No experience what-so-ever, but it sounds like you need to discuss flexible working (either flexible hours, working from home, or both) so that you can continue to develop your career with the option to work as and when pain not be a concern.

Maybe your employer will support you in this. Maybe you need to find a new employer who will. Maybe you need to set up shop on your own so can decide when to work to suit your health.

Of course all irrelevant if the pain is constant rather than on / off.

I don't have any feedback on the physical aspect. But I would recommend making sure you pay attention to your mental health as well and consider talking to a professional there. Finding the right one can be a challenge but a good professional will help you learn how to function better through the pain and learn how to anticipate and mitigate any anxiety and depression that may accompany it.

I don't know if you are US based or not - my advice is based on experience in the US

I am also not familiar with your condition and it's treatment but I have worked with a few people with debilitating medical conditions

1) If a treatment exists but requires a long convalescence period that would keep you from working - take the treatment. Projects will move along fine without you and you'll hopefully comeback healthier and more productive. Coworker put off a treatment until he 'had' to do it and 'had' to take the time off work and kicked himself for not doing it sooner. He missed out on more time with an improved quality of life

2) Make sure your treatments are not being limited by your insurance plan. A different co-worker had a condition that was cheaper to treat with drugs (indefinitely) than to have a one time (expensive) procedure performed. The drugs left him near comatose at his desk at some points and in pain at other points. He got married and was able to switch to his wife's insurance plan and got the ore expensive treatment

Damn! Sorry to hear about the health problems. No pity party necessary, you are probably going through a lot day-in-day-out. That is an accomplishment that needs to be recognized.

Anecdotal advice:
I have a similar chronic condition too. They diagnosed me about three years into my career during the glory years of being a carefree 20-something. There was a lot of career and social opportunity at the time. The chronic physical pain absolutely devastated me for about three years. I was scared, physically wrecked, and mentally destroyed.

I lost jobs, dealt with a lot of business-first people, and absolutely lost all ambition to compete at work. My dad's advice: "Find a good job that has benefits and then try to outlast the 3-month probation period so you are in the system." Smart strategy, but archaic and detrimental in the long run. I listened, as a dumb 20-something would, and it helped financially for a couple years while we figured out medications (including an immunosuppressant). After some major improvements, I ditched his advice, quit the job, moved away, took loads of time off, and discovered some important personal lessons.

Here are things that I would tell my younger self to focus on. Hopefully they can provide you with some strategies:

1) You are still valid as an engineer. Remember that. More importantly, you are still valid as a person.

2) Talk about your condition with people. I don't think it's necessary to expose all that stuff at work, but it certainly helps with adjusting other's expectations and your boundaries.

3) Take recovery time when you need it.

4) Enjoy your outside life. Like...really enjoy that part of life. You see more improvements when that is your focus. You'll be less depressed. Your concentration or capacity to solve problems will improve without that mental weight.

5) Take the treatments that will make your life better. Medication? Sure. Doctor's orders for rest? Absolutely. A counselling session? Heck yeah! If it works, do it again. If it doesn't, try something else. Be patient.

6) Separate the wheat from the chaff: people that don't understand your boundaries don't really need to be in your life.

7) Keep learning. I really wish I didn't give up as hard as I did during those painful years.

Structural engineers are notorious for being complete competitive ego-maniacs, which makes it hard when the pain makes you feel inadequate and weak. But there is a lot of reclusive brilliance out there that needs that quiet space to find their voice and place in our societal structure. Reach out if you need too.

Thank you all for your feedback. Skeletron thank you for sharing your story and perspective. Mr Hershey I think it is a great suggestion to speak to a mental health professional. I used to see a therapies regularly years ago, it's probably overdue!

Truckandbus I do live in the US. So far my insurance has been covering the medication I am taking, and supposedly this medication is the among the best non-surgical treatments for the condition, so there's that.

RandomTaskkk some degree of flexible schedule may be in order in the near future. One thing I struggle with schedule-wise is making doctor's and physical therapy appointments, since most such offices are only available 8am to 5 pm. So far I haven't gotten any push back when i've had to take a half day here or there, but sometimes I feel guilty about it which I know is silly.

For my wife, a supportive boss and flexibility to work from home made all the difference. Hard to find though, especially at a company where you haven't built up a track record beforehand.

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just call me Lo.

As skeletron said, this is really an accomplishment that needs to be recognized.
"When The Going Gets Tough The Tough Gets Going"

As someone who has seen my mom deal with chronic back/pelvis pain and over 20 back surgeries, I have witnessed what it can do to someone (though never pretending to fully understanding it myself).

I can't speak to the career side, but I definitely second the mental health side. Seek a professional, and also look into a group called Chronic Pain Anonymous. They have physical meetings, video conference meetings, etc. They can accommodate physical limitations. You can find people likely in similar situations. A better mental state can have an effect of "lessening" physical pain, from what I understand.

Yes, you're still an engineer. Unfortunately, being a male-dominated field, we're more likely to be influenced by our peers and be discouraged from talking about our "feelings". But I say to hell with that and do what's best for you.

Best of luck

Sadly to my knowledge, there's not much to be done for arthritic conditions other than bone fusion, which is still no guarantee...
As someone who also suffers chronic spinal problems, I have to agree with the others:
Mental health = very important. It's so easy to become depressive and feel worthless, which reduces you capacity to manage and also pushes away the people in your support network.
Flexible work hours. This! Some nights you just don't sleep, and this throws off your concentration the next day. If you can organise a scheme with your boss, or get into self-employment, this allows you to use those wasted hours staring at the ceiling to do something productive, and take your mind off your body.
Finally, appropriate physical therapy can help a lot. If you can make the time and afford it, a chiropractor is often extremely helpful, despite what many doctors seem to think, and hydrotherapy or even just gentle swimming/walking in a heated pool can do wonders for taking the strain off your back and relaxing the muscles. As I'm sure you've already found, too much inactivity is just as bad as too much activity. Find the positions that work for you, move often, even build a support frame if needed to help take some of the weight of your upper body while at a desk. It sounds stupid, but it can help. One of the truck drivers I worked with had made up a simple frame which hooked over the top of the seat and strapped around my ribcage to provide some support. It made getting in and out cumbersome, but allowed him to work a full day with minimal suffering, as opposed to the maybe 5 hours he could work prior.