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Influence of various recruitment strategies on the study population and outcome of a randomized controlled trial involving patients with osteoarthritis of the hip or knee.

OBJECTIVE
To examine the effect of 2 different recruitment methods on the characteristics of participants with osteoarthritis (OA) of the hip or knee and on the efficacy of an exercise program.


METHODS
In a clinical trial on the effectiveness of exercise therapy in OA of the hip or knee, 2 groups of patients were recruited: one group through referrals by physiotherapists (PT group, n = 110) and one group invited by newspaper articles (NP group, n = 90). At baseline, demographic, clinical, and psychosocial data were collected and compared between the 2 groups using chi-square and Student's t-tests. After 13 weeks of exercise therapy and followup assessments at weeks 39 and 65, the main outcome measures (pain, physical function, and global perceived effect) were assessed and compared by multiple regression analysis.


RESULTS
The NP group reported less pain and tiredness at baseline, although more joints were affected with osteoarthritis. The PT group scored higher on the scale 'powerful-others' of locus of control. After adjusting for baseline differences, the effect of treatment after 13, 39, and 65 weeks was comparable for both groups for all outcome measures.


CONCLUSION
Recruitment method affects clinical characteristics and physical functioning of patients recruited for the study. A mix of recruitment strategies does not seem to affect treatment outcome, on the condition that adjustments are made for baseline differences.