Existing research on prolotherapy began in the 1930s when Lerich first described the rich supply of nerve endings in articular ligaments. This was re-introduced by Gardner in 1953. Also in the 1950s, Hackett, who described most joint pain as ligamentous, was the first to scientifically demonstrate a method of strengthening ligaments by injection of a proliferant solution. At that time, the use of an irritant solution was thought to work by creation of a scar tissue rather than by development of a proliferative response. As pain was perceived to arise when normal tension on a ligament stretched the relaxed ligament fibers, which resulted in abnormal tension and stimulation of the sensory nerves because the nerve fibers did not stretch, reduction of pain was thereby thought to arise with stabilization of these relaxed ligaments through generation of a strong scar tissue about that structure. Reduction of pain was realized by Hackett who reported an 82% success rate in the treatment of chronic spinal pain in 1816 patients treated during a 20-year period.