A sailor's life is constant, never stopping. It's hard work, but it's worth it. There's a reason why the phrase 'old sea dog' exists. Those that spend their life on the seas and then decide to retire to the land often find a lifetime of hard labour catches up with them fast. So, most just keep sailing until they die.
Description & CauseA sailor's diet isn't the best. Sailors on trade Ships sometimes get gifted a small amount of exotic foods but otherwise, for cost purposes the diet is limited. In fact, some even rely on people capable of conjuring rudimentary food and water and operate on the bare minimum. Nutritionally, it's functional but it's hardly the best to live a life on. As sailors reach their twilight years, it is common that their bones will be significantly weaker due to this. They will find physical activity harder. Strictly speaking, they will be able to lift and carry almost as well since that is mostly muscle-based, but come the end of the day they will feel the ache in their bones. Naturally, older sailors tend to have reached the higher positions upon the ship so the need for strenuous exercise has waned. That said, even the top roles are active positions and particularly chronic cases of Sailor's Bones will find continuing aboard the ship difficult.
TreatmentThe Surgeon aboard the ship may often be a cleric with divine magic, but even so, that is not an effective way to combat Sailor's Bones. There is no way, in fact. Low-level restoration magic can slow the effects over time, but a cleric's magical ability is limited and would not be used in this way in case of emergency. Sufferers of Sailor's Bones will typically find themselves adhered to the adage of 'it's easier to keep going than to stop and get going again' and stubbornly continue to soldier on in their role. Very few sailors who suffer will decide to retire to the land permanently. Something about the exercise and sea air seems to make it easier for them to continue.