TENS machine recommendations

[EauRouge]

Hello,

I've been suffering for a while with a sports/gardening injury that keeps flaring up not helped by my inability to relax and I was thinking of getting a TENS to help with it. There are millions available and I'm not sure what features I need or anything. Would anyone be able to recommend one please? It's for my lower back and hips if that makes any difference. Thank you :)

I forgot to say, I used a TENS machine in labour with DD2 and found it really helpful so I have tried one before and got on with it. But it was 4 years ago and I can't remember much about it.