An ankle replacement procedure consists of replacing the worn-out joint surfaces of the ankle with metal and plastic components that are shaped to allow continued movement of the ankle. There are several different types of ankle replacement available. Infinity ankle implants are already routinely used in NHS hospitals. The INFINITY™ with ADAPTIS™ and EVERLAST™ ankle replacement system is a development of the Infinity ankle implant, designed to attach to the bone better and to wear out more slowly. The purpose of the UK ADAPTIS™ Study is to assess the performance and function of the newly introduced INFINITY™ with ADAPTIS™ and EVERLAST™ technology Total Ankle System for total ankle replacement (TAR) or arthroplasty (TAA) and EVERLAST™ Poly Insert that modernises and streamlines Stryker's TAA/TAR portfolio. UK ADAPTIS is a prospective multi-centre cohort series of INFINITY™ with ADAPTIS™ and EVERLAST™ Technology with Poly Insert for patients requiring primary total ankle replacement (TAR) i.e. Total Ankle Arthroplasty (TAA). Patients meeting the criteria for the study will be asked to enrol by providing written informed consent. The patients will be monitored clinically by post-operative follow-up examinations and Patient reported outcome measures (PROMs) (Manchester Oxford Foot \& Ankle Questionnaire (MOXFQ), Ankle Osteoarthritis Scale (AOS), EQ5D-5L). Intended use: It is intended to give a patient limited mobility by reducing pain, restoring alignment, and replacing flexion and extension movement in the ankle joint. Indications for use: * Patients with ankle joints damaged by severe rheumatoid, post-traumatic, or degenerative arthritis. * Patients with a failed previous ankle surgery.