This is a retrospective study looking at patients who received a nerve block for surgery and assessing pain after the nerve block resolves, with or without an educational intervention, over two periods of time.

Regional anesthesia (RA) is a vital tool that can serve as the primary anesthetic or as part of a multimodal perioperative pain regimen. RA is strongly associated with decreased acute and persistent pain and opioid consumption postoperatively. However, some patients experience an acute worsening of pain into the severe range around the time of RA resolution, also known as "rebound pain" (RP). The incidence of RP has been reported as high as 40-50% after a single shot nerve block for patients undergoing ambulatory surgery.

This retrospective study aims to look at patients who received a nerve block for surgery and assessing pain after the nerve block resolves in the presence and absence of certain interventions, such as a multidisciplinary educational intervention.

The investigators will assess patients who received a primary total knee arthroplasty who received a single shot adductor canal nerve block, received pericapsular injection by the surgeon, and had a length of stay > 16 hours.

Inclusion Criteria:

• primary total knee arthroplasty
• received an adductor canal nerve block
• received pericapsular injection by surgeon intraoperatively
• admitted for overnight stay and > 16 hours post-nerve block

Exclusion Criteria:

• age < 18
• prior total knee arthroplasty on ipsilateral knee

Using the Mass General Brigham Enterprise Data Warehouse, electronic health record data will be retrieved: adult patients, 18 years of age or older, who received a primary total knee arthroplasty, an adductor canal nerve block, pericapsular injection, and admitted to stay overnight (>16 hours post nerve block).