Thank you for the additional information, Ken.
First things first, what Maggie is experiencing is entirely normal for her age and breed. Labs tend to have hip and sometimes even knee issues as they age. Hip dysplasia is not uncommon either. To help combat some of the pain that goes along with arthritis, veterinarians often prescribe an anti-inflammatory regimen with or without the addition of medication to help reduce pain directly. Most veterinarians use one of the following medications as an NSAID:
Of the three, Rimadyl and Deramaxx are pet-only medications. All three of them are prescriptions but Meloxicam is marketed both for pets and for people. Some veterinarians prefer to use a pet-specific medication, but I've also seen quite a few of them using Mobic (human pharmacy Meloxicam). By and large, however, the most commonly used is Rimadyl. The first two medications come in a flavored chew that most dogs like and will take readily. Deramaxx remains quite pricy, but Rimadyl and Mobic are pretty inexpensive if you price shop.
If NSAIDs alone don't give Maggie the relief that you seek (and believe me, most people report their companion going back to a "puppy like" state when they finally get relief of their discomfort), your vet may wish to add a medication or two for chronic pain. These are usually "end stage" cases where the discomfort has become so bad that there's no other option. The vast majority of cases don't require this, but it's worth mentioning since we don't know just how bad Maggie is feeling (it could be something that is fixed with an NSAID or it could be something that requires more). The most common medications to be prescribed for this are:
These medications are marketed from the human side of medication, as you'll find to be the case with quite a few medications we use in pets, but they're also rather reasonably priced because a lot of people with chronic pain use them as well. If need be, compounding pharmacies can make these into palatable chews, although I've seldom found a lab to turn their nose up at a small hunk of cheese with a pill inside :)
You'd also mentioned that Maggie has a bunch of lumps on her side. Through the computer, of course, it's nearly impossible to tell you exactly what these are but my suspicion is that they're lipomas. In fact, if ever there was a 'poster child' breed for lipomas, retrievers would be it. Lipomas are literally just bulky fatty tissue under the skin. They look much worse than they are. They can range in size from a pea all the way up to a basketball or larger. We usually don't remove them unless they begin to hinder a pet's ability to get around. If these are out of the way and not causing Maggie much concern, there's no real reason to put her under the risk associated with anesthesia in order to remove something that isn't bothering her. The next time she's in to see her vet, I'd recommend talking to your vet about these to be sure that's what they are. In any case, if they change in size or shape rapidly, open, begin to ooze, etc. she's going to need to be examined beforehand. Until then, just keep an eye out.
There's more info on Lipomas here: https://www.vetinfo.com/managing-lipomas-dogs.html
Let me know if there's anything else I can help you with today. I hope Maggie is on her way to feeling well quickly. Medications such as these work quite quickly and I'm confident they will allow her the ability to get into the proper position to go to the bathroom naturally as she has her entire life up until this point.