The Monteggia injury is defined as radial head dislocation with a fracture of the ulnar shaft. This combination should be sought routinely in patients with ulnar fractures, even when the displacement is small. The emergent management is simple, as reducing the ulnar fracture is usually sufficient to stabilise the radial head. Internal fixation of the ulna deserves to be widely used to fully stabilise the radial head. Irreducibility of the radial head at the acute stage may indicate an interposition, which requires open surgery on the joint. Radial head dislocation may occur even with minimal displacement of the ulnar fragment. Chronic Monteggia fractures are more challenging to treat and their outcomes are more variable. The radial head becomes irreducible after 2 to 3 weeks. When a simple surgical approach fails to ensure stable reduction, the most widely used method at present is open reduction of the radial head and proximal osteotomy of the ulnar shaft. Stability must be obtained intra-operatively. Without treatment, radial head dislocation may be well tolerated for several months or even years. In the long term, however, osteoarticular remodelling results in loss of joint congruence, pain and, eventually, osteoarthritis. Radiographs must therefore be obtained on an emergency basis and analysed with great care to avoid missing a Monteggia fracture.