Metatarsophalangeal joints
The metatarsophalangeal joints (MTP joints) are the joints between the metatarsal bones of the foot and the proximal bones (proximal phalanges) of the toes. They are analogous to the knuckles of the hand, and are consequently known as toe knuckles in common speech.
Source: Wikipedia — Metatarsophalangeal joints (CC BY-SA 4.0)