The participants were recruited in the outpatient clinic of the Department of Orthopaedics and Trauma Surgery, Musculoskeletal University Center Munich (MUM), LMU Munich. Written informed consent was obtained from each participant. The study was approved by the local ethics committee and registered with the German Clinical Trials Register (DRKS00021827).
Inclusion criteria were a clinical diagnosis of osteoarthritis of the hip and/or knee joint confirmed by x-ray and age ≥ 18 years. Exclusion criteria were the inability to speak and understand the German language and severe acute medical conditions.
All participants received a random pseudonym prior to the data collection. Participants could choose the date of the training according to personal preference. After the appointments had been made, it was decided by lot which training was to take place at which date.
For baseline examination, an anamnesis and physical examination was performed. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [20, 21] was raised as well as the eight-item Patient Health Questionnaire scale (PHQ-8) for depressive symptoms [22, 23]. Before (T0) and after (T1) the training the participants filled out a questionnaire for pain-specific self-efficacy and two knowledge questionnaires for disease-specific knowledge. Patient knowledge was measured by the Patient Knowledge questionnaire- Osteoarthritis (PKQ-OA) , which we translated into German for this study using the Beaton method . A translation was carried out in six steps. These steps were: translation, cross-translation, evaluation of semantic equivalence, elaboration of synthesis versions as well as pre-testing in the target population and finally the development of a final version . As a second questionnaire to test disease-specific knowledge, we developed a 16-item multiple-choice questionnaire, the MF-KWA in German (Münchner Fragebogen für krankheitsspezifisches Wissen bei Arthrose, Munich Questionnaire for Disease-Specific Knowledge Osteoarthritis).
For the examination of pain self-efficacy, the German Adoption of the Pain Self-Efficacy Questionnaire PSEQ , called FESS (Fragebogen zur Erfassung der schmerzspezifischen Selbstwirksamkeit), was used .
After the intervention, the participants were asked to fill out the comprehensibility of health education programs questionnaire (COHEP) a 30 item to assess patient-perceived comprehensibility of health education programs. The questionnaire comprises four scales, the trainer scale (11 items), the transferability scale (9 items), the medical information scale (6 items) and the amount scale (4 items) .
16 weeks after the classroom session (T2), WOMAC, PHQ-8, PKQ-OA, MF-KWA and FESS were collected again.
In both trainings, the same disease-specific knowledge was imparted, only the motivational psychological coaching elements differed in the groups. The knowledge units consisted of anatomy, pathophysiology and therapeutic options. The participants could ask individual questions at any time. Group A received a HAPA-based training. Participants were supported in developing risk awareness, reflecting on their previous experiences of physical activity with the corresponding barriers in its implementation and finally developing individual goals with concrete action plans.
For the development of training B, a group of physicians with neurological, orthopaedic and rehabilitative background as well as experienced psychologist, psychotherapists and physiotherapists, who all had prior teaching and patient education experience, was formed. These experts designed an image-based intervention. Twenty-five photos of animals and landscapes were compiled. Among the pictures were, for example, images of hiking trails, meadows, bridges, hills, and animals that were often in motion. Each participant was asked to choose a favourite picture and use it to formulate a positive feeling associated with better management of their OA. The favourite picture was given to the patients after the intervention as a coloured print, and the participants wrote the individual feeling associated with it by hand on pre-designed cards, similar to greeting cards with sayings.
Both training courses took place as group classroom sessions with a duration of about 120 minutes. The educational trainings for both groups were conducted by the same team consisting of a physician specialized in rehabilitation and a physiotherapist.
A sample size calculation was performed prior to the study. To achieve a power of 80%, a sample of at least 42 participants was needed to detect medium to large effects, 21 in each group.
Differences of each group between the T0, T1, and T2 were compared using the nonparametric Wilcoxon-signed-rank-test. The comparison between training group A and training group B was performed using Mann-Whitney-U tests.
For statistical calculations, the software package IBM SPSS Statistics 26.0 was used.