It is essential that serum 25(OH)D changes following surgery be clarified, and the mechanism(s) underpinning these changes be identified. As such, the overarching hypothesis of this study is that elective total hip arthroplasty reduces serum total 25(OH)D.

Inclusion Criteria:

• Elective total hip arthroplasty for osteoarthritis
• Age 50+
• Able and willing to sign informed consent
• English speaking
• Willing to not alter vitamin D supplementation use for the duration of this study
• Willing to utilize sunscreen of SPF-15 or higher when sun exposure for more than 15 minutes is expected

Exclusion Criteria:

• Illnesses known to affect inflammatory marker status including, but not limited to, rheumatoid arthritis, systemic lupus erythematosis and mixed connective tissue disease
• Chronic diseases that could potentially affect DBP status, e.g., chronic kidney disease stage requiring dialysis, nephrotic syndrome and chronic hepatitis,
• Hip arthritis from causes other than osteoarthritis
• Treatment with medications with potential to affect vitamin D metabolism, (e.g., phenytoin, phenobarbital, teriparatide or active vitamin D analogues) or to potentially interfere with 25(OH)D measurement by HPLC (atavaquone) within the preceding three months.
• Treatment with high dose vitamin D supplementation (50,000 IU weekly or more frequently) within the preceding three months. Note; subjects on a stable daily vitamin D dose will be allowed to participate
• Surgical procedure within the preceding six months
• Use of tanning beds or salons or unwillingness to utilize sunscreen during periods of sun exposure of 15 minutes or longer

Adults age 50+ undergoing elective total hip arthroplasty for osteoarthritis will be included. We will exclude individuals having these procedures for other conditions, e.g., rheumatoid arthritis, avascular necrosis and those undergoing reoperation of a previous hip arthroplasty.