The purpose of this prospective study is to examine the effect of two local anesthetics used in adductor canal blocks, with relation to pain, analgesic consumption, mobility, and pain related interference with activities and hospital length of stay. The two agents are bupivacaine and ropivacaine. The purpose of this trial is to examine the effect of these drugs being used in adductor canal blocks for pain relief, analgesic consumption, mobility, and pain related interference with activities and hospital length of stay.

Total knee arthroplasty (TKA) is associated with intense early postoperative pain. Effective pain management following total knee arthroplasty is imperative to facilitate early ambulation, mobilization and rehabilitation. The postoperative pain regimen should enhance functional recovery in addition to providing efficient analgesia with minimal side effects. To manage postoperative pain effectively, multimodal analgesia including acetaminophen, Toradol, Solu-Medrol, opioids and local anesthetics are used. Periarticular infiltration performed intra-operatively combined with ultrasound guided adductor-canal peripheral nerve blocks are effective in reducing pain following a TKA without causing quadriceps motor block which can impede mobilization. There are no published trials that the investigators could find to date, comparing adductor canal block with a single dose Exparel and adductor canal block with standard ropivacaine.

A liposome is a manufactured spherical lipid vesicle that can be used to slowly release a drug thereby extending its duration of action. Exparel is such a compound that slowly releases bupivacaine. Local anesthetics block the conduction of all excitable tissue in a dose related fashion. The first tissues that are affected are nerves, which make these drugs of choice in neural block. Their local adverse effects include neurovascular manifestations are prolonged numbness, tingling, feeling of "pins and needles" or strange sensations. These effects are reversed with time. There are no additional potential risks or adverse effects due to the procedures or drugs being administered. The procedure is well established and the local anesthetics have a history of long term use in humans.

Inclusion Criteria:

• Age 18 and up undergoing a total knee replacement with single surgeon. American Society of Anesthesiologists Physical Status Classification Scale (ASA) 1-3.

Exclusion Criteria:

• Allergy to local anesthestic, pre-existing peripheral neuropathy, revision surgery