arthritis
Concise Oxford English Dictionary © 2008 Oxford University Press:
arthritis /ɑːˈθrʌɪtɪs/
▶noun a disease causing painful inflammation and stiffness of the joints.
– derivatives
arthritic adjective & noun.
arthritic adjective & noun.
– origin C16 (earlier (ME) as arthritic): via L. from Gk, from arthron ‘joint’.
'arthritis' also found in these Oxford entries:

