Do horses get 'immune' to joint supplements?

[Chestnut mare]

My mare has been on superflex for the last 4 years. Recently she's been a little stiff behind and the back lady has confirmed arthritis.
She's 17 which isn't old for a pony but she needs a little help.
I think I should change from superflex to another joint supplement as shes no longer getting the benefit from her current 1.
What do you all find effective for your horses? There are so many to choose from .

 

[potty_4_piebalds]

I don't know if they get immune or if the arthritis just gets worse, I had a pony that was diagnosed with arthritis in his hocks at just 8 years old, I used loads of different supplements and found stride was the best for him but then after a while stopped working and it is quite expensive. I have heard a lot of good things said about premier flex but never used it myself.

 

[TheMule]

No, the biological effects (if there are any worth talking about) shouldnt wear off.
Superflex is quite comprehensive, one of the better products around- perhaps a joint supplement just isn't sufficient to manage the amount of wear and tear, remember it has no pain killing properties

 

[Chestnut mare]

Yes, maybe worth adding devils claw for a bit of pain relief ?