Osteoarthritis (OA) is the most prevalent degenerative joint disease worldwide, which causes pain, loss of joint function and declined quality of life, and ranks as the leading cause of disability among individuals aged over 60 years. In China, the number of patients with osteoarthritis is projected to exceed 200 million by 2044, resulting in a continuously growing demand for medical resources and escalating economic burden.Nevertheless, the lack of effective biomarkers for early diagnosis leads to advanced disease conditions at the time of initial medical consultation and delayed treatment. This project intends to collect blood samples from OA patients and suspected patients in the orthopedic outpatient department of a tertiary hospital. Diagnostic and differential diagnostic tests will be adopted to verify the clinical application value of previously reported candidate biomarkers, so as to screen out biomarkers with favorable validity and reliability. The research findings are expected to provide data support and theoretical basis for the early prevention, early diagnosis and individualized intervention of osteoarthritis.

Osteoarthritis (OA), the most common degenerative joint disease worldwide, is witnessing an increasingly severe epidemiological trend in China driven by population aging and shifts in lifestyle. According to the Global Burden of Disease (GBD) data, the number of OA patients in China has risen from 26.1 million in 1990 to 61.2 million in 2019, ranking first globally, and is projected to exceed 200 million by 2044. The prevalence of OA increases markedly with age, affecting over 50% of individuals aged 65 years and older. Women exhibit a higher incidence than men, especially after menopause, and tend to suffer from more severe structural lesions and clinical symptoms. The knee joint is the most frequently affected site, followed by the hands, hips and other joints.

OA not only causes pain, loss of joint function and impaired quality of life, but also represents the leading cause of disability in the population aged over 60. In 2019, the age-standardized disability-adjusted life years (DALYs) of OA in China reached 224.78 per 100,000 population, a 9.4% increase compared with 1990. Notably, the disease burden of knee and hip OA related to elevated body mass index (BMI) has increased substantially in males, and the growth rate of DALYs attributable to high BMI is higher for hip OA than for knee OA. Meanwhile, the disease burden of hand OA is also on the rise among females.

Major risk factors for OA include advanced age, obesity, joint injury and occupational strain such as sedentary behavior and repetitive weight-bearing activities. Since the reform and opening-up, China has achieved rapid economic development and a remarkable extension in life expectancy. By the end of 2024, the population aged 65 and above had reached 220 million, accounting for 15.6% of the total population; life expectancy is expected to reach 81.3 years by 2035. In parallel, behavioral risk factors closely linked to OA, including a sedentary lifestyle, insufficient physical activity, unhealthy dietary patterns, elevated BMI, smoking and alcohol consumption, have become increasingly prevalent. Under the combined effect of population aging and unhealthy lifestyles, the incidence, prevalence and overall disease burden of OA are predicted to climb continuously. This places a heavy burden on the healthcare system and poses a major challenge to the achievement of the Healthy China Initiative.

Current clinical management of OA is confronted with two core bottlenecks. First, there is a scarcity of early diagnostic biomarkers and individualized prediction tools. Most patients seek medical care only after obvious symptoms emerge, by which time irreversible structural damage to joints has already developed. Second, OA is a highly heterogeneous disease. The pathogenesis of OA at different anatomical sites (knee, hip, hand, etc.) involves the complex interaction of multiple factors including mechanical overload, low-grade inflammation and metabolic disorders. Consequently, there are currently no effective therapies capable of reversing disease progression, and clinical interventions remain limited to symptomatic relief.

Accordingly, the establishment of a specialized OA cohort is of critical importance. By systematically collecting high-risk factors, clinical phenotypes, imaging findings, biological specimens (blood, synovial fluid, joint tissue, etc.) and multi-omics data, the specialized cohort will facilitate precision prevention and treatment of OA in the following aspects: 1. Identification of novel biomarkers for early diagnosis and prognostic evaluation; 2. Construction of artificial intelligence-assisted individualized diagnosis and prediction models, which integrate multidimensional data to realize early disease warning, progression risk stratification and treatment response prediction.

Inclusion Criteria:

1. Aged between 40 and 70 years (inclusive);
2. Joint pain or stiffness lasting for no less than 3 months;
3. Voluntary participation with signed informed consent.

Exclusion Criteria:

1. Combined with other severe joint diseases, such as rheumatoid arthritis, gout, etc.;
2. Suffering from severe systemic diseases, such as heart failure, malignant tumors and others;
3. Received joint surgery within the past 3 months or taking medications that may affect the progression of osteoarthritis;
4. Individuals with cognitive dysfunction who are unable to cooperate with the research procedures;
5. Failure to complete X-ray, MRI examination or follow-up visits as required.

The study subjects shall include patients with osteoarthritis (OA) at different anatomical sites as far as possible, such as the knee, hip and hand. Enrollment will focus on early-stage OA patients with Kellgren-Lawrence (K-L) grade 1-2. Meanwhile, patients with diseases that share similar clinical manifestations with OA and are prone to misdiagnosis shall also be enrolled.