I'd also suggest looking at your liver, as liver congestion can manifest as knee joint pain.
As can manganese deficiency (or its opposing mineral present in over abundance).
If it helps, during supplementation with Iodine my joint pain has decreased significantly. Hopefully it will just be a temporary detox reaction to the iodine.
Ensure you're following the correct salt and vitamin C protocol, Im inclined to keep at the same dose and if symptoms increase to drop back but thats just the cautious part of me!