Sentence:  Such maladies as osteoarthritis of various joints (spavin in the hocks, ringbone in the pasterns, <WSD>osselets</WSD> in the fetlocks, navicular disease in the heels of the forefeet) are very common, as is chronic lower back soreness (coldback) in the lumbar, sacral, and thoracic regions.Webster 1913 
Meaning of the word marked with <WSD> tags:  A hard substance growing on the inside of a horse's knee.