膝蓋骨

1. Origins, structure, and basic meaning

• Structure: 膝蓋骨(しつがいこつ) refers to the kneecap, the bone at the front of the knee.
• Basic usage: This noun specifies the bone when describing its position or an injury.

2. Common pitfalls and similar expressions

• Whole-word reading
  • 膝 has the everyday word reading ひざ, but do not insert that reading into this term: read the whole word 膝蓋骨 as しつがいこつ.
• Not the entire knee
  • 膝 broadly refers to the knee, while 膝蓋骨 is one specific bone.