I have a very similar rash on my outer right elbow. I have been putting hydrocortisone on it and it appears to be improving.
Hello,
It can be frictional lichenoid dermatitis or dermatitis herpetiformis. Typical symptoms include burning, stinging, and intense itching and rash consists of small vesicles on the extensor aspects like the knee. It is an autoimmune blistering disorder associated with a gluten-sensitive enteropathy. Investigation which needs to be done is biopsy skin which is the only investigation to diagnose this condition.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.