the deterioration of the joint cartilage. Damage to this cartilage and the bones limits movement and causes pain in the knee. Those with severe degenerative joint disease may be unable to perform normal activities on land that require bending at the knee, kneeling, walking or climbing stairs, because they are too painful. The knee may give-way or swell because the joint is not stable. Between 2005/6 and 2017/18 there has been a 38% increase in the instances requiring a knee replacement as a result of osteoarthritis. In just over a decade, the number of people requiring a total knee replacement has increased by over a third.

Damage to your knees can cause chronic and significant pain, not just in the affected knee but also often in the surrounding knees, muscles, and tendons. Its not uncommon for other parts of the body, particularly the other knee to compensate as it takes more of the load.  

Severe pain and its side affects is one of the main reasons many seek or are recommended a knee replacement. Still, it isn't the only symptom that could indicate your need for knee replacement surgery.

Any of the following may apply:

• You regularly take painkillers to alleviate the pain

• Your pain levels keep you awake at night despite the use of analgesics

• Your pain makes it difficult to walk correctly or perform more complex movements, such as bending down or kneeling

• Your pain isn't relieved by taking rest, either during the day or night

• Conservative prescribed treatments have not alleviated your pain levels

• You make compensatory movements to reduce the pain, such as walking with a limp

• You may rely on a walking aid to relieve your knee pain

Water Therapy & a Knee Replacement


Movement and exercise can play a vital role in preventing knee damage, supporting the knee during treatment, and recovery.

Exercise can help to prevent further knee joint damage by:
• strengthening the muscles around the knee.
• strengthening the knees support structures ie quads, glutes, other knee, ankles & hips.
• helping to maintain a healthy weight

This is true both before and after knee surgery, whether for the natural or the new artificial knee.

Chronic pain and mobility issues can also increase the risk of social isolation. Joining an group fitness class is a good way to connect with other people, some of whom may have similar health issues.

Water Therapy

Water therapy aids in knee replacement rehabilitation by alleviating pain, reducing swelling, and speeding up rehabilitation time. It also significantly improves the range of motion and helps with inflammation.

Water provides a safe environment and is perfect for knee prehab and rehabilitation due to its consistent temperature, buoyancy, density, pressure, and resistance. It also helps to reduce body weight (and thus pain) and relax the muscles.

The water is an excellent environment for larger people as less weight baring than any form of land exercise.

The buoyant nature of water reduces bodyweight, making walking and functional movements easier after a surgical proceedure.

The hydrostatic pressure generated by the water has positive effects on reducing swelling and inflammation in the knee . This helps to regain more range of motion and reduces the persons pain.

Heated water significantly enhances and speeds up the recovery process post surgery. The heat relaxes the muscles and tendons surrounding the knee, enabling a natural healing and a smooth movement. There are further positive influences on pain regulation due to the relaxation effect of heated water and suppression of the sympathetic nervous system that occurs with water submersion.

The sensory nature of the water can also improve body position enabling improved feelings of balance and confidence to move.

These properties of water have been proven to help with pain levels in the prehabilitation of those who need knee replacements - as well as improve overall health before or after surgery.

Water Therapy for a Knee Replacement

With the routine consistency of specialised knee replacement water therapy programs, improvements can be gained in these areas:

Knee Prehab
• Slow the deterioration of the knee joint.
• Build support structures for the knee, glutes, quads, ankles, and hips.
• Minimise pain and discomfort.
• Keep the person's weight down. Every 1 kg is 3kgs on the knee.
• Reduce swelling, stiffness, and knee stress.
• Reduce impact on compensating muscles.
• Reduce the risk of injuries due to unstable joints that are common on land.

Knee Recovery/Rehabilitation
• Reduce the risk of injuries or falls.
• Minimise pain and discomfort.
• Reduce swelling, stiffness, and knee stress.
• Speed up recovery time.
• Get an exclusive natural range of motion.

Water Therapy Equipment & a Knee Replacement

Underwater Bike

Hydrorider Aqua Bike is an incredible aquatic invention that alleviates painful exercise before and after a knee replacement and improves the speed and quality of knee surgery outcomes.

How can an Underwater Bike assist Knee Surgery Prehab?

Slow the knee joint deterioration: When cycling in water, you are buoyant, have no gravity, and put less impact on the knee joint. The less pressure on the joint, the slower the deterioration.

Build support structures for the knee joint: The resistance of the water combined with movement allows you to build strength. You can safely work out at a high intensity and challenge yourself. Aqua Cycling builds even strength in the lower limbs (both legs). An AquaBike builds lean muscle strength in the glutes, quads, ankles, and hips, which support the knee joint before surgery.

Keep the person's body weight down: Every 1 kg is 3kgs of force on the knee. Extra weight and impact on the body puts the knee joint under stress and will increase the speed of deterioration. Water Cycling allows you shed a few kgs (up to 800 per hour) without putting pressure on the knee joint. If you can reduce your weight, you are reducing the impact on the knee when on land and moving in daily life.

Reduce swelling, stiffness, and knee stress: The hydrostatic pressure and gentle massage from the water help to reduce the inflammation that makes the knee joint painful and hard to move. The water movement and warmth enhance the blood flow, and rotation improves circulation to the legs, reducing stiffness and increasing mobility. The water's buoyancy and the support provided by the AquaBike structure remove impact from the knee, and the warm water relaxes the muscles removing any knee stress.

Reduce impact on compensating muscles: When cycling in water, there is no impact on the joints or pain, enabling a correct exercise movement and use of the joint. This means no compensation is required, and exercise doesn't add additional load to compensating muscles, causing pain and injury elsewhere.

Minimise pain and discomfort: Immersion on the knee on an Aquabike in water decreases the impact on your knees during exercise, which means you will be able to do lots more strength building with less pain. The sympathetic nervous system is suppressed in water submersion, resulting in a reduction in pain. If the water is heated, the muscles and mind also relax, helping to reduce pain or discomfort.

Reduce the risk of injuries: Cycling in water reduces the instances of potential falls from failing knees and tired muscles from land-based impact cycling or weight-bearing exercises. When exercising on land with bad knees, other muscles and joints often compensate and alter the proper movement resulting in additional injuries.

Relax the whole body and mind: Anxiety about upcoming surgery is expected, and the calming, soothing properties of water can reduce the level of anxiety. Specialised water cycling prehab sessions can also put the person at ease, knowing they have done what they can in preparation for the best possible outcome.

How can an Underwater Bike assist Knee Surgery Recovery/Rehabilitation?

Reduce the risk of injuries or falls: There are fewer impacts on your body when cycling in water. You're submerged in water, so you can move without worrying about damaging your new knee or falling. There is no touching of the person or manipulation of the knee joint. The movement is natural and assisted by water. There are very few post-surgical joint dislodgements or complications with water-cycling-based recovery than other forms of knee rehabilitation.

Minimise pain and discomfort: The buoyancy of the water helps to lessen the impact that exercises have on your knee while still giving a full range of motion, so you aren't introducing too much too soon, which is one of the leading causes of pain postoperatively. Immersion in water decreases the impact on your knees during exercise, which means you will be able to do lots more strength building with less pain. There are other positive influences on pain regulation due to the relaxation effect of heated water and suppression of the sympathetic nervous system that occurs with water submersion. 

Reduce swelling, inflammation, stiffness, and knee stress: The hydrostatic pressure and gentle massage from the water help reduce the post-surgical swelling and inflammation that makes the knee joint painful and hard to move. The water movement and warmth enhance the blood flow, and rotation improves circulation to the new joint and reduces stiffness. The water's buoyancy combined with the AquaBike support structure removes impact from the knee, and the warm water relaxes the muscles removing any stress from the knee. It allows the knee to recover from the trauma of surgery while gently guiding it and building strength to return to a better function. 

Get a natural/gentle range of motion: The heat relaxes the muscles and tendons surrounding the knee and enables natural healing and fusing with the joint and a smooth noninvasive rotation. With the Hydrorider Aquabike Flywheel, a rotation with the new knee is not forced or manipulated; it gently eases when ready, typically after 15mins in 1 or 2 water cycling sessions. The structure of an AquaBike provides alignment and rotation momentum, ensuring a maximum range of motion. This Hydrorider flywheel is what guides the triumphant return to movement post-surgery. There is no mechanical (knob resistance) on the Hydrorider resistance is self-driven and increases with speed. This ensures too much resistance/weight load isn't added too soon for the individual. As the new knee gets more robust and the person naturally increases speed resistance increases. This ensures the person can only do what the joint is ready for, and no excessive force or resistance is added that would create too much stress too soon.

Relax and enjoy the journey: Anxiety and impatience about returning to work and everyday activity as quickly as possible are common. The calming, soothing properties of water can reduce anxiety and relax the mind. The visually apparent rotation and mobility improvements help motivation, reduce impatience, and many often say they have enjoyed the recovery process.

Speed up recovery time:

One of the best benefits of water cycling for knee replacements is speeding up recovery time. When you go through knee replacement surgery, your body goes through many different changes. Your knees are no longer working correctly, and you need to learn how to use them again. Immersing the knee in water helps alleviate some of the pain and pressure on your muscles, giving you more range of motion without undue stress on your new knee. Because of this, you can do more sooner, but resistance is guided by your knee activation, so there are fewer setbacks from doing too much too soon. Rotation and strength gains are faster on an Hydrorider than on a land bike or with specialised weighted exercises. This speeds up the recovery process to return to your feet sooner rather than later. Heated water significantly enhances and speeds up the recovery process post-surgery.  

Underwater Treadmill

Hydrorider Aqua Treadmill is also a superb piece of equipment that can help pre and manageability of a post-operative knee replacement. It is a great tool to enable larger body frames or overweight people to get a natural walking movement without being fully weight-bearing. An underwater treadmill is helpful in the early days post-surgery for larger body frames or unconfident people.

It is also an excellent tool for runners who want to continue running prior and slow the deterioration without impacting the knee joint or risking an injury. It is also a great way to ease back into running after a replacement and before pounding the pavement.

Note: Please seek medical advice before exercising & always train under the advice your medical specialist.


Woman water cycling post a knee replacement
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