@Spongebob Sorry to hear about your hip pain. IP (iliopsoas, these 2 muscles are so close to each other, they are usually lumped together) tendonitis is one of those situations that seems pretty straightforward and most times, it is. The ortho/PT people are always going to start simply and work their way forward. It's logical, easier to keep track of your progress, and not surprisingly, these simple things usually take care of the problem. It's kind of a Sherlock Holmes mystery solving exercise. I'll try and address what I understand about the subject.
1. Something is aggravating the tendon. So, what is it and what can we do about it?
You alluded to a couple of possibilities:
a. A particular exercise(s) can cause the IP to get irritated. You stop said activity and similar ones, rest, ice, and take NSAIDS as appropriate, if you are able.
b. The muscle/tendon can become shortened/tight with sitting for long periods of time with work or an activity. It can also do this while we wait for our THR. Gentle stretching regularly can help the muscle return to its proper length and role (and free up those other counter muscles.) A well-trained PT can manually pressure release this muscle/tendon to get it to relax, as well.
c. Sometimes a tight tendon can be sliding over the edge of the acetabular cup component. The diagnosis and treatment plan here will be from your OS.
Most of the above can be self-directed or in conjunction with your doctor/care practitioner. He or she may even offer a more potent anti-inflammatory to aid your endeavors. Then, it is a wait and see if anything helps. The ball always lands in your court to let your care team know if the pain continues or gets worse.
2. Let's talk about pain. How is your pain? How long have you had it (recently or pretty much ongoing?) How do you rate it? Is it intermittent, all day, or interfering with your daily activities? Do any of the treatments above help? Pain level and the effect on your life also drives diagnosis and next steps treatment.
a. If the pain is stubborn and you can't get it to settle, the next step could be an injection into the tendon. This is an anesthetic with a steroid. The results can be mixed but the hope is that the steroid will get that tendonitis to finally calm down.
b. What if nothing seems to help? If you've given it your best shot, then surgical intervention may be necessary. This is especially true if a physical impingement (like the acetabular component) is the cause of the tendonitis. This consists of lengthening the tendon by cutting some of the fibers, usually through an arthroscopic procedure.
I hope this sheds some light on this. The kicker here is that each step takes time and patience to sort out and move through. Trust me. I have been through them all. Let me know if I can be of further assistance. Blessings as you look for answers.