This is a single-center retrospective cohort study to identify independent risk factors and develop a predictive nomogram for moderate-to-severe pain within 24 hours after Achilles tendon surgery.

Inclusion Criteria:

1. Age ≥ 18 years; American Society of Anesthesiologists (ASA) physical status classification Ⅰ~Ⅲ;
2. Clinically diagnosed with Achilles tendon rupture, Achilles tendinopathy, insertional Achilles tendinitis, Haglund's deformity, or other Achilles tendon disorders;
3. Undergoing open or arthroscopic Achilles tendon surgery;
4. Conscious and able to cooperate in surgery and postoperative pain assessment;
5. Complete and accessible case data related to surgery, anesthesia, and postoperative pain assessment;
6. Completion of at least 24 hours of standardized pain monitoring and clinical follow-up after surgery

Exclusion Criteria:

1. Missing or incomplete key clinical data such as pain assessment, surgery and anesthesia;
2. Failure to complete 24-hour standardized pain monitoring after surgery; Perioperative unplanned secondary surgery or transfer to the intensive care unit (ICU);
3. Patients with mental illness, cognitive dysfunction, or language communication barrier; History of alcohol or drug addiction Pain due to other acute or chronic diseases;
4. Bilateral Achilles tendon surgery Concurrent surgery for other lower extremity injuries

The study population consists of adult patients (≥18 years) who underwent Achilles tendon surgery at Peking University Third Hospital between January 2020 and December 2024. Eligible patients were those with complete perioperative data and standardized 24-hour postoperative pain assessments, meeting all inclusion and exclusion criteria of the study.