I used one for tennis elbow and it certainly did ease the pain until it was healed. I have no knowledge how it would be for Arthritis, but it’s worth a try. My machine was quite small and fitted with a Velcro strip.
I'd recomment an Acti Patch .these are like disposable tens .You wear them 24/7 if needed .My daughter used them for fibromyalgia pain and found them better than a conventional tensm/c because she only needed to put it on once and could leave it in situ for days .You can get them from some branches of Boots or from Amazon My sister is currently using one for post operative pain with great results
My friend has bad arthritis and now also has heart issues. She was advised to stop using her tens machine as it could cause more issues with her heart? She used to use it daily. Worth asking a chemist for advice perhaps.
I got one for my husband at his request for joint and muscle pain. Eventually he pronounced it "useless" and I used it for varying problems. I can't say that it helped me either so I then passed it on to someone else with a new set of pads.