The mandible is the lower jaw bone of the horse. It is the only movable bone of the skull, articulating with the temporal bone just below and forward of each ear at the temporomandibular joint. All the lower teeth are set into the mandible: incisors at the front, the tushes (canine teeth) in male horses, and the cheek teeth (premolars and molars) running back along each branch.
Structurally, the mandible consists of two halves fused at the chin into a single U-shaped bone. The flat vertical portion of each half is the ramus; it forms the cheek and carries the condyle that fits into the temporomandibular joint. The horizontal body holds the dental arcade. The space between the two sides of the lower jaw, just behind the chin, is the curb groove, where a curb chain or strap rests in certain bitting arrangements.
Width of the mandible at the throat determines how easily a horse can flex at the poll without compressing the airway and parotid gland. A narrow mandible is considered a conformation fault because it limits that flexion. Judges and buyers assess intermandibular width as part of head and throat evaluation.
Dental work, wolf tooth removal, and bit selection all center on the mandible. The temporomandibular joint and mandibular teeth are examined when a horse resists contact or shows head-tilt.