Sciatic nerve pain can be divided into two cases: discogenic sciatica and sciatica due to muscle irritation/tightness. The first case refers to the pain caused by a disc that presses the sciatic nerve and the second case is where the nerve is affected by other causes largely due to muscle tightness. The sciatic nerve is one of the longest nerves stemming from the lumbar spine that goes all the way down to the foot. So if any of the muscles on its course gets too tense or inflamed, it can make the whole nerve sensitive and hence causing sciatic nerve pain.

According to the reference below, MRI scans of 3,000 ordinary people without back pain showed that 70% of them were abnormal, and many of them have protruding disks that pressed the nerves. The paper concludes that there is no correlation between disc protrusion and pain. Therefore, it seems more plausible that muscle tightness/irritation affect the nerves that pass around the muscles. Of course, this class will provide directions to resolve both cases.

References

Brinjikji W, Luetmer PH, Comstock B, Bresnahan BW, Chen LE, Deyo RA, Halabi S, Turner JA, Avins AL, James K, Wald JT, Kallmes DF, Jarvik JG. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. American Journal of Neuroradiology. 2015 Apr;36(4):811-6. doi: 10.3174/ajnr.A4173.