Dear OpenSim user, OpenSim version 2.2 is now available for download. OpenSim is freely available to the biomechanics research community and enables modeling and simulation of human and animal movement, including inverse dynamics analysis and forward dynamic simulation. The new version contains enhancements to the user interface, the ability to set bounds on activations when solving static optimization, and the ability to run forward dynamic simulations using controls provided as a storage file. It also contains a new robust moment arm solver and upgrades the dynamics engine to Simbody version 2.1. Updated examples, Doxygen documentation, Developer's Guide and User Guide are also included. The new version works out of the box on Windows 7 machines, and API distributions on linux & Mac are also available. The software, models, tutorials, and example simulations are available at the project website: https://simtk.org/home/opensim. We will start a Webinar series to demonstrate the functionality available in OpenSim early next year. Best regards, -Ayman Habib On behalf of Scott Delp and the OpenSim team.