Skel format is able to read initial position and velocity of each joint.

For example:
<joint type="revolute" name="my_joint">
  <init_pos>1.57</init_pos>
  <init_vel>0.0</init_vel>
</joint>

<joint type="universal" name="my_joint">
  <init_pos>1.57 -1.57</init_pos>
  <init_vel>0.0 0.0</init_vel>
</joint>