Box rest and hock arthritis/SI issues

[JoyousMintDeer]

My horse has been on long term box rest after a tendon sheath injury. Previously he’s been diagnosed with very mild arthritis in his hocks but responded really well with injections. He’s has SI soreness but this has been resolved with using a physio. He’s back starting ridden work and turnout following the injury but now displays pain reactions to upwards transitions both ridden and on the ground. He’s had his hocks re done over a month ago so that doesn’t seem like an issue which but it looks like his SI is the problem now.
Looking to mediate the SI but wondering if anyone has had similar issues and if there horse has come back into full ridden work? He previously evented but don’t want to get my hopes up that he ever will come back to do that again or if he should look to have a quieter life

Steriod injection into the SI worked very well for my horse although he'd had an accident not a gradual wear and tear problem. He had it repeated about 3/4 years later also, he came back into work, but slowly, each time, just low level dressage as a suspensory ligament issue meant I had already stopped jumping him. I did a lot of in hand work after the injection to get the joint mobilised and strengthened so if you plan to go ahead with this get your physio on board and have a rehab plan ready. It's not a quick fix.