Osteoarthritis versus rheumatoid arthritis synovial expression of lipoxygenase enzymes. Ostheoarthritis (OA) synovial tissue displays a lower expression of 5-lipoxygenase (5-LO) and 15-LO-1 compared with rheumatoid arthritis (RA) synovium. Graphs show computer assisted-image analysis results for (a) 5-LO and (b) 15-LO-1 expression in RA tissue (n = 6) and OA tissue (n = 5). Results expressed as percentages of the total area of counterstained tissue. Horizontal lines, median values; whiskers, range values. **P < 0.01.