Longman Dictionary of Contemporary English
The Collaborative International Dictionary
knock-kneed \knock"-kneed`\, a. Having the legs bent inward so that the knees touch in walking. [Written also knack-kneed.]
Wiktionary
a. 1 (context of the legs English) having the knees abnormally close together, and the ankles spread apart 2 (context of a person or animal English) suffering from genu valgum (or tibia valga)
WordNet
adj. having the knees abnormally close together and the ankles wide apart
Usage examples of "knock-kneed".
Brittany stares at her for a moment, and then the youngest of the ultra-rads charges at her, whooping and flailing his arms, and she squeals and runs from him with a knock-kneed gait, floundering up the powdery white slope of a dune with the boy scampering alongside.
To the left Schalke-North with Wilhelmine-Victoria Mine, to the right Wanne without Eickel, past the Emscher marshes Gelsenkirchen stops, and here, which is where the branch line with its rusty rails and weeds was headed, there lies, silenced and half destroyed by bombs beneath an old-fashioned knock-kneed headfrarne, that Pluto Mine which has given Pluto, the black shepherd male, his name.
At the rear it tended towards a slight cow-hocked stance, which in humans was called knock-kneed.