Aquatic Physical Therapy for Hip & Knee Osteoarthritis

osteoarthritis ward kneesWhat is Osteoarthritis?

Osteoarthritis (OA) is a progressive disease in the joints affecting nearly one third of the elderly population, with future estimates indicating a significant rise in occurrences for the ageing population. Frequently reported with Osteoarthritis , patients experience joint pain, stiffness, loss of physical function, and muscle weakness, among other symptoms. Typical management for OA includes physical therapy (Day, Heywood, & Hinman,2007).

Practical use of Hydrotherapy has been prevalent for approximately 16 centuries. Within the last hundred years, significant advances have been made in the line of treatments using hydrotherapy. Musculoskeletal therapy applications of hydrotherapy include therapeutic and exercise activities in a heated pool. The buoyancy in water reduces weight loaded on pain-affected joints, and water turbulence can be used as resistance as a supplement for weights. Further assisting with the pain and swelling, the hydro-therapist can adjust the pressure and temperature of the water (Day et al., 2007).


This study was designed to address the limitations of previous studies, where little consideration was given to hydrostatic or hydrodynamic principles, which reduced the potential for benefit for the participant. Additionally, previous studies have typically didn’t evaluate a sample based specifically on knee or hip osteoarthritis alone. The study hoped to use a functional progressive intervention on their groups in a controlled trial with intention-to-treat analysis, using the properties of water to optimize outcomes. Through this 6 week program, the aim was to measure improvements in pain and physical function of participants with OA in their hip, knee, or both. The study would put these results against a control group with no aquatic physical therapy. Additionally, the study would determine if participants continued a therapy regiment independently after the initial 6 week program, and a follow up to see which benefits were maintained during a follow-up another 6 weeks later (Day et al., 2007).

Osteoarthritis hip diagramThe study searched for participants that were over 50 years old, with hip or knee osteoarthritis. Advertisements were placed in several venues to recruit participants, including libraries, doctors’ offices, orthopaedic clinics, and within both print and radio media. The study excluded potential participants that showed specific contraindications, such as significant back pain, recent joint injections, recent surgery, lower-limb joint replacement, and those that were unable to safely enter and exit a pool. 312 volunteers signed up and were screened, of which 71 were selected by fitting the criteria and were subsequently enrolled in the study. An intervention group of 36 was established, with a control group of 35 also created with a plan that they would receive the aquatic treatment after the study in exchange for simply continuing their normal routine for the 6 week process. As a sample size, 71 participants were selected in order to achieve a statistical significance level of 5% to detect difference of pain of 2 cm (discussed later in the outcomes), allowing for participants that may drop from the program (Day et al., 2007).

Immediately before the treatment, participants were assessed for the standards of the study. They were again assessed immediately after the 6 weeks, and again at 12 weeks. This protocol would allow assessment of which benefits were maintained in the long term, as well as the likelihood of continued independent aquatic therapy by the participants (Day et al., 2007).

The intervention group went through 6 weeks of exercises in a hydrotherapy setting, provided twice weekly in sessions that were approximately one hour each. With a maximum of six participants per session, the therapist emphasized quality of movement while working on balance and strength. The participants were tracked and individual progression was determined by the therapist. During this six-week program, the participants were asked to keep a log of their sessions. Following the study, they were encouraged to continue independent aquatic therapy twice weekly. In addition, the participants were instructed to continue their usual medication for the entirety of the 12-week period (Day et al., 2007).


The outcomes that were measured from this study include subject-perceived changes in pain and physical function, muscle strength, balance, and gait. Using a visual analogue scale measured in 1 cm increments, these metrics were rated by the participants and interpreted by the team giving the study. While rating pain, a scale of 1-5 was used to show improvement, 5 indicating the greatest improvement. To test for physical function, the participants were asked to stand up from a sitting position, walk 3 metres, and return to the chair while walking at their own pace (Day et al., 2007).

OA progression

Muscle strength was measured as peak strength, assessed three times and recorded the highest score. Balance was tested by having the participant stand barefoot on the affected limb, and move their other foot up to a 7.5 cm step and back as many times as possible for 15 seconds. For the balance test, the individuals were not required to move body weight, and those receiving higher number of steps were scored as better balance. To test gait, participants were evaluated on how far they could walk within a 6 minute time-frame. They walked back and forth over a 50 metre stretch, and their total distance was measured and recorded (Day et al., 2007).


The primary results of this study indicated that pain from movement was reduced by 33% from baseline assessment, which demonstrates significantly less pain at 6 weeks for the intervention group than the control group. Seventy-two percent of the intervention participants reported a global improvement in pain, compared to only seventeen percent in the control group. For global improvements in physical function, seventy-five percent of the intervention group responded positively, while seventeen percent of the control group participants responded the same (Day et al., 2007).

At the 6-week mark, intervention participants reported significantly less pain. Hip muscle strength and quality of life were rated as significantly greater as well. During the follow up six weeks later, 84% of participants reported that they had continued to seek independent aquatic physical therapy. 45% of the group attended one or two times per week, and another 15% attended 2 or 3 times per week. The rated scores at the 12 week mark showed that the overall ratings were generally unchanged from scores obtained at 6 weeks, indicating that benefits of the program were maintained in the short term, but with continued therapy, would remain with decreased pain and better physical function (Day et al., 2007).


With a relatively small sample size, it’s difficult to specifically say that aquatic therapy is superior to similar therapy based on land. The study identified limitations, including the lack of placebo, which yielded a single-blind design and therefore may have skewed the results. The chronic nature of osteoarthritis also warrants longer evaluation periods for further examination and statistical testing. In this study, participants were only using their own body weight and the resistance of the water. It was noted that additional items such as swim fins and floatation devices may have been used to increase resistance and improve strength and muscle functions (Day et al., 2007)

In a clinical setting, the results from this study can be applied by making reference to the time-line for decrease of pain in a patient. In practice, standard physical therapy may prove to be too physically straining, in which case, a physical therapist assistant could discuss the option of aquatic therapy to the physical therapist, specifically noting the decreased stress on osteoarthritic joints, and the combination of turbulence and water temperature in their beneficial manner in regards to weight bearing. Once on a plan for aquatic therapy, the physical therapist assistant could have a better understanding of expectations for results in the pain management sector of the treatment plan as designed by the physical therapist.


Day, A. R., Heywood, S. F., & Hinman, R. S. (2007). Aquatic physical therapy for hip and knee osteoarthritis: Results of a single-blind randomized controlled trial. Physical Therapy, 87(1), 32+. Retrieved from|A157267508&v=2.1&u=lirn09099&it=r&p=PPNU&sw=w&asid=47d97cd364b4dbe1fe318cd8dee9b374


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