Chondromalacia means 'softening of the gristle or joint cartilage' and usually refers to the kneecap (patella). The softening can be felt with a blunt probe during surgery.
It is not a diagnosis as such but rather a physical condition, i.e. there is softening of the joint cartilage, and it may be initiated by a number of different disorders with different causes. It is simply a stage in joint surface damage.