NPY and rheumatoid arthritis: The results of our study were in agreement with the available clinical literature, which has also found significantly higher concentrations of NPY in the synovial fluid of patients with arthritis of the knee (crystal induced arthritis, chronic polyarthritis, post-infectious arthritis, rheumatoid arthritis), compared to control patients with non-inflammatory joint disorders (lateral meniscus injury, medial meniscus injury, cruciate ligament injury), admitted for arthroscopy [40, 41].