Osteoarthritis (OA) is the most common joint disease, causing severe pain due to joint inflammation (synovitis). While total knee arthroplasty (TKA) is commonly performed to reduce pain, 20% of patients are dissatisfied with their outcome post-surgery. This dissatisfaction is caused by persistent pain post-TKA due to synovitis that is not routinely removed during surgery. To address this problem, a synovectomy can be performed during TKA, which involves resecting the inflamed layer of tissue lining the joint, called the synovium, and its associated sensory nerve endings. Since the synovium will regenerate in the months post-surgery, synovectomy only transiently reduces pain after TKA. The proposed study will help ascertain the benefits and effects of synovectomy in patients who are more likely to experience poor satisfaction (driven mostly by pain) post-TKA. This study will include 62 patients undergoing TKA due to end-stage OA who have moderate to severe synovitis, as determined by ultrasound assessment. Patients will be randomized (1:1) to undergo a TKA with synovectomy or without synovectomy. Primary and secondary outcomes will be assessed through patient-reported levels of pain and function, results from physical performance tests, and quality of life (QOL) scores. These measures will be recorded pre- and post-surgery for comparison. Through demonstrating that synovectomy can at least transiently reduce pain post-TKA, this study will provide evidence for the development of medical therapies that target the synovium to slow its regrowth. This will be transformative for the long-term management of joint pain and synovitis post-surgery, thus significantly improving patients' overall QOL.