Can knee cartilage reveal why osteoarthritis worsens?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Osteoarthritis group: 1. Meets the American College of Rheumatology (ACR) diagnostic criteria for osteoarthritis: ① Persistent knee pain for ≥1 month; ② X-ray shows osteophytes at the knee joint margin; ③ Age ≥50 years; ④ Morning stiffness \<30 minutes; ⑤ Knee joint friction sounds. (Diagnosis requires item ① plus any two of items ②-⑤). 2. Radiographic Kellgren-Lawrence (K-L) grade ≥2; 3. Complete the entire treatment course without interruption or modification of the treatment plan during the process; 4. Complete the full-process assessment and follow-up; 5. The image and medical record materials are complete. Normal control group: Normal Control Group (subjects must meet criteria for one of the following two sources): (1) Source A - Non-arthritic surgery patients: 1)No history of knee osteoarthritis, rheumatoid arthritis, gouty arthritis, infectious arthritis, or other joint diseases 2)Undergoing surgery for one of the following indications: 1. Femoral neck fracture (Garden type I/II) treated with artificial femoral head replacement 2. Simple meniscus injury or ligament injury requiring knee arthroscopy 3)Preoperative X-ray of the joint from which cartilage will be collected shows normal joint space, K-L grade 0, and no osteophytes, subchondral sclerosis, or cystic change (hip joint for femoral head replacement; knee joint for arthroscopy) 3)Intraoperative macroscopic observation or specimen evaluation confirms smooth cartilage surface with no softening, fissure, or fibrosis (Outerbridge grade 0) 4)Complete imaging and medical records available Source B - Traumatic amputees: 1. No history of any joint disease (knee osteoarthritis, rheumatoid arthritis, gouty, infectious arthritis, etc.) 2. Undergoing amputation of a lower limb purely for traumatic reasons, with no pre-existing joint pathology in the limb to be amputated 3. Preoperative X-ray of the target joint (typically knee or hip) shows K-L grade 0 and no signs of osteoarthritis 4. Intraoperative macroscopic evaluation of the articular cartilage from the amputated limb confirms Outerbridge grade 0 (smooth, intact surface) 5. Complete imaging and medical records available Both sources: Signed informed consent for voluntary participation Exclusion Criteria: ① Combined with other types of joint diseases, autoimmune diseases or bone metabolic diseases; ② Has a history of drug abuse; ③ Those who have not signed the informed consent form; ④ Suffering from mental illness and unable to cooperate with research; ⑤ Other personnel who are not suitable to participate in the research.