Osteoarthritis (OA) is a progressive degeneration of articular cartilage leading to failure in functional mobility of joints. It is characterized by morphological, biochemical and molecular changes in histology of cartilage. Different biological markers are used as indicators to precisely predict the stage of cartilage destruction of joints in OA patients and to evaluate the therapeutic efficacy of drugs used for OA. The present research was chalked out to establish relationship between disease activity and serum level of C-terminal telopeptide of type II collagen (CTX-II) in experimentally induced OA rat model. Out of 30 male Wistar rats, 25 were used to induce OA by injecting papain (10mg/0.5mL of 0.05M sodium acetate) in right knee joints whereas five (control) were injected with sterile normal saline solution on day 0. Blood samples (5mL each) were collected on weekly basis up to 28^th days of post papain injection. Sera were separated and subjected to perform ELISA for estimating CTX-II fragments as cartilage biomarker (CartiLaps ® ELISA kit) in experimental groups. Maximum level of CTX–II (pg/mL) (40.44±3.07) was observed in sera samples of day 14 post papain injection followed by days 21 (40.22±2.01), 28 (36.82±3.81), 7 (34.48±4.17), 1 (15.08±4.22) and day 0 (2.55±0.10). The early changes in serum CTX-II from day 0 to 14 showed significant association with cartilage damage. Later on, no significant difference was observed in CTX-II level on day 14, 21 and 28 post papain injection. It is concluded that elevation in serum CTX-II level was concomitant with the onset of disease and degradation of cartilage. Moreover, CTX-II is a sensitive diagnostic biomarker to monitor joint disorder severity in papain induced OA rat experimental model on different days. These findings may be used as base line for early diagnosis of disease and initiation of therapy for successful outcome.

Key words: Articular cartilage, CTX-II, ELISA, Osteoarthritis, Papain