Furthermore, a bad knee can cut the speed. If he pushes from it, the knee is part of the pitcher's power. Look at video of Tom Seaver: entire motion is low, and he drives with his right leg. If it's his off-side knee, it will hurt every time he lands and twists into a fielding position. The extra step that made Harvey Haddix famous as a great-fielding pitcher..."The Kitten". (Harvey Who? The Cards/Pirates who pitched the 12-inning perfect game only to lose PG, shutout, and game in the 13th.)