Diffuse Idiopathic Skeletal Hyperostosis, or DISH (a.k.a. Forestier's disease) was first described over 100 years ago, It affects from 2.5% to 10% of people over the age of 70.
It causes inflammation, and bone overgrowth, at the sites where tendons are attached to bones. It typically affects the spinal vertebrae, but can also affect any other bone, e.g. the neck, shoulders, ribs, hips, pelvis, knees, ankles, and hands. where it leads to stiffness and painful movements.
The cause is unknown.
It's usually diagnosed via X-Ray, and is treated with analgesics and non-steroidal anti-inflammatory drugs. Unfortunately, the drug treatments do not reverse the condition.
For technical details see : Medicine 76(2):104-117
Also see : Ankylosing Spondylitisplugin-autotooltip__plain plugin-autotooltip_bigAnkylosing Spondylitis
"Ankylosing spondylitis (AS) is a type of arthritis that affects the spine. AS often involves redness, heat, swelling, and pain in the spine or in the joint where the bottom of the spine (sacrum) joins the pelvic bone (ilium)."