The forearm is an autonomous functional musculoskeletal unit based on three osseoligamentous stabilisers. However, until recently, no validated forearm specific assessment score was available. Two elbow surgeons and one hand surgeon developed the Forearm Italian Performance Score (FIPS) that proved to possess an adequate face validity. The aim of the study is to report on the convergent validity and reliability of the FIPS. One hundred patients operated for longitudinal malalignment of the forearm were recruited in a prospective cohort study. Four elbow-wrist scales were administered twice, one week and three months after surgery. Construct Validity, inter-intraobserver Reability and Internal Consistency were tested and found to be adequate. The FIPS was found to be simple and suitable for use in a clinical setting. The FIPS is the first validated tool available the osseoligamentous forearm lesions scoring.