Well I officially heard back from all Sam's docs with the test results from Tuesday:
Pulmonology.... chest x-ray shows lung abnormality (which we already knew about). basically his lungs are a weird shape most likely from prematurity... nothing new there... but otherwise look great!
Cardiology... they did an echo under sedation to follow up with Sam's history of pulmonary hypertension. In a word... FABULOUS. No problems to report and everything is well within normal.
Orthotist... the bone scan (amazingly) was completely normal.
So I guess that puts us back at square one. We have no idea why he is limping and gimping around. Maybe he pulled something (which would not show up on any of the tests) or maybe it is just growing pains. Who knows. So... we will continue to watch him for any changes over the next several weeks and follow up with the orthotist the end of August.