how is muscle degeneration different from necrosis?

Muscle degeneration is a wasting of muscle tissue. Necrosis is dying tissue. The first can be slowed with physical therapy. Necrosis, I don't know.

(c/p) https://www.google.com/search?q=how+is+muscle+dege...

I had no idea so I googled your question & this is the results of that search.

If this is about you & not a dog, so another google search for humans.  This is the dog section under PETS.

Degeneration is essentially the muscle tissue wasting away.

Necrosis is tissue death.

Whether or not they are recoverable will depend on cause and how soon treatment is given.   Necrosis often entails removal of the dead tissue and antibiotics to prevent septicemia.

Degeneration may or may not be treatable, depending on the cause

Degeneration and necrosis represent a continuum of lesions and therefore are often both present within a given lesion. Due to the limited repertoire of skeletal muscle responses, they share similar morphologic features and can thus be difficult to differentiate histologically.