os ‧ te ‧ o ‧ ar ‧ thri ‧ tis /ˌɒstiəʊɑːˈθraɪtəs, ˌɒstiəʊɑːˈθraɪtɪs $ ˌɑːstioʊɑːr-/ BrE AmE noun [uncountable]
a medical condition which makes your knees and other joints stiff and painful
os ‧ te ‧ o ‧ ar ‧ thri ‧ tis /ˌɒstiəʊɑːˈθraɪtəs, ˌɒstiəʊɑːˈθraɪtɪs $ ˌɑːstioʊɑːr-/ BrE AmE noun [uncountable]
a medical condition which makes your knees and other joints stiff and painful
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012