The real-life Agnes Tachyon had a torn tendon that healed back wrong (i.e. "bowed tendon"), ending his racing career permanently and prematurely.

(Genetics may also be a factor, as foals sired by Agnes Tachyon also have a tendency to have leg problems.)

IIRC the umamusume Agnes Tachyon is also implied to have some sort of degenerative disease in her legs (which becomes her central motivation for all her 'mad scientist' habits trying to research a cure), though this might be one of the retired retgoned snippets.

-Scientists who can't cure their own disease
-Test their works into others
-Very chaotic

So why is Caustic a horse girl?

NNescio said:

The real-life Agnes Tachyon had a torn tendon that healed back wrong (i.e. "bowed tendon"), ending his racing career permanently and prematurely.

(Genetics may also be a factor, as foals sired by Agnes Tachyon also have a tendency to have leg problems.)

IIRC the umamusume Agnes Tachyon is also implied to have some sort of degenerative disease in her legs (which becomes her central motivation for all her 'mad scientist' habits trying to research a cure), though this might be one of the retired retgoned snippets.

Pretty sure that in-game Tachyon still talks about her disease. So yeah, it's still relevant.