We read with great interest the recent study by DeClaire et al [1] on liposomal bupivacaine (LB; EXPAREL, bupivacaine liposome injectable suspension; Pacira Pharmaceuticals, Inc, Parsippany, NJ) for total knee arthroplasty (TKA). We agree that managing postsurgical pain is critical to patient recovery and relying on opioids is suboptimal, due to not only opioid-related adverse events but also the risk that short-term exposure can lead to chronic use [2e5]. We also agree that local infiltration is important to multimodal analgesia, which can reduce the need for opioids, and that the duration of traditional local anesthetics does not match the duration of acute postsurgical pain.Although some orthopedic surgeons support the use of "pain cocktails" combining local anesthetics, nonsteroidal antiinflammatory drugs, opioids, corticosteroids, and other medications (eg, clonidine), the evidence supporting them is difficult to interpret because the ingredients and doses vary, other interventions (eg, nerve block) are often coadministered, studies do not always use validated outcomes, and their designs can be prone to bias and confounding [6,7]. Furthermore, the use of combination products that are not approved by the US Food and Drug Administration for this use is problematic for a variety of reasons (eg, availability, preparation, sterility, stability, compatibility, dosing), and LB remains the only medication approved by the US Food and Drug Administration for single-dose administration into the surgical site to provide up to 72 hours of postsurgical analgesia.As is common with many healthcare innovations, a certain learning curve is required with LB, and its efficacy can be affected by the amount used, admixture with bupivacaine and saline, and the location and number of injection sites used. For example, although early studies on LB for TKA used only 60 mL (20 mL LB and 40 mL saline), a recently completed phase 4 study (NCT02713490) used 120 mL (20 mL LB, 20 mL bupivacaine 0.5%, and 80 mL saline) [8,9].The protocol for this multicenter phase 4 study with 16 academic and community hospitals and dozens of orthopedic surgeons was published in 2016 and includes the recommended administration technique in TKA based on existing evidence and surgeon experience [8]. It also describes the standardized presurgical, intrasurgical, and postsurgical multimodal analgesia regimen, as well as the validated patient-reported outcome measures used, including the visual analog scale (VAS) for pain at 0,4,6,8, 10, 12, 24, 28, 32, 36, 48, 52, 56, 60, and 72 hours, the overall benefit of analgesia score measured every 24 hours, and the timed up and go test and 6-minute walk test, both measured twice daily starting on the day of surgery. The repeated VAS measurements were required to calculate area under the curve, which more fully captures the time spent at different levels of pain severity compared with less frequent measurements.In contrast, it is unclear how often the VAS was used to measure pain in the study by DeClaire et al, how the ...