Can Melatonin cause/increase joint pain?

This is far, far, more likely to be due to some other condition or to conditions which are known advancing. Melatonin is a natural compound that the body creates on its own, just not enough of it as we age. Assuming the formulation you are administering is a safe one without added fillers or whatever that could be causing the discomfort, it won't be the melatonin itself.

Since posting this question, I have learned that Melatonin is a risk for individuals with autoimmune conditions because it stimulates the immune system. When searching with the two words (melatonin and autoimmune) together, information pertaining to the risks can be found. There are also posts about the risks in the PMR group on this Mayo Connect site. Hope this helps others who may have this same question.

Melatonin is pleiotropic showing more effects than sleep and biological clock regulation.
It is effective in reducing some inflammatory cytokines. There is
some old literature saying it might interfere with prednisone but the source is dubious and not documented. More likely to lessen joint inflammation.

Side Effects of Melatonin

Short-term use of melatonin may cause mild side effects, including:

Headaches
Dizziness
Nausea
Drowsiness
Less common side effects include:

Short-term feelings of depression
Mild tremor
Mild anxiety
Abdominal cramps
Irritability
Reduced alertness
Confusion or disorientation
Source: Mayo Clinic

@wellnesswins If your mom complains about aching joints, you could try plain Tylenol. Just tell her that it should help her to relax and help with sore knees. I take it and it really helps me get to sleep!

@becsbuddy
Have you used the arthritis version of Tylenol?

@wellnesswins I don’t think so. I’ve seen it in the stores but it was always extra strength so . . . .