(Chapter 4) Footnote 17:

Vesalius cites Hippocrates’ De articulis, where the verbal cognate a)ph/rqrwtai “is articulated [by aparthrosis]” is used of the temporomandibular joint (30.12); the noun appears only in Galen’s commentary on it, 18a.433.6. The term “diarthrosis” is applied in modern anatomy to synovial joints, where hyaline tissue, synovial fluid, and a synovial membrane intervene between the bony surfaces.