Effective pain management following total knee arthroplasty is important to facilitate early mobilization and rehabilitation. To manage post-operative pain, multimodal analgesia, including acetaminophen, NSAID's, gabapentin, opioids and local anesthetics are used. However, local anesthetics injected into the femoral nerve area may cause a block in motor function of the quadriceps muscle. Both adductor-canal peripheral nerve block performed pre-operatively, and periarticular infiltration performed intra-operatively are effective in reducing pain following TKA without causing quadriceps motor block which can impede mobilization. No published trials have been found that compare single shot adductor-canal block plus periarticular infiltration to periarticular infiltration only or adductor-canal nerve block only. The purpose of this trial is to examine the effect of 3 different approaches to nerve blockade: 1) adductor-canal block plus periarticular infiltration; 2) adductor-canal block only; 3) periarticular infiltration only, on pain, analgesic consumption, mobility, pain related interference with activities and length of hospital stay in participants undergoing unilateral TKA. Patients will be eligible for participation if they are 18 years old or older, and can speak, and read English. Ninety-six trial participants will be randomized to receive 1 of the 3 approaches to nerve blockade as part of their pain management plan. Outcomes will be measured on post-operative days 1 and 2 and length of stay will be calculated in hours after the participant is discharged to home. It is hypothesized that participants that receive both adductor-canal nerve block plus periarticular infiltration will report less pain, improved mobility and less pain related interference with activities.

Hypothesis:

The combination of adductor-canal peripheral nerve block with periarticular intra-operative infiltration (AC+PI) provides superior analgesia and preserves motor function as compared to adductor-canal block (AC) only or periarticular infusion (PI) only.

Specific Aims:

The primary outcome of this trial is to examine pain on walking, using a 0 to 10 numeric rating scale (NRS), at post-operative day 1 in patients who undergo TKA using 3 different approaches to nerve blockade: 1) adductor-canal block plus periarticular infiltration; 2) adductor-canal block only; 3) periarticular infiltration only.

The secondary outcomes of this trial are to examine, in patients who undergo TKA using 3 different approaches to nerve blockade: 1) adductor-canal block plus periarticular infiltration; 2) adductor-canal block only; 3) periarticular infiltration only:

1. pain at rest on post-operative day 1 and day 2 at 1000
2. pain with walking on post-operative day 2
3. pain with knee flexion on post-operative day 1 and day 2 at 1000
4. analgesic consumption on post-operative day 1 and day 2
5. distance walked on post-operative day 1 and day 2
6. pain related interference with activities on post-operative day 1 and day 2
7. length of stay

Inclusion Criteria:

• age 18 years or older
• ASA I-III
• eligible for spinal anesthetic
• able to speak
• read and understand English
• willing to participate in the trial
• will be discharged home.

Exclusion Criteria:

• contraindication to regional anesthesia
• have an allergy to local anesthetics
• contradiction to NSAID's
• have chronic pain that is not related to their knee joint
• have been using opioids on a chronic basis (3 months or longer)
• have a pre-existing peripheral neuropathy involving the operative site.