# Locking of the jaw joint (TMJ closed lock)
The temporomandibular joint is where the lower jaw meets the skull base. In the interface between these two bones lies a cartilaginous disc. This disc helps reduce the friction between the bones and makes the movement smooth and easy. In a normal state, the cartilaginous disc is held in its correct position by ligaments. If for any reason the cartilaginous disc moves from its place and "gets stuck" in a forward position, it may interfere with the gliding of the lower jaw bone along the base of the skull, which causes a restriction in mouth opening, a phenomenon called TMJ closed lock (locking of the jaw).
Locking of the jaw joint may appear abruptly, or may be preceded by clicking in the jaw joints and/or temporary locking episodes (for seconds or minutes). Closed lock is not particularly painful, and only half the patients will complain of pain in the locked jaw joint.
Diagnosis of TMJ closed lock is based on patient history (a thorough conversation with the patient), clinical examination, and review of imaging such as CT or MRI.
The treatment of closed lock begins with non-surgical means such as occlusal splint (mouth guard), anti-inflammatory drugs, and avoiding hard and chewy foods. Roughly one quarter to one third of patients will respond to these therapeutic modalities. The rest of the patients will need a minimally invasive surgical intervention - arthroscopy of the jaw joint (TMJ), to achieve a normal mouth opening.
