Here I suggest with patients who are diabetics along with hyper tension problem its common that they develop often swelling on feet and ankle area. Now when we see there is a discoloration of skin along with swelling that means there is a problem with circulation too. As well if this area start paining along with change in skin color then its time to do some tests like dopler study and sensory evaluation for your lower limb blood vessels and nerves. And based on that only the treatment can be plan. I suggest to go ahead and Dont be scare of doing any test or with test report. Because if there is some thing happening wrong you need to know what it is and take treatment in early stage so you can cure it fast and come out of it early. Since you are diabetic with different joint arthritis as per your explanation, I also think so that there is a problem with nerves and blood vessels supplying to lower limb. How ever the conformation can be done only with physical evaluation and test report. I can only suggest to do some stretching exercise for legs to improve circulation and take the treatment properly. Think positive live healthy take appropriate rest and balance diet as per your medical health. And once you start recovering do regular exercises like stretches, walking or cycling etc. Take care.