Is there a link between Parkinson's disease and osteoporosis?

Possibly. The association would be parkinsons patient are limited in mobility which will decrease bone mass. Also dietary deficiencies in parkinsons patients can lead to further bone loss. In 2009 italian researchers found that osteoporosis and osteopenia ocurr in 91% and 61 % in women and men respectively.
Parkinsons & bones. Yes. Osteoporosis and osteopenia are very common findings in patients with parkinson's disease, affecting up to 91% of women and 61% of men. Reduced bone mass in parkinsonian patients seems to be caused mainly by reduced mobility through a mechanism similar to that observed in other neurological diseases. See http://www.Ncbi.Nlm.Nih.Gov/pubmed/19346153.