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What is The operative procedure is known as "microfracture" is done for the - and explain in detail?
Microfracture surgery

Microfracture surgery is one of the articular cartilage repair surgical techniques that works by creating tiny fractures in the underlying bone.
This cause new cartilage to develop a so-called super-clot.
The surgery is performed by arthroscopy and in the area of the osteochondral defect, tiny fractures are created in the subchondral bone.
Blood and bone marrow (which contains stem cells) seep out of the fractures, creating a blood clot that releases cartilage-building cells.

Note: Osteochondral defect means there is a loss of cartilage along with subchondral bone from a small area of a joint.