Abstract

Objectives The aim was to evaluate an Acceptance commitment therapy (ACT) intervention for people
with knee or hip osteoarthritis; a related aim was to compare treatment effects from Rasch-transformed
and standard scales. Methods Participants were recruited from a research database and outpatient
rheumatology and orthopaedic clinics at two hospitals. Eligible participants were randomly allocated to
either intervention or usual care. Intervention comprised six-sessions of group ACT. Outcomes were
assessed two and four months after randomization. Rasch-transformed and standard self-report measures
were compared. Qualitative interviews also explored the acceptability of the intervention. Results Of 87
people assessed for eligibility, 31 (36%) were randomized. The main reason for non-randomization was
that participants received surgery. Of the 16 participants randomized to intervention, 64% completed
�50% of the scheduled group sessions. Follow-up data was complete for 84% participants at two months
and 68% at four months. Outcome analysis demonstrated important differences between the Rasch-transformed
and standard scales. There were significant differences between the groups in pain. Qualitative
interviews with seven participants suggested the intervention was acceptable. Conclusions ACT for osteoarthritis
is likely to be an acceptable treatment option for people with osteoarthritis. Progress to a definitive
trial is warranted. Rasch-transformed outcome scales are preferable in clinical trials where possible.