I saw my new orthopedist for the first time today (my previous one was retired). I received surprising news: I have sciatica from my back (not the hip, such as the piriformis muscle). An MRI of my back shows disc bulging and spinal stenosis right where the sciatic nerve exits on the left side. The condition is moderate, so the nerve is not compressed under normal conditions. But anything that inflames the disc can compress the disc and cause sciatica. This explains why I started experiencing sciatica symptoms about a month ago after exercising too strenuously. Then after a few weeks it calmed down and I increased it again with more exercise. It also explains why the PT exercises I was doing, which train both the piriformis muscle and the sacroiliac joint, didn’t work as well as in the past because they don’t directly target the lumbar spine. For now he will give me a course of prednisone, which he thinks will be enough as the sciatica symptoms have already largely calmed down. I am allowed to exercise, including cycling and weight training, as long as there are no signs of sciatica. I will start increasing the intensity and decreasing it as needed. I will also look at PT exercises specifically for the lumbar area (you can find a good reference here). I want to build up the muscles in this area so that they are less vulnerable in the future.