A study of 221 patients found an association between low serum levels of vitamin D and decreased knee function in patients with osteoarthritis of the knee. All of the patients had knee arthritis and reported knee pain on many days in the month before they joined the study.
For the study, the researchers measured the blood levels of vitamin D at the start and again after 15 months and 30 months. Changes in vitamin D levels were compared with changes in knee pain, physical function, and muscle strength during the 30-month study. Lead investigator Kristin Baker, PhD, said that decreased levels were connected with higher levels of pain and disability and some muscle weakness.