PROJECT SUMMARY Total knee arthroplasty (TKA) is a widely-performed surgical procedure to treat disabling knee conditions, but approximately half of all TKA patients experience moderate to severe pain during the critical first 4 weeks after TKA that can interfere with rehabilitation. Patients who are unable to engage fully in rehabilitation during this period risk substantial delays in return to normal function, reduced independence and quality of life, and have increased risk of developing chronic pain. Despite use of multimodal pain management, many patients still experience significant pain and require opioids that are associated with debilitating side effects, interfering with rehabilitation and delaying recovery during the critical first 4 weeks after TKA. The previous Phase I and II studies were successfully completed, demonstrating that percutaneous peripheral nerve stimulation (PNS) can provide immediate improvements in postoperative pain and knee mobility and produces greater relief of postoperative pain and improved function compared to standard of care alone during the first 4 weeks following TKA, resulting in lower incidence of chronic postoperative pain and opioid use at 3 months following TKA. The goal of the present Phase IIB project is to develop and test an advanced percutaneous PNS system that can: translate into routine clinical practice the benefits demonstrated in the previous Phase I and II clinical studies, overcome the challenges documented in these studies, and meet the design requirements to be deployed consistently and successfully by physicians with a wide range of skill sets in anesthetized patients before surgery to treat postoperative pain consistently throughout the critical postoperative 4-week rehabilitation window without the limitations of the existing standard of care. The project aims are to develop and test a multi- contact open-coil lead designed to widen the target area in which the lead can be placed using only anatomical landmarks and ultrasound guidance, avoiding the need to test stimulation and assess patient feedback (Aim 1); develop and test a unified introducer and connector system to enable a single physician to quickly and accurately deploy the lead followed by the lead connector without assistance (Aim 2); develop and test the external pulse generator, cabling, and user interfaces to complete development of the system (Aim 3); and determine if the proposed system enables quick and accurate lead placement in a clinical study (Aim 4). Successful completion of the aims will result in a novel percutaneous PNS system that is ready for submission for FDA 510(k) clearance, with a goal of providing in diverse healthcare settings the same pain relief, opioid reduction, and functional improvements demonstrated in previous studies in expert research settings. Commercialization of this innovative PNS system will substantially impact clinical practice by providing physicians and their patients with a non-op...