I had covid few months back ..I feel my lower thigh muscles weak (just above the knee) so when I walk slow my knee bends back (hyper extend) and legs become tired when I stand for longer time .. sometimes feets heavy ..I don't know where exactly is the problems I also feel muscles and bones are not much connected or support each although I don't have pain in any part of legs my b12 ,vit d calcium was normal ..I don't understand what's the issue is this any deficiency or I still need to take more protein diet ..please suggest experts ..