Objective To study the safety and effectiveness of arc edge needle therapy for moderate to severe tenosynovitis of the flexor digitorum tendon in the thumb.Methods A total of 62 patients with moderate to severe stenosing tenosynovitis of the flexor digitorum thumb who met the inclusion criteria were collected.The patients were randomly assigned 1:1 to the arc edge needle group and the needle knife group using a random number table method.Among them,31 patients in the arc edge needle group were treated with arc edge needles,while 31 patients in the needle knife group were treated with traditional needle knife release surgery.Both groups were treated once.Record the number rating scale(NRS),range of motion(ROM),Quinell grade,and disease efficacy score(WDES)of patients before and after treatment at various stages(1 week,2 weeks,4 weeks),and at follow-up after 24 weeks to evaluate the treatment effect.Results During the 24 weeks follow-up of 62 patients after treatment,the Quinell grading comparison between the two groups showed that the arc edge needle group was better than the needle knife group(P<0.05);The total effective rate of disease efficacy score(WDES)was 96.77%in the arc edge needle group and 83.87%in the needle knife group.The clinical total effective rate of the arc edge needle group was better than that of the needle knife group(P<0.05);After treatment,both groups showed significant improvement in pain numerical score(NRS)and joint range of motion(ROM),and the degree of improvement increased over time(P<0.05);And the inter group comparison at 1 week,2 weeks,4 weeks and 24 weeks time points after treatment showed that the curved blade needle was superior to the needle knife group in improving pain and joint mobility(P<0.05).Conclusion Both the 45° tenosynovitis incision and release surgery with arc edge needle and traditional needle knife release surgery are effective in treating moderate to severe tenosynovitis of the thumb flexor digitorum tendon.However,the 45° tenosynovitis incision and release surgery with arc edge needle has significant advantages in improving pain,interphalangeal joint mobility,and safety.