Knitting is so bad sometimes I don't know how I can ever keep on doing it. It bothers me a lot in my arms, so I'll normally just take a break and it generally gets relieved. If not, massaging is helpful. I've never tried any creams or lotions, I'm a little wary because I have super sensitive skin. I have more trouble with my back and neck, though, and sensitive areas where I've broken bones in the past.
Posture seems to be real important, slouching shoulders has regrettable consequences later. And it puts less strain on the back if you avoid bending over, and use squat at your knees instead. Another helpful tips is to keep your back straight and to use a lumbar support. Even a rolled up towel behind your lower back is helpful.