Hi,

I agree with all of the above but the popping sound and the mechanism of injury can also indicate a tear of the labrum - the cartilage that helps to deepen the glenoid fossa.

Your XRays look like your shoulder is slipping downwards (as mentioned above). This could be because of ligament and/or muscle damage OR the cartilage was damaged and allowing the shoulder to "pop" out that way.

Otherwise good luck and let us know what is going on. BTW, Wikipedia reference-linkMRI with arthrogram would be a nice investigation to have - even a CT arthrogram.

Cheers