The aim of this study is to determine if vitamin D supplementation is associated with differences in short-term recovery in patients following total knee arthroplasty compared to patients who do not receive supplementation. If so, vitamin D supplementation has the potential to become widely incorporated into the routine care for patients undergoing knee replacements.

Patients will be enrolled from the clinics of Dr. Denis Nam and Dr. Craig Della Valle, two fellowship-trained orthopedic surgeons in the division of Adult Reconstruction at Midwest Orthopedics at Rush University Medical Center. Study staff will screen the clinic schedule of each surgeon and will discuss the purposes of the investigation at the time of their visit. If the patient is willing to participate in the investigation, verbal and written consent will be obtained by the study staff. At the time of consenting, patients will also be asked to perform a TUG test and will be asked to complete the questions that comprise the functional component of the KSS score.

This study will be tripled-blinded, thus, the patients, clinicians, and research staff involved will be unaware of patient allocation during this study. Each patient will receive a study ID, and a computer randomization system will be used to allocate patients to receive either vitamin D3 or placebo based on their study ID. Only members of the Rush pharmacy staff will possess the list matching the study ID to the study group assignment, ensuring that the study remains triple-blinded and that study coordinators are unaware of a patient's assignment when he or she picks up the study medication from the pharmacy.

Patients randomized to the experimental arm of the study will receive 50,000IU of vitamin D3 following surgery and asked to take the medication orally following surgery. Vitamin D3 was selected over vitamin D2 as the former is less expensive and is more effective at raising serum 25-OH vitamin D levels than the latter. The regimen of 50,000IU given once was selected as this regimen has been previously used without side effects in previous studies and has been shown to be as effective as other regimens that utilize more frequent dosing with smaller doses. Patients randomized to the control arm will receive placebo tablets and advised to consume their medication similar to the treatment arm. Both groups of patients will receive their medications from the pharmacy at Rush Medical Center, which will be responsible for providing patients with the appropriate regimen. All patients will receive the same postoperative multimodal analgesic regimen that is normally administered to patients undergoing THA and TKA at Rush University Medical Center.

In accordance with current standard post-operative care, patients will be asked to follow-up with their surgeon in clinic at 3 weeks and 6 weeks following surgery. At these post-operative visits, patients will be asked to repeat the TUG test and the 17-questions of the functional component of the KSS score.

Inclusion Criteria:

• Any patient undergoing primary total knee arthroplasty for osteoarthritis
• Age ≥ 18 years old
• Willingness to undergo randomization and return for all scheduled visits

Exclusion Criteria:

• Age > 80 years old
• American Society of Anesthesiologists (ASA) Score ≥ 4
• Other supplemental vitamin D or Calcium use including their analogs: ergocalciferol, calcitriol, dihydrotachysterol, and paricalcitol
• Current cancer
• Malabsorption syndromes
• Inability to take medications orally
• Renal impairment defined as a glomerular filtration rate (GFR) < 30 mL/minute or creatinine >1.3 mg/dL
• History of hypercalcemia defined as albumin-corrected hypercalcemia >12 mg/dL

Adverse events occurring 3 months post operative

The dosing regimen included a one-time dose of 50,000IU vitamin D3, which may not be large enough to identify clinically significant differences. A higher than anticipated drop-out rate in this study occurred. Additionally, patients already taking vitamin D supplements were excluded from participation. We did not test patients for vitamin D deficiency preoperatively. We were unable to conduct a cost-analysis to support the cost-effectiveness of nonselective treatment.