Osteoarthritis (OA) is a condition affecting the whole joint and is a major cause of pain and disability worldwide. Although OA is very common, the initial steps which lead to the development of pain and tissue damage are not fully understood. In this study participants will be investigated for markers in the blood, joint and urine in people who have a diagnosis of osteoarthritis or inflammatory arthritis and are receiving a steroid injection for their condition. Markers will be evaluated in participants with osteoarthritis compared with other types of arthritis, including rheumatoid arthritis and spondyloarthritis.

Osteoarthritis (OA) is the most common form of arthritis worldwide. OA causes major disability and pain and places a huge financial burden on healthcare worldwide. In recent work, the gene expression profile of bone marrow lesions (BML) in osteoarthritis has been evaluated. BML in OA have a novel gene expression profile which includes genes involved in inflammation, neurogenesis and matrix turnover. The plan is to investigate the functional significance of the genes found at the protein biomarker level in studies of joint tissue, blood and urine from participants with knee OA and compare these changes with participants who have other forms of arthritis, including rheumatoid arthritis and spondyloarthritis.

A study amendment was added in April 2020 due to Covid-19. We are studying up to 150 additional participants with or without inflammatory conditions who are being treated with immunomodulatory drugs compared with participants who are not on immunomodulators. We will be evaluating the course of Covid-19 infection in people without autoimmune inflammatory conditions, compared with people who have autoimmune inflammatory diseases who are on immunomodulators.

Inclusion Criteria:

Inclusion Criteria for OA patients:

• Fulfilling the American College of Rheumatology (ACR) criteria for the diagnosis of knee osteoarthritis
• Symptomatic knee pain
• On usual care for knee osteoarthritis including paracetamol and/or NSAIDs

Inclusion criteria for Inflammatory Arthritis Patients:

• Fulfilling the American College of Rheumatology (ACR) criteria for the diagnosis of inflammatory arthritis i.e. rheumatoid arthritis (Anti-CCP antibodies & Rheumatoid Factor checked ), psoriatic arthritis or spondyloarthropathy
• Symptomatic knee pain
• On usual care for arthritis including disease-modifying anti-rheumatic drugs (DMARDs), paracetamol and/or NSAIDs

Exclusion Criteria:

• Other rheumatological diagnosis e.g. systemic lupus erythematosus, fibromyalgia, Polymyalgia Rheumatica, Gout, Giant Cell Arteritis, Sjogren's syndrome
• History of uncontrolled depression
• Recent surgery
• Uncontrolled ischaemic heart disease
• Uncontrolled diabetes mellitus
• Alcohol consumption > 14 units/week as per UK National guidelines
• Participants unable to give full informed consent

The study population includes participants with an established diagnosis of knee osteoarthritis, rheumatoid arthritis, spondyloarthritis or psoriatic arthritis. A control group without arthritis or knee pain serves as the comparator group

All data will be published and open access after completion of the study.