I also experience joint pain from Solanine containing plants, which I was surprised to find out includes other plants including fruit like blueberries. Blueberries cause swelling and pain in my fingers. I found out that I have a gene variant for the gene MTHFR which is involved in processing vitamin B9. Sensitivity to solanine is one aspect of having the homozygous form of MTHFR C677T. This variant is also associated with other symptoms including depression, anxiety and high homocysteine levels which can increase the risk of heart problems. It can be tested for with a simple blood test. I tested this effect by eating a bowl of cherry tomatoes I grew organically at home, and they left me feeling stiff and with joint pain for three days. I avoid the solanine family and blueberries now.