Objective:To explore the early clinical efficacy of ultrasound visualized platelet-rich plasma (PRP) in the treatment of lower back myofascial pain syndrome (MPS) after sports injury.Methods:A prospective cohort study was conducted to analyze the clinical data of 32 patients with lower back MPS after sports injury, who were admitted to West China Hospital of Sichuan University from January 2023 to March 2023. Ultrasound-guided PRP injection into the erector spinalis or quadratus psoas muscles was used for treatment. Before treatment, at 24 hours, 2 weeks, and 4 weeks after treatment, pain and function were evaluated using visual analogue scale (VAS), McGill pain questionnaire (McGill), Roland Morris dysfunction questionnaire (RMDQ), and Oswestry dysfunction index (ODI). Before treatment and 4 weeks after treatment, the quality of life was evaluated using the short-form 36 item health survey questionnaire (SF-36). The adverse reactions were observed during treatment and follow-up.Results:A total of 32 patients with lower back MPS after sports injury were enrolled, including 10 males and 22 females; aged 12-68 years [(47.3±16.3)years]. All the patients were followed up for 4 weeks. Before and at 24 hours, 2 weeks, and 4 weeks after treatment, the VAS was 5.0(4.0, 6.0)points, 3.5(3.0, 4.8)points, 2.0(2.0, 3.0)points, and 2.0(1.3, 3.0)points, respectively; the McGill score was 9.0(7.0, 11.0)points, 7.0(5.0, 9.0)points, 4.0(3.0, 5.0)points, and 3.0(3.0, 5.0)points, respectively; the RMDQ score was 8.0(5.3, 10.8)points, 5.5(3.0, 8.0)points, 4.0(3.0, 5.8)points, and 3.0(2.0, 4.8)points, respectively; the ODI was 22.0(14.5, 30.0), 20.0(14.5, 25.5), 9.0(6.0, 16.0), and 8.0(4.5, 14.0), respectively. Compared with the values before treatment, the VAS, McGill score, and RMDQ score were significantly decreased at 24 hours, 2 weeks, and 4 weeks after treatment (all P<0.05); the ODI had no significant difference at 24 hours after treatment ( P>0.05), but it was significantly decreased at 2 and 4 weeks after treatment (all P<0.05). Compared with the values at 24 hours after treatment, the VAS, McGill score, RMDQ score and ODI further decreased at 2 weeks after treatment (all P<0.05). Compared with the values at 2 weeks after treatment, there was no significant difference in the VAS, McGill score, RMDQ score, or ODI at 4 weeks after treatment (all P>0.05). In the SF-36, the scores of physiological function [77.5(60.0, 93.8)points], physiological role [50.0(0.0, 100.0)points], body pain [64.0(44.5, 74.0)points], vitality [75.0(65.0, 78.8)points], social function [87.5(75.0, 100.0)points], emotional role [66.7(33.3, 100.0)points] and mental health [72.0(68.0, 83.0)points] before treatment were increased to 90.0(80.0, 98.8)points, 100.0(56.3, 100.0)points, 84.0(74.0, 84.0)points, 75.0(70.0, 80.0)points, 100.0(87.5, 112.5)points, 100.0(66.7, 100.0)points, and 76.0(68.0, 84.0)points after 4 weeks of treatment, respectively ( P<0.05 or 0.01). However, there was no significant difference in the general health status or health changes before and after treatment (all P>0.05). During treatment and follow-up, no adverse reactions such as redness, swelling, pain, or subcutaneous bleeding were observed. Conclusion:Ultrasound-guided PRP treatment can improve the early pain, lumbar mobility and quality of life of patients with lower back MPS after sports injury, with no presence of adverse reactions.