First, as you probably know, you could not sue the store (your employer) for the injury if you took worker's comp: you are allowed to sue your employer or get worker's comp, but not both.Second, you almost certainly could not successfully sue the manufacturer for how they stacked their pallets, since those were stacked for shipping. Once it got to the store, it was out of the manufactuer's hands and the store could put them out, display, stack, etc. them however the store wanted; the manufacturer is not responsible or liable for the store's decision to put the pallet out as is.Third, even if you could sue, you can only sue for the degree to which the impact made your "bad knee" worse--not for anything due to the evidently pre-existing condition you had. And you would need to hire a doctor to testify, which can potentially cost thousands of dollars if you go to court. For a red and swollen knee which already had issues, you could spend more on the lawsuit than you'd get back.