Table 1

Outcome measures

Characteristics and confounders	Description and instrument	Data source	Sample	Collection points
Patient’s characteristics	Date of birth, gender, ethnicity, BMI (height, weight), site (s) of OA diagnosis, date of first OA diagnosis, labour situation (working, retired, unemployed, in rehabilitation status)	SAQ, IDB	IG, CO	t0, t3, t6, t12, t24
Primary outcome measure	Clinical outcomes
Pain	WOMAC Index 3.1 German (11-box NRS): subscale pain	SAQ	IG, CO	t0, t3
Function	WOMAC Index 3.1 German (11-box NRS): subscale physical functioning	SAQ	IG, CO	t0, t3
Secondary outcome measures	Clinical outcomes		IG, CO
Stiffness, disease specific impairment	WOMAC Index 3.1 German (11-box NRS): subscale stiffness, overall score	SAQ	IG, CO	t0, t3, t6, t12, t24
Pain, physical function	WOMAC Index 3.1 German (11-box NRS): subscale pain, subscale physical function	SAQ	IG, CO	t6, t12, t24
Health-related quality of life	VR-12 including VR-6D utility index (4-week time slot)	SAQ	IG, CO	t0, t3, t6, t12, t24
General self-efficacy	General Self-Efficacy Scale	SAQ	IG, CO	t0, t3, t6, t12, t24
Response to exercise	OMERACT-OARSI set of responder criteria: composite score with minimum absolute and relative change levels for pain or pain and function	SAQ	IG, CO	t0, t3, t6, t12, t24
Physical activity status	Habitual physical and sports activity status	SAQ	IG, CO	t0, t3, t6, t12, t24
Time to surgery	Endpoint ‘elective joint replacement’	IDB	IG, CO	t0, t3, t6, t12, t24
	Patient satisfaction
Patient satisfaction	Modified version of the ZUF-8 Questionnaire to assess patient satisfaction	SAQ	IG	t3, t6
	Functional performance measures
Knee extension/flexion Hip abduction/adduction Trunk flexion/extension Closed kinetic chain leg extension	Isometric peak torque (1 RPM) using weight machines.	PPT	IG	t0, t3, t6
	Economic data
Unspecific and specific (OA related) healthcare costs	Outpatient costs, hospital costs, costs related to drugs, adjuvants and physical modalities, rehabilitation costs, sick pay	IDB	IG, CO	tm24, tm18, tm12, tm6 t0, t3, t6, t12, t24
Unspecific/specific (OA related) periods of disability	Days of disability (overall and related to OA)	IDB	IG, CO	tm24, tm18, tm12, tm6 t0, t3, t6, t12, t24
Intervention-related costs	Costs for human and physical resources/session	IDB	IG	t3, t6, t12, t24
	Adherence to exercise
Training adherence	Summarised number of attended training sessions according to training log	SAQ	IG	t3
	Safety evaluation
Adverse events and side effects	Summarised number and details of adverse events and side effects according to training log	SAQ	IG	t3

Data source: self-administered questionnaire via mail (SAQ), physical performance test at study site (PPT) and insurance database (IDB). Sample: participants (IG), matched pairs control (CO).
BMI, body mass index; OA, osteoarthritis; OARSI, Osteoarthritis Research Society International; OMERACT, Outcome Measures in Rheumatoid Arthritis Clinical Trials; VR-12, Veterans RAND 12 Item Health Survey; WOMAC Index, Western Ontario McMaster Universities Osteoarthritis Index.