Shop X-Line X-Line Products Designed by in-house podiatrists, our X-Line range offers precision treatment for a range of foot and lower limb conditions. See our full range of products below. HomeShopX-Line X-Line TPD Insoles The TPD insole is an orthotic device designed for Tibialis Posterior Dysfunction, a condition that can cause rapidly developing flat feet and pain on the inside of ankle, arch and/or shin. £28.95 + More Stay one steap ahead in the treatment of foot and lower limb conditions. Call the HealthyStep team on 01457 839549