Sorry to hear of the sudden pain. I had surgery 15 months ago, and I’m still easing into running.
I’d highly recommend that you go to physical therapy … If I had to guess, I would say your glutes are weak and inactive, not propelling you forward anymore. Thus the muscles that are activating (most likely in the front) are overwhelmed and thus the pain. That was my problem at 6 months when I went to PT. My therapist had me stand this way and that … and lie this way and that … and she pushed against my leg … asked me to resist … and she quickly concluded I had a weak and inactive glute medius muscle that is key for propelling us forward.
It’s quite easy to develop a major muscle problem (and a glute problem) … because in the years before the surgery, we make compromises in how we walk and move … and also because just aging in our society tends to involve a lot of sitting and muscles can go to sleep.
A really good PT should be able to pinpoint the problem and develop exercises to activate and strengthen the right muscles. (Sometimes we can have strength, but through office living and sitting, the muscles stop firing. You probably need exercises to strengthen and activate muscles.)
Tip: find a PT that is really good … and that people report is fun to be around. Go online and find some place that is fun to go to. I’ve gone to PT multiple times and it was only at 6 months after hip replacement (when I was having serious problems running and moving) that I made sure to read reviews and I found a PT place that was so much fun … the clients chatted and cracked jokes … and there was great conversation. And none of this detracted from the exercising under close supervision of the PT.
And because I loved the Pt … and loved the atmosphere … going to PT wasn’t work. It was fun. I never missed an appointment in 5 months. (You probably won’t take that long, but I also had back issues.)
Sometimes surgeons can miss problems on the X-ray, but what they are looking for is generally that the bone (white on the x-ray) has grown into the device. They can see gaps if there is a problem with the device not binding to the bone. But sometimes surgeons can miss problems on the X-ray. I was having a muscle problem a few months back, and I went to my surgeon to make sure the device was OK … and he showed me how the white streaks on the x-ray (bone) was right up close (with no gaps) to the device. (Turned out some stretching fixed my issue.)
The good news: Since you can apparently walk and do the elliptical without pain … I’m thinking this is most likely a muscle problem. Severe problems (device problems like a loose device) tend to make even walking painful.
You can ask your surgeon for a PT script … a GP can also write out a script. Going to PT to resume running is actually legit.