Osteoarthritis (OA) is one of the most frequent temporomandibular joint (TMJ) disorders due to proliferative changes in the synovia as well as primary degeneration of the cartilage and surrounding tissues and destruction of bone structures. The main aetiological factors are trauma, infection, and systemic inflammatory diseases as rheumatoid or psoriatic arthritis. Several specific inflammatory and pain mediators (PGE2, 5-HT), and cytokines (TNFα, IL-1β) are important in the pathogenesis of OA. Diagnosis is based on clinical symptoms, signs and parameters, as well as on radiological investigations (CT, MRI). The main focus is placed on treatment with nonsteroidal anti-inflammatory drugs, interocclusal appliances and on surgical treatment as arthrocentesis, arthroscopy and open reduction. Long-term results of TMJ arthroscopy demonstrated high accuracy for adhesions, fibrillations and degenerative changes of bone structures. Arthrocentesis and arthroscopic surgery, lysis and lavage, for treatment of TMJ disorders of fer favourable long-term results with regard to increasing maximal interincisial opening, reducing pain and dysfunction.