Small plug or whole joint, it should work with the same enzymes, depends how much damage you want to do to the knee, optimize the digestion time

I assume you intend to do that in vitro. You can just scale up from a single plug to a whole joint surface, the protocols will work, but you might need quite an amount of enzymes. You want to check if scaling up the concentrations from the plug level to the whole joint surface is economically feasible before you start. Do you really need the whole joint for an in vitro study tat anyways only "simulates" the effects of OA but is not authentic OA?

I need to enzymatically digest the  entire porcine acetabulum, different digestions will be used which will ultimately create different grades of OA. 

I need to see the effect of each material implant (ceramic, polymer,..) on the actual joint which is OA like. We have previously done that on the cartilage plugs, (both biomechanical and enzymatically OA induced). I have never done enzymatic digestion before that is why I was concerned whether the protocol will be different for a bigger scale as the number of cells will be higher. 

Just estimate the total volume of cartilage and scale the volume of solution it needs to be immersed accordingly - rule of thumb is the solution needs to be 10x the volume of the cartilage - and leave only the cartilage immersed, minimize the bone component.

Estimate the costs for that for the number of tests you need to perform. It might actually be cheaper or equally expensive (and more interesting from a scientific/publication point of view) to do the test in an animal model directly in which you induce OA. Rabbits would be good, although surgery is a little difficult, and minipigs where surgery is easier (they are a bit bigger).