Collagen?

My friend recommended I try collagen to help lessen my joint pain. I’ve only ever heard of collagen being used for hair, skin, and nails. Has anyone else been recommended collagen by a doctor or maybe pharmacist? I’ve been told not to take any supplements or vitamins unless a provider says I have an deficientancy (sp?) I’ve actually tried collagen in the past since I wash my hands often which makes my nails weaker, so it def worked for my nails, but I don’t remember it even doing anything else for like hair, skin, pain relief, etc. I only tried it cause it was discounted heavily so I could afford it. Supplements are expensive.