Source : Webster's Revised Unabridged Dictionary (1913)

Knock-knee \Knock"-knee`\, n. (Med.)
   A condition in which the knees are bent in so as to touch
   each other in walking; inknee.

Source : WordNet®

knock-knee
     n : inward slant of the thigh [syn: {genu valgum}, {tibia valga}]