He attacks your ankles because he is too old and stiff to reach any higher.
My Frankie attacks my feet if they pop out from under the duvet during the night. He must sit there all night waiting for my feet to encroach into his attack zone.
My cat is 18 and still regularly jumps onto and over a six foot fence when he can smell salmon cooking in the next door house, he knows there is always a bit left for him . He also chases seagulls that come into the garden (without success I may add) so Velvetee ,old cats can, and do lead a very active lives.