Physiotherapists have an important role to play in the clinical management of osteoarthritis (Green et al, 1993) however, the effect of their involvement has rarely been assessed in terms of randomised controlled trials. Chard et al (2000) examined the research output in relation to a number of physiotherapy interventions available to patients with osteoarthritis of their knees and established that between 1950 to 1998 only 60 research articles were published, the majority of which occurred between 1985 and 1998. Advice (Maurer et al, 1999; Manek and Lane, 2000) and exercise (Puett and Griffin, 1994; Clarke, 1999; O'Reilly et al, 1999) have been clearly identified as beneficial in terms of relieving the impairments experienced by individuals with knee osteoarthritis. Indeed there is a some evidence supporting the use of a number of physiotherapy interventions including hydrotherapy (Ahern et al, 1995; Norton et al 1997; Alexander et al, 2001) and continuous short-wave diathermy (CSWD) (Wright, 1964; Lankhorst et al, 1982) for the treatment of knee osteoarthritis but there are difficulties regarding the design of many of these studies thus undermining the conclusions that have been drawn. This study presents the results of a randomised controlled factorial trial (Polger and Thomas, 2000) designed to examine hydrotherapy and/or continuous short wave diathermy (CSWD) for patients with knee osteoarthritis while also examining the perceptions of patients participating in a physiotherapy programme.