Which morphologies of synovial folds result from degeneration and/or aging of the radiohumeral joint: an anatomic study with cadavers and embryos.

The synovial folds of the radiohumeral joints in cadaveric elbows from 179 elderly subjects and 40 embryos were investigated macroscopically and histologically to determine any morphologic changes caused by aging or degeneration. The anterior and posterior folds found in the elderly population shared characteristics of folds seen in embryos, with some modifications, and were thought to originate from the primitive septum. Proportionally, the length, width, and thickness of these folds were consistent between adults and embryos. However, the embryonic folds showed a homogenous morphology. In contrast, in the adult the anterior fold was characterized by a shorter and narrower villous pattern, and the posterior fold tended to be wider. Lateral extension of the anterior or posterior folds was also observed. Moreover, the lateral fold, never seen in embryos, was present and characterized by a hard plicate pattern in the adult. These derived or specific morphologies in adults probably result from alterations in the movement of the radial head caused by aging.