BGLAP and osteoarthritis: Moreover, several clinical ex/in vivo and in vitro studies have confirmed the presence of elevated alkaline phosphatase activity and increased osteocalcin levels in primary human osteoarthritis subchondral osteoblasts (Cantatore et al., 2004; Hilal et al., 1998, 2001; Mansell, Tarlton, & Bailey, 1997).