Sentence:  The <WSD>patellae</WSD> may be up to 30° externally rotated at birth. In young children it is considered normal for the <WSD>patellae</WSD> to be externally rotated, but by 5 years of age the <WSD>patellae</WSD> should face forwards. 
Meaning of the word marked with <WSD> tags:  The sesamoid bone of the knee; the kneecap.