Since I cut out the poor quality greens and veg and increased my consumption of top quality fresh fruit, my joints, especially my knees, are much better in a bit under 4 months.
I am quite sure the 32+ VVF pluots I have been eating lots of have much to do with this. When cooked lightly, they jell up very well on their own and need no sweetener at all.
I suspect that fruit pectin, like so many other things, is only as good for us as its source. While eating average foods and adding the store-bought pectin may help some, nothing beats finding and eating top quality foods for at least 10-20% of one's daily consumption and eliminating poor ones entirely.