We aimed to find out that whether collagen turnover is altered in the context of Legg–Calve–Perthes disease (LCPD) by evaluating serum prolidase activity. We also investigated the correlation between collagen turnover and oxidative–antioxidative status in LCPD. Plasma prolidase activity, total oxidant status (TOS), total antioxidant capacity, and oxidative stress index (OSI) were determined for 39 patients with LCPD and 40 healthy controls. Serum prolidase activity, TOS, and OSI were higher, but TAC was lower in patients with LCPD compared with controls. Prolidase activity was positively correlated with TOS and OSI levels. Serum prolidase activity is significantly associated with LCPD.