

山を下りるとき、膝が痛くなりました。
祖母は膝が悪いので、長く歩けません。
正座をしていて、膝がつらくないですか?
"ひざ(膝)" is in the lesson "Body parts 2" (Level 25), along with 8 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.