P2RX7 and osteoarthritis: Purinergic receptors can be divided into two major categories, P1 and P2 receptors, and it has been demonstrated that electromagnetic fields can upregulate the expression of Adenosine Receptors, with significant upregulation of A2A and A3, exerting similar effects as adenosine receptor agonists, and can downregulate PGE(2) levels to achieve control of osteoarthritis [85, 86].