Feasibility of an Early Home-based Cycling Intervention After Knee Arthroplasty

The goal of this pilot clinical trial is to evaluate whether an early, home-based stationary cycling programme, provided in addition to standard postoperative home exercises, is feasible and acceptable for patients recovering from knee arthroplasty. It will also inform the design of a larger clinical trial examining the effects of adding early cycling to standard postoperative home exercises on postoperative outcomes. The main questions it aims to answer are: * Can the cycling programme and planned study procedures be delivered as intended? * Are participants willing and able to take part in the study and follow the planned interventions? * Do participants find the cycling programme and outcome assessments acceptable? * What changes, if any, are needed before conducting a larger clinical trial? Researchers will compare an early home-based stationary cycling programme provided in addition to standard postoperative home exercises with standard postoperative home exercises alone. Participants will: * Be randomly assigned to either the cycling group or the standard exercise group (control group) two weeks after surgery. * If assigned to the cycling group, perform 30 minutes of stationary cycling at home at least five days per week for eight weeks in addition to the standard postoperative home exercise programme. * If assigned to the control group, follow the standard postoperative home exercise programme and refrain from structured cycling during the eight-week intervention period. * Complete questionnaires and physical assessments at baseline and follow-up visits. * Complete selected patient-reported outcome measures at 6 and 12 months after surgery.

Inclusion Criteria: * Scheduled for unilateral primary medial unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA). * Age ≥ 18 years. * Able to speak and read Danish. * Daily access to a stationary bike during the intervention period, or willingness to use a stationary bike provided by the study through an external rental company for the duration of the intervention. Due to logistical constraints, loan bikes can only be provided to participants residing within approximately one hour of transport from Aarhus or Silkeborg. Participants living outside this area may participate if they have access to a stationary bike. * Ability to use a smartphone with internet connectivity (required for completion of electronic questionnaires and using SENS motion application) or a tablet and having an email address enabling completion of electronic questionnaires. Exclusion Criteria: * Previous surgery in either lower limb within 3 months before the date of knee arthroplasty or planned surgery in either lower limb within 3 months after the date of knee arthroplasty. * Inflammatory joint disease * Previous osteotomy around the knee or tibial condyle fracture that has been treated with osteosynthesis in the affected knee. * Medical or physical conditions that would prevent safe participation in the cycling intervention (e.g., unstable cardiovascular, pulmonary, or chronic neurodegenerative disorders). * Active cancer treatment, if this treatment would interfere with safe participation or adherence to the cycling protocol. * Preoperative reduced knee flexion preventing full pedal rotation on a stationary bike. * Current or recent history of alcohol and/or substance misuse, as identified during the anaesthetic pre-assessment and documented in the electronic patient record. * Cognitive impairment (e.g. dementia) or diagnosed psychiatric disorder that would prevent the patient from understanding or adhering to the cycling protocol.