The role of osteoprotegerin (OPG) and estrogen receptor (ER-α) gene polymorphisms in rheumatoid arthritis.

Objective. Osteoclast activation at the cartilage pannus junction is an essential step in the destruction of bone matrix in patients affected by rheumatoid arthritis (RA). Receptor activator of NFkappaB ligand (RANK-L) is responsible for osteoclast differentiation and activation.