[32, 33] The Prg4 gene encodes for the protein, lubricin, a critical glycoprotein in synovial joint fluid and cartilage superficial zone that provides joint lubrication.[32] Mice lacking lubricin develop age‐dependent osteoarthritis‐like degeneration in joints, such as TMJs and knees.[32, 33, 43] We first confirmed the joint degeneration in Prg4‐/‐ mice through traditional hematoxylin and eosin (H&E) staining. The gene discussed is PRG4; the disease is osteoarthritis.