I just turned 41 (on the 18th of January actually) and i have had osteoporosis for 3 years. Have you had a hysterectomy or have low estrogen? Both can cause bone loss and early osteo. Until you find out try calcium and vitamin D.
Nothing surprises me. I ignorantly thought that osteo/rheumatoid arthritis as well as osteoporosis happened at a much older age and i have all three but if you read through this forum most people are around our age and younger.
Just so I don't misunderstand you did say osteoporosis, not osteoarthritis. And yes having a complete hysterectomy without Hormone replacement therapy can definitely cause bone loss and osteoporosis. My oncologist first recommended Calcium and Vitamin D but after my last Bone density mineral test I started taking Actonel 1 x week which is supposed to help replace bone loss. I am not a doctor though, but ask him just to see what he says.
They are even going as far as saying that my Rheumatoid arthritis may be caused by the quick onset of menopause (change in hormone levels).