Table I.

Definitions of cases, detection, treatment, and control

	Broad definition	Narrow definition
Case definition	Knee symptoms on few days or more in the past month at time of research assessment clinic visit at baseline and evidence of at least definite osteophytes on plain radiographs of the index knee in either tibiofemoral or patellofemoral joint (equivalent to Kellgren & Lawrence grade 2 or more)	Knee symptoms on most or all days in the past month at time of research assessment clinic visit at baseline and evidence of at least definite osteophytes on plain radiographs of the index knee in either tibiofemoral or patellofemoral joint (equivalent to Kellgren & Lawrence grade 2 or more)
Detection	At least one recorded knee-related musculoskeletal general practice consultations in the 3-year period following baseline OR self-reported recall of knee-related general practice consultation in the 3-year period following baseline	At least one recorded knee-related musculoskeletal general practice consultation, specifically coded as osteoarthritis (Read codes N05 or N06), in the 3-year period following baseline
Treatment	Self-report of having been seen by a physiotherapist or hospital specialist for their knee problem, received a TKR, or receiving at least one of the following recommended6 treatments at baseline AND 18-months AND 3-years: dieting to lose weight (if body mass index ≥ 25 kg/m2), specific knee exercises, paracetamol, oral NSAID (including COX2 inhibitor), oral opioid analgesia, topical analgesics/NSAID, or intra-articular injection)	Self-report of receiving at least one of the following recommended core nonpharmacological treatments at baseline AND 18-months AND 3-years: dieting to lose weight (if body mass index ≥ 25 kg/m2), specific knee exercises
Control	Self-reported characteristic pain intensity in the past 6 months7 of <5 out of 108 at two out of the three measurement points (baseline, 18-months, 3-years)	Self-reported characteristic pain intensity in the past 6 months of <4 out of 109 at two out of the three measurement points (baseline, 18-months, 3-years)