We present evidence of kinematic and functional improvements of the trigger digit after sonographically assisted percutaneous release using quantitative motion analyses and functional assessments, respectively. Twenty-two patients with idiopathic trigger digits, who received the surgery, were recruited. A motion tracking system was used to measure the assigned kinematics parameters at the presurgical visit and at 1, 4, and 12 weeks after surgery. The hand strength and functional outcome were also obtained using dynamometer and self-report questionnaire assessments. The hand strength, maximal workspace, and joint range of motion of the involved digit were significantly smaller than that of the intact finger on the contralateral hand before surgery. The triggering phenomenon of the involved digit was significantly higher than that of the corresponding finger in the intact hand using a subscribed angular acceleration factor. The repeated measures showed that the workspace, joint range of motion, hand strength, and triggering effect of the involved hand significantly improved in follow-up examinations after the surgical intervention. Painful movement or insufficient tendon excursion of the trigger digit can cause loss of movement and strength, thus interfering with functional performance. After the disappearance of the pain and triggering by sonographically assisted percutaneous release, improvements in kinematics and function were objectively quantified in this study.