Complex Molecular Etiology and Cellular Landscape of Hip Osteoarthritis

Inclusion Criteria for the main (OA) study: Cases: Adult patients with osteoarthritis in the hip joint and who are going through an elective total hip arthroplasty. Controls: Non-arthritis adult patients who are going through a trauma-based emergency total hip arthroplasty. \---- Inclusion Criteria for the Rheumatoid sub-study: Adult patients with rheumatoid arthritis in the hip joint and who are going through an elective total hip arthroplasty. \---- Exclusion Criteria: * The body mass index must be below 35 * Age \< 18 or \> 74 * The OA patients may not have diabetes, rheumatoid arthritis (RA), or metabolic syndrome. For the Rheumatoid sub-study, the exclusion criteria are the same as above except for the RA.