We recruited physical therapists using the database of clinical cooperation partners of the University of Applied Health Sciences (Bochum) and through personal networks. To be eligible, physical therapists needed to be registered physical therapists (have a degree in physical therapy) and work in an outpatient physical therapy setting. Furthermore, they needed to have at least 5 years of experience in treating patients with hip or knee OA, give informed consent, be able to understand and speak German, have access to the internet, and own a digital device (eg, tablet, smartphone, or laptop).

Participating physical therapists were asked to contact eligible patients with OA and sent them an information letter regarding the study. Furthermore, patients were recruited through personal networks (eg, via patient associations). Inclusion criteria for the patients were medically diagnosed idiopathic OA of the knee or the hip and signed informed consent. Further criteria were to be able to understand and speak German, have received at least one prescription for physical therapy regarding their OA-related symptoms, own a digital device (eg, tablet, smartphone, or laptop), and have internet access.

The aim was to recruit both physical therapists and patients who already had experience with digital health care in any context, as well as physical therapists and patients who did not have this experience. Participants were recruited until saturation was reached, which was when no new information would be identified from the last two interviews [20]. Theoretical sampling was used [21].

To obtain a broad distribution of participants, we aimed to recruit a member of a patient association, an owner of a physiotherapeutic practice, a physician, a politician in the field of health care, a person of a health insurance company, a representative of a company developing digital devices, and a member of a physical therapy association. We recruited these stakeholders through patient associations, assisted by a German physical therapy association and through personal networks. To be eligible, participants needed to have at least 5 years of professional experience in their field, internet access, own a digital device (eg, tablet, smartphone, or laptop), give signed informed consent, and have sufficient skills in German.

The inclusion and exclusion criteria were screened via telephone before study participation for all participants.

Two researchers (AA and FW) transcribed verbatim and coded the transcripts of the interviews. Data analysis of the interviews was performed based on the framework approach [26]. Using explorative data analysis for each main topic from the interview scheme, citations were extracted and arranged into themes and subthemes. Subsequently, these themes were discussed between the researchers (AA, FW) until consensus was reached; the complete list of themes and subthemes is presented in Multimedia Appendix 2. Finally, all codes of each theme of every participant were displayed in a table [27]. Next, one researcher (FW) examined the raw data again to ensure the robustness of the analytical process and to confirm that all data were indeed reflected in the coding. Transcription, coding, organization, and analysis were performed using MAXQDA Plus 2020, Windows version 20.3.0.

Data from round one were exported from the secure online platform into an Excel sheet. Demographics, data from the (digital) health literacy questionnaires, as well as data from the online questionnaire were analyzed descriptively with SPSS (IBM SPSS Statistics 25). Results were analyzed by quantifying scores on each item from the questionnaire and calculating percentages of patients and physical therapists who chose a certain answer on the items.

In round two, focus groups were recorded in writing protocols. Data were categorized into the corresponding themes or subthemes of the interviews according to the CFIR domains. Categorization was discussed between two researchers (CG and FW) until consensus was reached. Data were screened regarding repetitions and each theme and corresponding subthemes were summarized.

A changing role of physical therapists was a central precondition for blended care, which received consensus of physical therapists and stakeholders. Different facets of changes have been mentioned; however, the main adjustment was seen in the patient-provider relationship. According to physical therapists, both should be on an equal level with the physical therapist being in a guiding role. There was a full consensus of the physical therapists that blended care has an essential impact to facilitate a patient’s self-management and individual responsibility.

Patients also considered a healthy relationship with and trust in the physical therapist as a crucial precondition for blended care. In contrast to the perspective of physical therapists, passive interventions (and therefore in-person contact) were still one of the most important aspects of physical therapy for patients. Patients were afraid of having less in-person sessions in favor of more digital sessions.

Patients and physical therapists considered adequate communication skills of both groups and a moderate level of health literacy of patients as necessary. From the perspective of physical therapists, a core competence within blended care was the need to be familiar with the technology used. All physical therapists and stakeholders concluded that decision-making is a further competence required if the approach is to be useful and feasible for every patient. As a precondition for using digital health in physical therapy, they mentioned an adequate training of new competences for the physical therapists and gaining positive experiences with digital care for both patients and physical therapists.

All participants mentioned the COVID-19 pandemic as a facilitator for blended care, especially increasing the acceptance of digital care. Most of the physical therapists were open regarding digital care. Patients needed and wanted to learn how to handle digital tools in advance. The acceptance of blended care of patients varied; however, in general, they recognized the convenience to exercise anytime and place and incorporating the therapy into their daily lives. Further preconditions to increase the acceptance of patients were the confidence in the physical therapist and sufficient time to learn and practice.

The vast majority of all participants considered educational components, information exchange, and an exercise program as content that can be carried out digitally. The results of the online questionnaire regarding the preferred mode of delivery are shown in Table 3.

All physical therapists agreed on the importance to integrate motivational strategies in the technology, such as with activity trackers and reminders (Table 4).

Physical therapists perceived the digital program within blended care as a guiding tool, whereas patients saw digital components only as a supplement to regular in-person sessions. The results of the online questionnaire including specific software features and content are presented in Table 4.

Patients and physical therapists had the same opinion regarding the importance of technology being user-friendly. From their perspective, digital tools should be easy and intuitive to use.

All participants agreed that blended care must be tailored to the patients’ individual needs. Participants considered in the online questionnaire an average ratio of 60/40 digital/in-person sessions as optimal (Table 5). Physical therapists and patients considered that a first in-person session is crucial, and that the longer the treatment process, the less in-person sessions are necessary. Stakeholders stated that the needs of the patient, access to devices, state of condition and confidence in physical therapy, motivation of the patient, as well as a high level of patients’ self-management are factors that influence the decision on the most appropriate therapy mode.

An academic education and several years of professional experience as a physical therapist were mentioned as preconditions, since this supports the decision on the therapy mode from the perspective of the stakeholders.

The stakeholders emphasized the value of “taking the physical therapist home,” which would increase the sustainability of therapy in their point of view.

Patients and physical therapists considered a separate room only for digital care (eg, video conference) as necessary to be undisturbed, maintain privacy of the patient, and having all equipment ready to use.

Physical therapists considered a change of practice structures as necessary. Proper time planning is important (eg, to prepare digital sessions). The stated preconditions regarding a practice setting for the usage of blended care are summarized in Table S1 of Multimedia Appendix 3.

A precondition for blended care was that every user has access to digital devices and a stable internet connection. Physical therapists preferred tablets or laptops as hardware. Patients considered missing equipment and technical requirements as a barrier for blended care. They preferred a large screen on their digital devices. The stakeholders stated the importance of the interoperability of different systems, especially with already existing systems.

The interviewed physical therapists expected a facilitation and simplification of the interprofessional communication and cooperation within blended care. For instance, data should be collected and stored in a more structured way and the treating physician would have the option to access the status or progress of the patient; in that way, the communication between the physical therapist and physician will be based on results and data. Further, the transfer of a patient to another physical therapist can be easily achieved.

Stakeholders concluded that time is an advantage but also a disadvantage. For instance, blended care could save time when filling out questionnaires in advance; however, there is more time needed for preparation. All participants were in accordance that the financial reimbursement for blended care needed to be clarified (eg, time for preparation and for the digital care part, costs for licenses and systems). Stakeholders determined that health insurance companies needed to cover the costs for in-person and digital care. Therefore, the single blended care intervention needed to be specified and described well.

Structural preconditions mentioned included legal requirements, proof of effectiveness, data protection, and security. Stakeholders suggested certifications for each type of technology, which meet data protection guidelines. Additionally, physical therapists suggested educating patients regarding data protection and security.

An (advanced) training for physical therapists should particularly focus on digital communication, data protection issues, and evidence-based digital care. Patients should particularly be educated regarding the handling of technology.

Stakeholders concluded that important steps before an implementation of blended care are its communication and promotion, dealing with resistance, training of physical therapists as specialists, and well-prepared introduction of technologies.

Structural facilitators were seen in the COVID-19 pandemic and if patients were provided with digital devices. The competitive market, missing transparency, privacy issues, and different understandings of blended care were considered as structural barriers. All facilitators and barriers regarding blended physical therapy are listed in Figure S1 of Multimedia Appendix 3.