Total knee arthroplasty (TKA) may result in significant postoperative pain. The majority of these patients are prescribed opioids for the management of postoperative pain. Recent evidence has highlighted that postoperative opioids are being over-prescribed resulting in opioid misuse and abuse. Over-prescribing also results in a significant financial cost. This prospective observational study was designed to determine the mean amount of opioid required after TKA. This data can be used in the future as a guide to change our current practice of prescribing with the aim to reduce over-prescription.

Over prescription of opioids is currently a National epidemic . There is a call for action to address this problem urgently and anesthesiologists are well positioned to participate and lead through research to educate medical practitioners of how to prescribe the optimal dose with the ultimate goal of improved patient's safety.

Total knee arthroplasy (TKA) and total hip arthroplasty (THA) may result in significant and sustained postoperative pain. For optimal pain control, faster recovery, and better functional rehabilitation, these patients are prescribed opioids in addition to analgesic adjuncts in hospital and after discharge from the hospital. This practice stems from much evidence that demonstrated a propensity for moderate and severe pain of 52% and 16% respectively up to 30 days post discharge in patients undergoing THA and TKA.

These patients are prescribed opioids upon discharge from the hospital to control pain and to enhance optimal rehabilitation. The discharge prescription is often based on a surgeon's judgment and past experience. Furthermore, more than 50% of patients may receive suboptimal pain control resulting in pain in the early postoperative period. On the other hand, recent studies have shown that opioids are often over-prescribed. This practice not only results in a significant financial cost, but also represents a potential reservoir for opioid misuse and abuse. In Canada, the rate of dispensing high-dose opioid formulations (greater than 200mg morphine equivalents per day) increased 23.0%, from 781 units per 1000 population in 2006 to 961 units per 1000 population in 2011. Excessive opioid prescriptions can lead to excessive morbidity and mortality as evidenced in the United States where 16 917 (74%) of the 22,810 deaths relating to pharmaceutical overdose involved opioid analgesics. With respect to the financial burden, in the United States in 2007, prescription opioid abuse costs were $55.7 billion of which 45% were healthcare costs (e.g., abuse treatment).

To the author's knowledge there are no widely used objective tools or guidelines to instruct patients in self-administering opioids post-discharge or to help surgeons to avoid over or under prescribing. This may contribute to either over-dosing with opioid related side effects, or under-dosing with inadequate analgesia and rehabilitation.

In this prospective observational study we plan to determine the mean amount of opioid required post discharge after TKA that correlates with good pain management and rehabilitation outcomes. The mean amount of opioid consumed could be used in the future to guide physicians to practice proper opioid prescribing post discharge from hospital.

Inclusion Criteria:

• 18 years or older
• Having an elective total knee replacement done at Sunnybrook Holland Orthopaedic and Arthritic Centre.
• All participants must speak English and have no communication barriers.

Exclusion Criteria:

• If you are taking >10mg morphine equivalents per day
• Deemed incompetent to be able to self prescribe opioids.

All participants must be 18 years or older and are undergoing an elective total knee arthroplasty at Sunnybrook Holland Orthopaedic and Arthritic Centre. All participants must speak English and be able to receive phone calls once a week for 6 weeks after surgery.