Ankylosing spondylitis in the wrists, forearms, and spinal column
Note the fused wrist bones in the arms, and the abnormal protuberances, fusions, and cavities in the spine.
Ankylosing spondylitis (also known as Bechterew’s disease) is an inflammatory spondyloarthropathy (arthritis affecting the spinal column), and its name comes from the Greek “ankylos-”, meaning “crooked”. Spondylitis can be broken down into “spondyl-” and “-itis”, which mean “spine” and “inflammation”, respectively.
Simply put, it’s a fusion of the joints in the axial skeleton (the spinal column, ribcage, and cervical collar), but there’s little else that’s simple about this condition. While it’s known to have a strong genetic predisposition and heritability, the exact triggers that begin the process of syndesmophytosis (literally "the process of abnormal binding together") which fuse bones together is not known.
While many of the genetic and immune factors in AS similar to those in rheumatoid arthritis, ankylosing spondylopathy has been differentiated from other RA conditions as early as the second century CE, by Galen. Because of its effect on the spinal column, AS has long been known as "bamboo spine".
Unfortunately, despite many treatments and therapies being available to counteract the effects of this autoimmune condition on the bones and organs, there is no cure.
Observations on the hip joint: to which are added … other similar complaints. Edward Ford, 1810.