MBP and rheumatoid arthritis: D’Agostino et al. evaluated entheses of 164 patients with a spondyloarthropathy, 34 with mechanical back pain (MBP) and 30 with rheumatoid arthritis (RA); vascularization at the enthesis was found in 81% of spondyloarthropathy patients but in none of the patients with MBP or RA [100].