auxerat articulos macies, genuumque tumebat / orbis, et immodico prodibant tubere tali. Ov. Met. VIII 807-8.
"Thiness had increased her limbs, and the balls of her knees swelled, and they jutted out with such disproportionate swelling".
EVERY translation I've looked at takes "ankle-joints" as the subject of prodibant. Where did they get that from?