Kneeitis

A Kerryman was suffering from pains in his knees, so he visited the doctor.
'You're suffering from a disease that we medical experts call "kneeitis",' said the doctor. 'Take it easy for a month or so and above all don't climb any stairs. That puts a terrible strain on the knees'. A month later the Kerryman returned and after a brief examination was found to have recovered completely.
'Can I climb the stairs now doctor?'
'Certainly', replied the doctor.
'Thank Heavens', said the Kerryman, 'I was getting a bit browned off climbing up the drainpipe every time I wanted to go to the toilet'.