The investigators will recruit two groups of patients with OA-related knee pain from hospital clinics, (i) those with moderate-severe knee pain who have not yet had a TKR and (ii) those who have had a TKR who have persistent pain after one-year. All participants will complete baseline assessments before commencing an eight-week group based programme of Mindfulness training, delivered by an NHS physiotherapist who is also a trained Mindfulness teacher. Participants will have daily meditation practices to carry out at home. Follow-up questionnaires will be repeated after the intervention and again at 6 months.