This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
In an open-newel stairway the rails usually meet the newels one above the other. To bring them to the same level, the rail must be ramped, and sometimes they are ramped and kneed - the latter being a concave easement with its upper end forming an angular knee.
When the knee is convex, the combined curve is then called a swan neck or sometimes a goose neck. The lower ends of rails abutting against the newels may be either straight or curved. When curved, the rail is said to be eased, and the curved portion of the rail is called the easement, and this arrangement requires the newel to be somewhat longer.