Pain control after knee replacement requires analgesia to both the top (anterior) and bottom (posterior) portion of the the knee. Presently we use a nerve block for the anterior portion. The investigators want to to examine if giving Exparel into the posterior portion will give better pain relief.

Hypothesis: There is no difference in, the use of analgesics or the length and quality of analgesia and no decrease in the time to be able to accomplish simple to complex knee movements using Exparel infiltration when compared to controls.

Objectives:

1. Is to assess the efficacy of pain control of Exparel vs. controls when injected into the posterior capsular space after total knee arthroplasty
2. Asses the opioid use after Exparel vs. controls
3. Asses the time to simple and complex knee movement and ambulation.
4. The safety of Exparel will be assessed by the occurrence of all postsurgical adverse events and serious adverse events through Day 30.

Methods:

After institutional review board (IRB) approval, 20 subjects will be consented to participate in the study. The study includes subjects undergoing total knee arthroplasty either under general or spinal anesthesia. This study will include men and women (18 - 75 years) who have American Society of Anesthesiologist physical classification status 1 - 3 and underwent total knee arthroplasty.

Subjects will be divided into two groups, Group A (control) to receive 20ml of saline while Group B (study) to receive 20ml of liposomal bupivacaine into the posterior capsular space during total knee arthroplasty. Patients from both groups will receive a femoral nerve block with catheter placement for continuous infusion of local anesthetic. All subjects will have access to rescue analgesics after surgery. Multimodal analgesia will supplement pain as per standard care by the anesthesia team. Tylenol Orally 1g three times daily (not to exceed 4g in 24hrs), oxycontin 10mg orally, twice/day, Celebrex 200 mg orally once a day and Percocet 5/325 prn will serve as this multimodal approach. The time, day and number of requests for break through (additional) analgesia will be noted by both anesthesia team and primary care team. Pain scores will be assessed using a 0 - 10 numeric scale. Pain will be assessed for the following intervals: hospital arrival, post anesthesia care unit (PACU) arrival, 2, 4, 8, 12, 24, 48, 72, hours later and after hospital discharge 10 +/- 5 days after the block. Pain inquiries will assess both posterior and anterior aspects of the knee. Pain at rest and for simple leg movements (knee extension, straight leg raise) to fully ambulatory will be noted. These assessments will be made in conjunction with rehabilitation and physical therapy specialists.

Inclusion Criteria:

• Patients aged 18-75 years inclusive and American Society of Anesthesiologist physical status 1-3
• Patients undergoing knee replacement (total knee arthroplasty)
• Subjects must be physically and mentally able to participate in the study and complete all study assessments.
• Subjects must be able to give fully informed consent to participate in this study after demonstrating a good understanding of the risks and benefits of the proposed components of infiltration into the posterior capsule of the knee.

Exclusion Criteria:

• History of hypersensitivity or idiosyncratic reactions to amide-type local anesthetics
• Any subject whose anatomy, or surgical procedure, in the opinion of the Investigator, might preclude the potential successful performance of a appropriate Exparel infiltration into the posterior capsule of the knee.
• Any subject who in the opinion of the Investigator, might be harmed or be a poor candidate for participation in the study.
• Any subject, who in the opinion of the Investigator, is on chronic pain medicine (opioids), including large doses of non-steroidal anti-inflammatory drugs s.
• Subjects who have received any investigational drug within 30 days prior to study drug administration, or planned administration of another investigational product or procedure during their participation in this study.
• History of pre-existing neurological disorders/neuropathy
• Morbid Obesity

72 hours post-operative