The Collaborative International Dictionary
Housemaid's knee
Housemaid \House"maid`\, n. A female servant employed to do housework, esp. to take care of the rooms.
Housemaid's knee (Med.), a swelling over the knee, due to an enlargement of the bursa in the front of the kneepan; -- so called because frequently occurring in servant girls who work upon their knees.
Wiktionary
housemaid's knee
n. Swelling of the bursa before the kneecap.
WordNet
housemaid's knee
n. swelling of the bursa in the knee (due to trauma or excessive kneeling)
Usage examples of "housemaid's knee".
Personal sacrifice netted these women nothing except, perhaps, a case of housemaid's knee.
She was a gaunt, grayish-blond middle-aged woman, but she moved quite rapidly in spite of her case of housemaid's knee.