Welcome in H.C.M.
I have gone through your query regarding weight loss
and bruises above knee. Though you have fever as well along with throat infection
Here I would like to tell you that some times in viral fever
and various other fevers platelets count in blood goes down and in that case purpuric spots appears on skin ,and they look like bruises.
You are now advice for-
1- Blood- CBC, ESR
, blood sugar (F & PP )
2- Blood urea, serum creatinin.
I hope these investigation will be helpful in deciding the real facts.