Inclusion Criteria:  Age 18 or more A clinical and radiological diagnosis of knee OA BMI ≥ 30 kg/m2 Motivated for weight loss as by the provided program Signed informed consent.  Exclusion Criteria:  The scheduled surgery is for revision of an existing prosthesis Planned surgery for more than one knee within the observation period KA indication due to sequelae of fracture(s) Injection of medication or substances in the target knee within 3 months prior to participation Immuno-inflammatory arthritis as cause of the knee OA Current systemic treatment with glucocorticoids equivalent to > 7.5 mg of prednisolone/day Previous or planned obesity surgery Inability to understand or read Danish incl. instructions and questionnaires Any other condition or impairment that, in the opinion of the investigator (or his/her delegate), makes a potential participant unsuitable for participation or which obstruct participation.