To find out what is happening, the therapist has to check for the endfeel of the movement.
To distinguish between intra-articular and extra-articular blockage, check the quality and feel of the blockage within the joint. If the blockage has a rubbery feel and gives slightly under pressure, it is likely to be an extra-articular (soft tissue) blockage. If the blockage seems inflexible and range of motion ends abruptly, there is probably an intra-articular (bony) blockage.
The Short Formula
NO YES = Agonist
NO NO = Antagonist or Joint