Temporomandibular joint disorders (also known as TMJ disorder or TMD) are a group of disorders that cause dysfunction and pain in the temporomandibular joints and jaw muscles that control jaw movement. If your temporomandibular joint is inflamed, injured or in pain, it can be difficult to open your mouth or chew your food, often because your jaw is locked. These types of jaw problems arising from TMJ disorder and bruxism, make essential activities like eating well, difficult.