A semi-lunar cartilage is the old-fashioned name for a meniscus. 'Semi-lunar' means 'half-moon' and refers to the shape of the meniscus.

Nomenclature issue
In the sporting world, players and coaches often refer to a tear of their 'cartilage' when they should be saying 'meniscus'. This creates confusion when the white covering of the bones is also known as 'cartilage', and tears of the one are very different from tears of the other.
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FORUM DISCUSSIONS
Looking at options for cartilage replacement
Nightmare after meniscal repair