When you hear about erythema nodosum, you will most probably associate it with something visually unpleasant as this disease progresses both internally and externally. It is possible to notice red lumps and rash in several damaged areas. As a rule, those are the lower extremities, especially knees. The lumps quickly become rather sensitive and cause itchy and painful feeling. The worst thing is that nodules can become rather large in short period, which makes this sort of skin’s rash even more troublesome.