To investigate the correlation between the degree of knee cartilage damage observed by knee arthroscopy and bone metabolism markers, in order to provide a clinical theoretical basis for early identification of high-risk groups for knee osteoarthritis (KOA) and the formulation of individualized KOA prevention and treatment strategies.

A total of 156 patients who needed arthroscopic knee surgery at the department of spinal joint surgery, Shengjing Hospital Affiliated with China Medical University were analyzed retrospectively from January 2021 to December 2023, exclusion criteria comprised inflammatory arthropathies, history of knee surgery and significant knee trauma. According to the Outerbridge classification of the degree of knee cartilage injury observed in knee arthroscopy, the subjects were divided into four groups according to the grade of injuries. Various factors, including bone metabolism markers such as 25-hydroxyvitamin D (25-OH-VD), parathyroid hormone (PTH), β-collagen degradation products (β-CTX), N-terminal osteocalcin (N-MID), total type I collagen amino-terminal extension peptide (TP1NP), as well as gender, age, body mass index (BMI), bone mineral density, meniscus injury, and cruciate ligament injury were analyzed. The general data difference analysis was carried out and the statistically significant variables were included in the univariate multivariate ordered logistic regression model one by one. The indicators with statistically significant differences were further selected and included in the multivariable ordinal logistic regression model for analysis, so as to explore the correlation between each factor and the degree of knee cartilage injury.

The results of the analysis of the differences in general data showed that there were statistical differences in age, BMI, T value of bone density, 25-OH-VD, β-CTX, N-MID, TP1NP and whether there was meniscus injury or not in the four groups (all P<0.05). The results of multifactorial orderly and multiclassified logistic regression analysis showed that age increase [odds ratio (OR)=1.067, P<0.01], BMI increase (OR=1.198, P<0.05) and meniscus injury (OR=3.697, P<0.05) are Independent risk factors for the degree of knee cartilage injury (P< 0.05), while large bone density T value (OR=0.252, P<0.001) 、higher levels of 25-OH-VD (OR=0.937, P<0.05) and N-MID (OR=0.881, P<0.001) are independent protective factors for the degree of knee cartilage injury.

Higher levels of 25-OH-VD and N-MID, as well as better bone density have a certain protective effect on knee articular cartilage, thus maintaining normal bone mass and normal levels of 25-OH-VD and N-MID can help protecting the articular cartilage of knee and postpone the occurrence and development of KOA. Knee cartilage injury tends to gradually worsen with the increase of age and BMI, and meniscus injury is an independent risk factor for knee cartilage injury.