Quick question for my own edification. Have you ever had a back injury in the area of the Arthritis? It doesn't even have to be major, just a pull or sloppy rep that caused some noticeable lasting pain? And how did you deal with it?
Im not a big fan of listening to the average "professional" when it comes to this stuff because most of them have a very narrow view of this type of thing and dont understand the complete picture. What I would do personally is go about my life and lift performing anything I used to do doesn't cause lasting pain. You will have to be the judge of what that is.
Just to elaborate on why I asked my initial questions, long term permanent damage of this type is usually due to a culmination of things. Nutrition AND an injury that wasn't allowed to heal. This can happen in the spine or just about any joint, spine and shoulders being most common.
Athletes have a tendency to rely on the doctor recommended RICE method of dealing with an injury, rest, ice, compression and elevation almost always accompanied by large doses on anti-inflammatories. All of these squash inflammation which is an essential part of the healing cascade (google for references). This immediate treatment does a good job of alleviating the pain but it that doesn't mean the underlying problem is healed. However, no pain means you hit the gym or back to your regularly scheduled activities and you continue to cause damage to an already weakened joint. The culprit is usually tendon/ligament damage which takes months to heal under normal circumstances and if RICE and anti-inflammatories are used often will NEVER heal completely without aid. These strained tendons/ligaments cause joint laxity which often times the muscle will try and account for by maintaining some form of contraction to help stabilize the joint. Not as noticeable in the shoulder or elsewhere but in the spine, this often leads to cramps and a lot of muscle tension which in and of itself, over time can pull things out of whack. Over time if not allowed to heal the slop in the joint can cause uneven wear on the cartilage and other smooth surfaces between the bones and uneven pressure and bulges or ruptures in the discs of the spine. To rectify this calcium often builds to take the place of the damaged soft tissue and as a last resort to restore some stability to the joint.
The other aspect is nutritional. Without proper nutrients, the calcification of soft tissue can occur. Vit K, along with A and D are essential for the proper use of calcium, without the proper nutrients calcium can't be properly used and end up getting misused (stored). Tendons/ligaments are collagen based tissue and athletes while putting large demands on their body also often don't get much in the way of vitamin C which is an often overlooked part of collagen synthesis. Couple interrupting the healing cascade with low levels of nutrients needed for repair and over time permanent damage manifests.
It's important to remember modern medicine doesn't heal people. It uses surgery to rebuild/repair if it can, and can often time do amazing things, but the typical doc doesn't treat your condition or underlying disease, they simply seek to control and treat the symptoms. So when a doc recommends RICE and anti-inflammatories they are treating the symptoms of your injury (ie the pain and visible swelling) they dont actually treat the problem itself and you as a patient suffer for it in the long run.