Inclusion Criteria - 200 patients undergoing primary THA/TKA for osteoarthritis:

• Adult (18 years old or greater).
• Primary diagnosis is osteoarthritis (OA).
• Must be primary total joint arthroplast  .

Inclusion Criteria - 200 patients undergoing revision THA/TKA for infection with culture positive Staphylococcus aureus:

• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-UHMWPE bearing surface.
• At least 2 positive intraoperative cultures depicting Staphylococcus aureus.
• Have clinical picture consistent with infection, including, but not limited to:
  • Patient symptomatic;
  • Increased laboratory values (WBC, ESR, CRP);
  • Positive aspiration;
  • Necessitates revision surgery in the opinion of the consulting surgeon.

Inclusion Criteria - 200 patients undergoing revision THA/TKA for infection with culture positive Staphylococcus epidermidis:

• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-UHMWPE bearing surface.
• At least 2 positive intraoperative cultures depicting Staphylococcus epidermis.
• Have clinical picture consistent with infection, including, but not limited to:
  • Patient symptomatic;
  • Increased laboratory values (WBC, ESR, CRP);
  • Positive aspiration;
  • Necessitates revision surgery in the opinion of the consulting surgeon.Inc

Inclusion Criteria - 200 patients undergoing revision THA/TKA for culture negative infection:

• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-UHMWPE bearing surface.
• Negative cultures at time of surgery, but has one of following:
  • Sinus tract (as determined by consulting surgeon);
  • Gross purulence (as determined by consulting surgeon);
  • Acute inflammation (as determined by consulting pathologist);
  • Symptomatic patient with elevated inflammatory markers (WBC, CRP, ESR);
  • Necessitates revision surgery in the opinion of the consulting surgeon.

Inclusion Criteria - 200 patients undergoing revision THA/TKA for culture negative osteolysis:

• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-UHMWPE bearing surface.
• Evidence of osteolysis on either serial plain radiographs (AP / cross-table lateral) or advanced imaging (CT or MRI with artifact minimization).
• Occurs in the absence of infection:
  • Patient asymptomatic;
  • Normal laboratory values (WBC, ESR, CRP);
  • Negative aspiration;
  • Negative cultures at time of surgery;
  • Necessitates revision surgery in the opinion of the consulting surgeon.
• 100 patients undergoing revision THA for metal reaction.
• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-metal bearing surface.
• Soft tissue mass noted on MRI or US.
• Periprosthetic pathologic tissue reveals chronic inflammation with perivascular lymphocytic aggregates.
• Occurs in absence of infection:     
  • Patient asymptomatic;
  • Normal laboratory values (WBC, ESR, CRP);
  • Negative aspiration;
  • Negative cultures at time of surgery;
  • Necessitates revision surgery in the opinion of the consulting surgeon.

Inclusion Criteria - 100 patients undergoing revision TKA for flexion instability:

• Adult (18 years old or greater).
• Index surgical procedure was for OA .
• Patient must have metal-on-UHMWPE bearing surface.
• Evidence of instability on either serial plain radiographs (AP / cross-table lateral) or advanced imaging (CT or MRI with artifact minimization).
• Occurs in the absence of infection:
  • Patient asymptomatic;
  • Normal laboratory values (WBC, ESR, CRP);
  • Negative aspiration;
  • Negative cultures at time of surgery;
  • Necessitates revision surgery in the opinion of the consulting surgeon.

Inclusion Criteria - 100 patients undergoing revision TKA for arthrofibrosis:

• Adult (18 years old or greater).
• Index surgical procedure was for OA.
• Patients must have metal-on-PE bearing surface.
• Evidence of arthrofibrosis on clinical exam and/or plain radiographs.
• Occurs in the absence of infection:
  • Patient asymptomatic;
• Normal laboratory values (WBC, ESR, CRP);
• Negative aspiration;
• Negative cultures at time of surgery;
• Necessitates revision surgery in the opinion of the consulting surgeon.

Exclusion Criteria - 200 patients undergoing primary THA/TKA for osteoarthritis:

• Revision surgery.
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 200 patients undergoing revision THA/TKA for infection with culture positive Staphylococcus aureus:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.).
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 200 patients undergoing revision THA/TKA for infection with culture positive Staphylococcus epidermidis:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.) .
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 200 patients undergoing revision THA/TKA for culture negative infection:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.) 
• History of malignancy in operative extremity
• Steroid use after index surgical procedure
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 200 patients undergoing revision THA/TKA for culture negative osteolysis:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.) .
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 100 patients undergoing revision THA for metal reaction:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.) .
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 100 patient undergoing revision TKA for instability:

• Any diagnosis other than osteoarthritis as reason for index surgical procedure (i.e., inflammatory arthritis, posttraumatic arthritis, septic arthritis, osteonecrosis, etc.).
• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.

Exclusion Criteria - 100 patients undergoing revision TKA for arthrofibrosis:

• History of malignancy in operative extremity.
• Steroid use after index surgical procedure.
• Presence of a condition interfering with the ability to provide informed consent.