The purpose of this research study is to evaluate the cause of thigh pain after knee replacement. Different surgical techniques will be used to help determine the cause of thigh pain, and all surgical techniques are accepted and produce good clinical results.

This research study will be a randomized study in which patients volunteer participate. "Randomized" means the patients who received the new treatment are chosen at random, similar to flipping a coin. Several factors have been identified as possible sources of thigh pain after surgery: use of a tourniquet around the thigh to control bleeding during surgery; use of an intramedullary rod during surgery or quadriceps muscle strain. Participants will be randomized into surgical groups that use/do not use a tourniquet and use/do not use intramedullary rod during surgery. A subset of participants in all surgical groups will have a MRI to look for quadriceps muscle strain.

Inclusion Criteria:

• Subjects undergoing total knee arthroplasty for osteoarthritis
• Adult patients (age 18 years or older)
• Written informed consent
• Ability to speak, read and write English or Spanish

Exclusion Criteria:

• Inability to speak, read and write English or Spanish
• Evidence of malignant disorder/neoplasm in past 60 months
• Contraindication for removal of infrapatellar fat pad
• History of smoking and not committed to give up
• Chronic skin conditions
• Connective, metabolic or skin disease
• Evidence of active infection
• Pregnancy or lactating for female subjects
• Current corticosteroid use
• Immunosuppressive medication
• Renal failure (creatine > 1.8 mg/dL)
• Hepatic failure (AST, ALT > 2x normal values; bilirubin > 2 mg/dL)
• Inflammatory joint diseases of the knee that indicate additional, conflating therapies
• Joint infection within the past 6 months
• No prisoners or mentally disabled persons
• No Workers' Compensation cases