WD 40 helping with arthritis has been used for years by many older people who claim that spraying WD 40 on your joints helps to relieve joint pain because of lubrication.
But there's no way that WD 40 can help your bodies joints through lubrication because when you spray the WD 40 on your skin it doesn't penetrate your skin where your joints are.
Arthritis is inflammation of your joints so WD 40 cannot help with the inflammation of your joints so no using WD 40 on your joints cannot help with arthritis.
My Grandma used to use WD 40 on her joints and said it worked but she was just thinking it worked and in reality there's no way for WD 40 can help.