Background Tourniquet use during total knee arthroplasty (TKA) improves visibility and reduces intraoperative blood loss. However, tourniquet use may also have a negative impact on early recovery of muscle strength and lower extremity function after TKA. Questions/purposes The purpose of this study was (1) to determine whether tourniquet use affects recovery of quadriceps strength (primary outcome) during the first 3 postoperative months; and (2) to examine the effects of tourniquet application on secondary outcomes: voluntary quadriceps activation, hamstring strength, unilateral limb balance as well as the effect on operative time and blood loss.Methods Twenty-eight patients (mean age 62 ± 6 years; 16 men) undergoing same-day bilateral TKA (56 lower extremities) were enrolled in a prospective, randomized study. Subjects were randomized to receive a tourniquetassisted knee arthroplasty on one lower extremity while the contralateral limb underwent knee arthroplasty without extended tourniquet use. In the former group, the tourniquet was inflated just before the incision was made and released after cementation; in the latter group, a tourniquet was not used (10 of 28 [36%]) or inflated only during component cementation (18 of 28 [64%]). The choice of no tourniquet or use just during cementation was based on surgeon choice, because some surgeons felt a tourniquet during cementation was necessary to achieve a dry surgical field to maximize cement fixation. A median parapatellar approach and the One or more of the authors (DAD, CCY, TMM, RHK) has received funding from Porter Adventist Hospital, during the study period, in the amount of USD 10,000 to USD 100,000. One of the authors (DAD) has or may receive payments or benefits from DePuy (Warsaw, IN, USA) in the amount of USD more than USD 1,000,001 not related to this work. One of the authors certifies that he (RHK) has or may receive payments or benefits from Stryker (Kalamazoo, MI, USA) and Innomed (Savannah, GA, USA) in the amount of USD 100,001 to USD 1,000,001 not related to this work. One of the authors (TMM) has or may receive payments or benefits from Zimmer (Warsaw, IN, USA) in the amount of less than USD 10,000 not related to this work. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research 1 editors and board members are on file with the publication and can be viewed on request. Clinical Orthopaedics and Related Research 1 neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDAapproval status, of any drug or device prior to clinical use. Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.The surgeries for this study were performed at Porter Adventist Hospital, Denver, CO, USA, and the postoperative patient te...