Brittlebone
Brittlebone is perhaps one of the more normal things that happen to someone when they grow old. Although the name points at one of the symptoms, Brittleboke includes several bone-related things that happen to someone as they grow old. It's so widespread it's in fact impossible to grow old without getting Brittlebone in some form or another.
Brittle Bones
This symptom is in the name of the condition. The person's bones get brittle with age and more prone to breaking. Falling over is risky as the fall might cause broken bones. The bones are also slower to heal, making a broken leg into a potential risk to not be able to walk again.
Bending Back
The spine will curl forward, giving the person a forward bent position. It will also become slightly shorter, which means the person will have a decreased height.
Stiffer Joints
The joints will become stiffer, making the person less dexterous and making it harder to move. Joint pain is a common symptom as well.
Prevention and Treatment
It is thought that some foods might lessen the chance of getting Brittlebone early, and possibly lessen the severity of symptoms after getting the condition. Physical exercise might help slowing down the process as well. None of these are completely proven, and doesn't work on everyone, but some might have a slight positive effect.
Most treatment is centered around giving pain relief for joints.
Hi Milladamen, it's me, the friendly worldbuilding wizard who is at D&D right now (don't tell my DM lol). I'm pretty sure this is just arthritis, but I like how it affects the people in your world differently depending on their culture. Because that's what you do with an article about a disease everyone knows: you show how the people of your world react to it. I'm not a big fan of the sidebar holding all of that info though. Try using the three columns to separate them out in the main text. You can always put an image or expand on treatment info in the sidebar. Alright, I'll see you around. See you :D