The term "unstable lesions of the forearm" (ULF) was born to more easily describe how a partial or complete instability of the forearm unit might occur due to a traumatic loss of the transverse or longitudinal connection between the radius and ulna. For such an alteration to occur, at least two of the three main osteoligamentous locks (proximal, middle and distal) must be interrupted, often in association with a radial and/or ulnar fracture. Examining the historical patterns (Monteggia, Galeazzi, Essex-Lopresti and criss-cross lesions) and variants described in the literature, out of a total of 586 recorded interventions for forearm trauma, two elbow teams and one wrist team selected 75 cases of ULF. The aim was to describe the instability depending on its clinical and radiographic features, together with the anatomopathological evolution of the lesions based on the time of diagnosis and treatment. The clinical results, evaluated using a new score (FIPS) the Forearm Italian Performance, revealed a correlation between earlier diagnosis and treatment and a better score. The authors suggest a synoptic table that describes 1) the type of instability (proximal transverse, distal transverse, longitudinal and transverse, proximal and distal transverse), 2) classic patterns and variants with characteristic lesions and evolution over time (acute, chronic dynamic, chronic static) and 3) the three forearm constraints and segmental involvement of radius and/or ulna using an alphanumeric classification. Finally, some generic surgical suggestions are proposed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)