Follow-on from previous shingles questions any advice?

My previous question regarding my elderly father who contracted shingles 7 weeks ago - he has seen a doctor twice - once within 72 hours of contracting it and then abut 4 weeks into it - both offered painkillers nothing else. Now he is approaching his 7th week (tomorrow) he is still very weak and although most of the spots have dried up he is still suffering badly with his knee and the surrounding area - with red blotches and white blisters appearing and burning - surely - i would have thought - by now he would be healing - any adice on this matter would be much appreciated.