The human hand is a marvelously useful biomechanical device that has inspired numerous depictions and models, however its complexity, makes the construction of accurate visual and physical models an extremely challenging goal. We present, Helping Hand, a realistic skeletal musculo-tendon model of the human hand and forearm. The model permits direct forward dynamics simulation, which accurately predicts hand joint orientation given a set of muscle activations. We also present a solution to the inverse problem of determining an optimal set of muscle activations to achieve a given pose or motion; muscle fatigue, injury can also be specified, yielding different control solutions that favor healthy muscle. The model can take kinematic pose data and predict animation sequences of the hand to fit or indeed physically improve upon kinematic data. Lastly, we demonstrate ways to isolate and visualize muscle groups as their effect on hand motion is animated.