Inflammation in osteoarthritis: the latest progress and ongoing challenges

Area of Science:

• Immunology
• Rheumatology
• Cell Biology

Background:

• Osteoarthritis (OA) is a chronic degenerative joint disease with complex pathophysiology.
• A growing body of evidence suggests inflammation, particularly synovitis, plays a critical role in OA, potentially explaining the disconnect between radiographic changes and patient symptoms.
• Understanding the inflammatory mechanisms in OA is crucial for developing effective therapeutic strategies.

Approach:

• This review synthesizes recent (post-2020) basic science, mechanistic, and clinical findings related to inflammation in osteoarthritis.
• It examines the evolving understanding of immune cell involvement, including macrophages, and their interactions in the OA joint.
• The review also considers the impact of biological and environmental factors on OA inflammation.

Key Points:

• Synovitis is a key inflammatory process in OA, potentially explaining symptom variability and disease flares.
• Joint-resident and systemically derived immune cells, especially macrophages, are central to the inflammatory response in OA.
• Factors such as exercise, age, and diet influence OA inflammation, with both protective and detrimental effects.

Conclusions:

• Osteoarthritis is fundamentally an inflammatory disease, with immune cell crosstalk driving pathology.
• Despite advances in understanding OA inflammation, there is a lack of disease-modifying treatments targeting these inflammatory pathways.
• Further research is needed to bridge the gap between understanding OA inflammation and developing targeted therapies.