This study conducts clinical experiments on the form, temperature, frequency and other issues of cooling therapy, so as to provide scientific evidence for the practice of cooling therapy and improve the comfort and effect of cooling therapy, so as to achieve the goal of improving service and patient experience proposed by the National Health Commission.

Knee osteoarthritis (KOA) is a degenerative joint disease that severely impacts patients' quality of life, primarily manifesting as knee pain and restricted mobility [1]. According to the Osteoarthritis Diagnosis and Treatment Guidelines (2018 Edition) [1], the prevalence of symptomatic knee osteoarthritis in China is 8.1%. Total knee arthroplasty (TKA) is primarily indicated for elderly patients with severe late-stage KOA-related pain and functional impairment. TKA not only improves knee function and corrects deformities but also significantly enhances patients' quality of life. Research by Feng et al. [2] demonstrates a rapid increase in TKA cases in China, rising from 53,880 cases in 2011 to 374,833 cases in 2019-a 5.9-fold growth. However, moderate to severe postoperative pain following TKA remains a major challenge, adversely affecting rehabilitation, patient satisfaction, and clinical outcomes .

Current postoperative pain management strategies for TKA include pharmacological and non-pharmacological interventions. While pharmacological approaches are relatively well-established and effective, they carry side effects such as nausea, vomiting, dizziness, and dependency. Non-pharmacological interventions include cold therapy, localized elastic bandage compression, limb elevation, and early rehabilitation exercises [5-7]. Cold therapy, a simple and cost-effective physical intervention, involves applying ice packs or cold water to reduce skin temperature, thereby decreasing local tissue metabolism, promoting vasoconstriction, reducing edema and hematoma formation, and slowing nerve conduction to alleviate pain. Additionally, cold therapy mitigates local inflammatory responses and blood loss, effectively improving pain and patient comfort .

Existing studies on cold therapy at varying temperatures for TKA are limited, with significant discrepancies in recommended application durations . Excessively low temperatures risk superficial or deep tissue frostbite, nerve damage, and even deep vein thrombosis or necrosis, while insufficient cooling may compromise analgesic and anti-inflammatory efficacy . Although cold therapy is widely adopted post-TKA, critical parameters-such as modality, temperature, frequency, and duration-remain controversial in clinical practice.

This study aims to address these unresolved issues through a clinical trial, generating scientific evidence to optimize cold therapy protocols. The findings will enhance patient comfort and therapeutic outcomes, aligning with the National Health Commission's goals of improving healthcare services and patient experiences.

Inclusion Criteria:

• Age ≥ 18 years after primary total knee arthroplasty
• No history of open injury or prior surgery in the affected knee

Exclusion Criteria:

• Motor, sensory, or cognitive dysfunction
• History of mental disorders
• Coagulation abnormalities
• Chronic use of oral corticosteroids (>3 months)
• Cold hypersensitivity/allergy
• Withdrawal due to non-study-related reasons
• Thyroid disease