This paper reports the study of the osseous remains of an adult male (30–35 years) from a Spanish urban necropolis dating from the pre-industrial age (17th–18th centuries). We have diagnosed the presence of a severe unreduced forearm fracture, which has been classified as a Type I Monteggia fracture in the left arm. Injury occurred by a complete and poorly resolved ulnar fracture in its upper third. As result of this ulna fracture a radial head dislocation also occurred, creating a new articular surface on the humerus. The ulna also underwent two different types of angulation. The purpose of this study is to evaluate the anatomical changes of the elbow joint bones after a Monteggia fracture, assessing the completeness of functionality on the arm of this man. After the fracture, this individual lived the rest of his life with a permanent dislocation of his radius; therefore, loss of the forearm rotation, cubitus valgus, elbow instability and pain were all present. Movement was limited to an intermediate position or semipronative. A detailed description of the pathology is also accompanied by a discussion of the historical-cultural context in which this man lived and the common diseases of the population to which he belonged.