Background: Bone fractures are a common cause of hospital admission. Currently, treatment consists of conservative regimens or operation. However, regenerative medicine introduces a possible new addition to established treatments. Evidence suggests that application of autologous mesenchymal stem cells can enhance bone regeneration, by differentiating into osteoblasts. This study investigates whether mesenchymal stem cells, isolated from bone marrow in sites of trauma or osteoarthritis, exhibit reduced proliferation and osteogenic differentiation in-vitro, compared to stem cells isolated from non-traumatic and non-osteoarthritic sites. If these pathologies are detrimental to the quality, clinicians should prioritize bone marrow from unafflicted sites. Methods: 17 patients were enrolled. 7 had recent unilateral trauma to the knee, requiring arthroscopy. 10 had x-ray verified unilateral osteoarthritis of the knee and were scheduled for arthroplasty. Stem cells were isolated from bone marrow aspirated perioperatively from both distal femurs. In-vitro osteogenic activity was assessed through alkaline phosphatase measurement, RNA-expression and alizarin red staining. Proliferation was measured using a growth curve. Results: 29 out of 34 primary cultures were successful, forming colonies with characteristic stem cell-morphology. There was no difference in mononuclear cell yield of aspirates or stem cell-yield from primary culture between non-osteoarthritic and arthritic knees or non-traumatic and traumatic knees. There was no significant difference in in-vitro osteogenic capability or proliferation. Conclusion: Our findings suggest that stem cells from sites afflicted by osteoarthritis or trauma can be utilized for bone regeneration with identical results as MSCs isolated from non-traumatic and non-osteoarthritic sites. However, clinical studies are needed to confirm this assumption.