With your client sitting, press into the SI joint with your knuckles or middle phalanges. Have your client slowly bend forward and toward the contralateral side so that their hand slides down the outside of their calf on the contralateral side. Slowly slide down the SI joint with pressure as your client bends forward.
This can be more effective with eccentric contraction. Do the technique as before, but with your hand on the client’s ipsilateral shoulder. Press their shoulder down and toward the contralateral knee while your client resists. Begin with gentle pressure and instruct your client to resist but to let you win. If this is pain-free your client can gradually increase the resistance they provide.