Hi Maggie!
For an uncompensated Trendelenburg gait pattern, during stance on the affected limb, the pelvic drops on the contralateral (swing) side and there is usually minimal or no trunk lean. The hip abductors are weak (glute med) and cannot generate enough force to keep the pelvis level. So, this is a sign of pure hip weakness and the child hasn’t learned how to compensate yet. This usually happens early in a neuromuscular case or just after hip surgery.
With compensated Trendelenburg gait patterns, there is an ipsilateral lean of the trunk toward the stance limb and the pelvis may drop a little bit, but less than expected. The trunk is shifting to keep the center of mass closer to the hip joint and to keep the pelvis more level. This is showing that the child has weak abductors but is showing some motor planning to counteract the weakness using the trunk. This is seen a lot in our kids with CP and myelo.
Uncompensated = no trunk lean, pelvis drops
Compensated = trunk lean, minimal pelvic drop
I hope this helps!
Jessica