Aim: The aim of this study was to assess whether BMI, severity of knee osteoarthritis, age and gender have any influence on the final clinical results of bone marrow aspirate concentrate injection. Method: A total of 111 study participants with painful knee osteoarthritis and different characteristics concerning before mentioned factors underwent bone marrow aspirate concentrate (BMAC) therapy and were followed up for 1 year. Result: Significant pain and functional improvement were observed in all participant groups. Participants' age and BMI did not influence the clinical outcome, but there was an influence of OA severity, especially among older patients. Conclusion: This study shows that BMAC therapy is effective. Younger patients with milder OA changes could be better candidates for long-lasting and more efficient BMAC therapy. Clinical Trial Registration: NCT03825133 (ClinicalTrials.gov).