Definition and General Information - Trismus is a painful restriction in opening the mouth due to muscle spasm. - It can refer to limited mouth opening of any cause. - 'Lockjaw' is sometimes used as a synonym for trismus and tetanus. - Normal mouth opening ranges from 35 to 45mm. - Males usually have slightly greater mouth opening than females.

Intra-articular Causes of Trismus - Internal derangement of TMJ / meniscus displacement. - Fractured mandibular condyle or intracapsular fracture. - TMJ dislocation. - Traumatic synovitis. - Septic arthritis.

Extra-articular Causes of Trismus - Trauma not involving the mandibular condyle. - Post-surgical edema. - Recent prolonged dental treatment. - Following administration of inferior alveolar nerve block. - Acute infections of the oral tissues.

Joint Problems Causing Trismus - Ankylosis can result from trauma, infections, and prolonged immobilization. - Treatment for bony ankylosis includes surgical procedures like gap arthroplasty. - Fibrous ankylosis usually results from trauma and infection. - Treatment for fibrous ankylosis involves trismus appliances and physical therapy. - Arthritis synovitis and meniscus pathology are also joint problems that can cause trismus.

Miscellaneous Causes of Trismus - Infections, such as odontogenic, peritonsillar abscess, and tetanus. - Dental treatment, including dental trismus caused by injury to the masticatory muscles. - Trauma, such as fractures and accidental incorporation of foreign bodies. - TMJ disorders, including myofascial pain dysfunction syndrome. - Tumors and fibrosis, which can cause limited mouth opening. - Drug therapy, where certain medications can cause trismus as a side effect. - Complications of radiotherapy and chemotherapy, which can lead to decreased mouth opening. - Congenital and developmental causes, such as hypertrophy of the coronoid process. - Hysteric patients, where emotional conflicts can manifest as physical symptoms like trismus. - Scleroderma, a condition marked by edema and induration of the facial skin, can cause trismus.