Reinforcement of Placebo Response in Knee Osteoarthritis: A Randomised Trial

Reinforcement of Placebo Response in Knee Osteoarthritis: A Randomised Trial

Saline intra-articular injections used as placebo treatments have been shown to provide pain relief in knee osteoarthritis (OA) It has further been shown that beneficial effects can be induced merely by having a conversation with a health professional.

The aim of this study is to determine whether an individual conversation based on the individual's illness perception related to knee OA affects the response to an intra-articular treatment with saline in individuals with knee OA.

Despite many years of research, there is still considerable uncertainty on what causes placebo effects and how these are mediated. Saline is a pharmacologically inert agent frequently used as placebo comparator in clinical trials of intra-articular (IA) treatments for knee osteoarthritis (OA) and patients often experience a significant pain improvement from this treatment even when it is administered as an open label placebo treatment.

It has further been shown that beneficial effects can be induced merely by having a conversation with a health professional and several studies have found the alliance between therapist and patient to have a positive effect on treatment outcome in physical rehabilitation indicating that positive attention by itself leads to beneficial treatment outcomes. Still it is unclear wether the effect of an open label placebo treatment can be influenced by a conversation and if the extent of this infleuence depends on the focus of the conversation.

The aim of this study is to determine whether a conversation about the individual's illness perception related to knee OA affects the response to a placebo treatment (saline injection) in individuals with knee OA.

Inclusion Criteria:

• Age ≥50 years
• A clinical diagnosis of tibiofemoral OA in the target knee according to the American College of Rheumatology
• Average knee pain in the last week during weight bearing activities of at least 4 on a 0 to 10 points scale (0=no pain; 10=worst possible pain).

Exclusion Criteria:

• Not able to speak or understand Danish
• Scheduled surgery during study participation
• History of target knee surgery within 12 months
• History of arthroplasty in the target knee
• Injection therapy in either knee within 3 months
• Current use of oral glucocorticoids
• Current use of synthetic or non-synthetic opioids
• Contraindications to intra-articular injections, such as wounds or skin rash over injection site.
• Planning to start or discontinue other treatment for knee OA in the study participation period
• Inflammatory arthritis, such as rheumatoid arthritis or psoriatic arthritis.
• Regional pain syndromes
• Generalised pain syndromes such as fibromyalgia
• Lumbar or cervical nerve root compression syndromes
• Any other condition or impairment that, in the opinion of the investigator, makes a potential participant unsuitable for participation or which obstruct participation, such as large knee joint effusion, uncontrolled diabetes, psychiatric and/or neurological disorders, or opiate dependency