What is an MCHA?
Calcium Microcrystalline Hydroxyapatite (MCHA) is a calcium compound, containing minerals in their natural ratios, as well as residues of matrix, proteins, and glycosaminoglycans. MCHA supports bone mineral composition and can potentially reduce the risk of degenerative joint issues.

That's what I found when I googled. The woman(a nurse practitioner) who recommended this to me did a much better job of explaining it all...I should have taken notes!