Arthritis of the TMJ
From bonepath
Arthritis is degenerative joint disease, osteoarthritis (OA) thus referring to bony degeneration. OA of the temporomandibular joint (TMJ) is believed to begin with the inflammation and/or destruction of the deep cartilage overlying the mandibular condyle (Hodges 1991). When the inflammation progresses, the bony degeneration associated with OA manifests as irregular surface, erosion, osteophytic growth, and or/eburnation (polishing) of the glenoid fossa and/or mandibular condyle. In an experimental study in rats, Kuroki and colleagues (2010) found that in their rats with TMJ OA, the condyles tended to be osteophytic, whereas glenoid fossae tend to display bony erosion. These arthritic rat condyles also had expanded marrow cavities compared to non-arthritic controls; unfortunately it is not clear how well this model recreates OA of the TMJ in humans. Clinically, OA of the TMJ presents with joint pain, effusion (swelling), and pannus of synovial tissue (Okochi et al. 2011). Severe cases of OA can result in major bony deformation, including complete loss of the condyle in a few years (i.e. Okochi et al. 2011). Pain due to arthritis can lead to mandibular dysfunction and dysmorphic facial features, such as micrognathia (Cannizzaro et al. 2011).
TMJ OA occurs has highest prevalence among older adults, occurring in anywhere from 20-40% of adults aged 40-60 years (Hodges 1991, and references therein). But OA of the TMJ is not restricted to elderly people. Juvenile idiopathic arthritis affects an estimated 1 in 1000 children, and the TMJ is involved in up to 93% of cases (von Bremen and Ruf 2011). Thus, the occurrence of OA of the TMJ varies across ages, though it probably most commonly affects older adults.
The age-specific frequencies of TMJ OA suggest a complex, multifactorial etiology. Hodges (1991) found a significant association between presence of OA at the glenoid fossa or mandibular condyle, and age and level of dental attrition in a large British skeletal sample. This suggests that degeneration and inflammation of the TMJ can occur as a result of age-related tooth wear, possibly related to increased lifespan in recent times. But a lifetime of TMJ wear-and-tear is not the only cause of OA, and the condition is not confined to older age groups. OA of the TMJ has been identified in cases of juvenile idiopathic arthritis (Twilt et al. 2004, Ravelli and Martini 2007, Cannizzaro et al. 2011, von Bremen and Ruf 2011), psoriatic arthritis (associated with the skin disease psoriasis; Rasmussen and Bakke 1982, Ravelli and Martini 2007, Farronato et al. 2010) and rheumatoid arthritis (Nordahl et al. 2001, Okochi et al. 2011).
References
Cannizzaro E, Schroeder S, Müller LM, Kellenberger CJ, Saurenmann RK. 2011. Temporomandibular joint involvement in children with juvenile idiopathic arthritis. Journal of Rheumatology 38:510-5.
Farronato G, Garagiola U, Carletti V, Cressoni P, Bellintani C. 2010. Psoriatic arthritis: temporomandibular joint involvement as the first articular phenomenon. Quintessence International 41:395-8.
Hodges DC. 1991. Temporomandibular joint osteoarthritis in a British skeletal population. American Journal of Physical Anthropology 85:367-77.
Kuroki Y, Honda K, Kijima N, Wada T, et al. 2011. In vivo morphometric analysis of inflammatory condylar changes in rat temporomandibular joint. Oral Diseases 17:499-507.
Nordahl S, Alstergren P, Eliasson S, Kopp S. 2001. Radiographic signs of bone destruction in the arthritic temporomandibular joint with special reference to markers of disease activity. A longitudinal study. Rheumatology 40:691-4.
Okochi K, Kretapirom K, Sumi Y, Kurabayashi T. 2011. Longitudinal MRI follow-up of rheumatoid arthritis in the temporomandibular joint: importance of synovial proliferation as an early-stage sign. Oral Radiology 27:83-6.
Rasmussen OC, Bakke M. 1982. Psoriatic arthritis of the temporomandibular joint. Oral Surgery, Oral Medicine, Oral Pathology 53:351-7.
Ravelli A, Martini A. 2007. Juvenile idiopathic arthritis. The Lancet 369:767-78.
Twilt M, Mobers SMLM, Arends LR, ten Cate R, van Suijlekom-Smit L. 2004. Temporomandibular involvement in juvenile idiopathic arthritis. The Journal of Rheumatology 31:1418.
von Bremen J, Ruf S. 2011. Orthodontic and dentofacial orthopedic management of juvenile idiopathic arthritis: a systematic review of the literature. Orthodontics and Craniofacial Research 14:107-15.
