Relationship between radiological knee osteoarthritis and biochemical markers of cartilage and bone degradation (urine CTX-II and NTX-I): the Matsudai Knee Osteoarthritis Survey

Biochemical markers of cartilage and bone degradation are becoming increasingly important in the evaluation of knee osteoarthritis (OA). To clarify the correlation between radiological knee OA and urine CTX-II (C-terminal crosslinking telopeptide of collagen type II) or urine NTX-I (N-terminal crosslinking telopeptide of type I collagen), we conducted a cross-sectional study in the cohorts of the epidemiological knee survey at the Matsudai district in Niigata Prefecture, Japan. Urine specimens were collected from 296 subjects, and CTX-II and NTX-I were measured using ELISA. Standing knee AP X-rays were obtained and graded according to the Kellgren-Lawrence classification. The subjects were then divided by gender, age (40- to 59-year-old group and 60- to 79-year-old group), and the X-ray grade (Grade 0, 1, Grade 2, and Grade 3, 4). In non-OA (Grade 0, 1) subjects, the 60- to 79-year-old group had significantly higher CTX-II values than the younger group only in females. The subjects of both genders aged over 60 years of age with OA Grade 3, 4 had significantly higher CTX-II values than the Grade 0, 1 group or the Grade 2 group. For NTX-I, there were no significant differences between each OA grade although the Grade 3, 4 group females from 60 to 79 years of age had higher values than the Grade 2 group. In addition, in the 60- to 79-year-old subjects of both genders, a positive correlation was observed between the urine CTX-II and urine NTX-I. For the subjects ranging from 60 to 79 years of age in both genders, the urine CTX-II values indicate the progression of OA. In addition, the weak but positive correlation between urine CTX-II and urine NTX-I in the subjects ranging from 60 to 79 years of age in both genders suggests that bone resorption and cartilage degradation appear to develop in parallel.