Weak, feeble.

Of living beings (and their attributes): Wasted or worn out with old age, decayed and enfeebled with infirmities; old and feeble.

Not strong; feeble, weak.

Exhibiting the weakness of old age.

figurative. Worn out, esp. with age; creaky, ageing, deteriorating; slow or halting. Also: having the appearance of joints affected with arthritis…