The toes of the human body consist of phalanges, which are the bones found in the distal (front-end) foot. When two bones connect, it is referred to as a joint. The interphalangeal articulations are the joints formed in between two phalanges. The collateral ligament of interphalangeal articulations of foot refers to the ligaments directly on top of the joints, which give the joints flexibility and movement. (Ligaments are fibrous connective tissue that usually join bones.)
Each articulation, or joint, has two collateral ligaments. On top of the ligament is an extensor tendon. The tendons connect the bones to muscles found in the foot. The purpose of the tendon is to allow extension of the foot bones. The first and second joints are more flexible and extend more than the other toe joints.
The collateral ligament of interphalangeal articulations of foot determines, or limits, the amount of flexibility in the toes. When the ligament tightens, due to strain, stress, or pressure on the foot, it keeps the toes from flexing and extending properly.