EXercise as TReatment for osteoArthritis

KOOS is a validated and extensively used self-reported outcome measure for people with knee OA. KOOS consists of five subscales, of which the subscale KOOS-ADL will be the primary outcome for this study. KOOS-ADL consists of 17 questions, which are answered on a 4-point likert scale (0=no problems, 4=extreme problems). KOOS-ADL has demonstrated a test-retest reliability (ICC) of 0.84-0.94 as well as demonstrating responsiveness to change following physical therapy in knee osteoarthritis.

Knee extensor muscle power (force times acceleration) will be measured using the Nottingham Power Rig (NPR). The NPR measures the power output in total watt and watt pr. bodyweight in kilograms from a seated push on a flat pedal which is transmitted by a lever and chain to spin a flywheel. The NPR is a safe and reliable method to measure explosive knee extensor muscle power and has been validated as a clinically important measure of muscle function in elderly individuals.

Assessment of functional performance involves time (in seconds) taken to complete a 40 m course at fast walking pace as well as time taken to negotiate 9 steps on a standard step-height stair-way. The tests are part of the recommended functional performance tests in knee osteoarthritis.

Assessment of pain medication intake specific for knee pain. Derived as part of self-reported outcome measure.

The four remaining subscales of the validated KOOS questionnaire (see primary outcome for further info on KOOS). The 4 remaining subscales cover: symptoms, pain, sport & recreation and quality of life.

Continous registration of health issues and injuries. Physiotherapists in charge of the training sessions will monitor potential AE and SAE. Also, during the follow-up visits at week 6 and week 12, the participants will be asked about potential AE's and SAE's using open-probe questions. Finally, the 12 month follow-up will include questions regarding AE's and SAE's during the preceding period from baseline to 12 months.

Pan sensitization will be assessed through pain pressure cuff algometry (PPCA). The assessment involves placing a pneumatic pressure cuff with automatic inflation around the participant's lower leg. Through four different tests, the participant is asked to rate pain intensity (VAS). The pain scores along with cuff pressure (kPa) is registered. The PPCA is an increasingly used measure of deep-tissue pain sensitization, which allows for multimodal measurements of pain mechanisms in the knee-OA population.

In order to assess morphologic changes and changes in muscle quality of the knee extensors, patients will undergo two MRI scans (baseline & follow-up). MRI is considered the gold standard in assessing morphometric muscle changes in humans.

Isokinetic dynamometry will be conducted in order to assess the contractile properties of the knee extensors. The dynamometry assessments will allow for specific strength evaluations and is a validated measure of maximal contractile muscle strength.

The 30 sec chair-rise (total reps) is part of the recommended functional performance tests in knee OA.

VAS will be derived for the questions: last 24 hours, last week and after 30 min. of walking.

WPI will be assessed by questions on regional body pain as validated by the American College of Rheumatology.

NRS will be derived before, during and after each exercise session as well as before and after each testing procedure. The NRS assessments will allow for an evaluation of the effects of exercise and functional activities on self-reported pain ratings.

Patient reported physical activity levels.

The number of exercise sessions that the patient participates in out of the total 24 supervised sessions.

Self-reported assessment at baseline, 6 and 12 weeks and at 12 months.

A self-reported outcome measure of health-related quality of life, covering 5 dimensions (movement, personal care, everyday activities, pain/discomfort and anxiety/depression). Is translated and validated for use in a Danish population.

PASS registers how patients perceive their current symptom state. Answered by "yes" or "no" to the question; "When you think of your knee function, will you consider your current condition as satisfying?".

GPE registers how patients perceive the effects of the interventions on a 7-point likert scale.

Only answered by patients answering "no" to PASS. TF registers if the patients perceive the intervention as failed. Answered by "yes" or "no" to the question; "Would you consider your current state as being so unsatisfactory that you consider the treatment to have failed?".