The need for improved analytical techniques in the study of slow, degenerative diseases such as rheumatoid arthritis and osteoarthritis has driven major efforts aimed at identifying biochemical markers of pathological processes in both diseases. A series of novel biochemical markers has surfaced and their careful validation has become a critical requirement for further use in clinical research. This report aims at providing a critical review of biochemical markers applied in clinical research of joint diseases, in particular those markers reflecting the turnover of cartilage tissue