Because my legs haven't disabled me, if anything they've enabled me.
The sentence as it stands it either entirely ungrammatical or else it adopts the colloquialism of starting a new sentence with "because" that had a pretty long statement preceding it.
Example of this construction:
I don't need to listen to my parents. Because I'm a 15-year-old knowitall.
It's often seen in editorials, but it's not proper.
Also, you have two separate thoughts in play. Since1 they are closely related, this type of construction usually has a semicolon separating them.
My legs haven't disabled me; if anything, they've enabled me.
1 I was tempted to use "because" here, though it's grammatically distinct from the because I mentioned above.