The purpose of this study is to determine implant design and determine if method of fixation cemented versus cementless results in different bone loss patterns. The investigators also want to determine if clinical outcomes correlate with bone density changes.

Patients who present to the clinical practices of Dr. Ryan Nunley and Dr. Robert Barrack and are suitable candidates for primary total knee arthroplasty(TKA) type assigned either cemented or cementless and Triathlon knee or Depuy by surgeon will be screened for eligibility and invited to participate. Data collected for the study will include standard of care clinical and radiographic evaluations collected during office visits and surgery, Dual Energy X-Ray Absorptiometry(DEXA) Bone density monitoring, as well as study-specific patient questionnaires. Clinical, radiographic and questionnaire data will be collected pre-operatively, at the time of surgery, and at 6 weeks, 1 year and beyond, and 2 years and beyond post-operatively. Patients will complete the following outcomes questionnaires preoperatively: New Knee Society Score, Oxford Knee Score, UCLA Activity Score, SF-12, and EQ-5D. The following questionnaires will be collected at four to six weeks, six months, one year and beyond, and two years and beyond postoperatively: New Knee Society Score, Forgotten Joint Score, Washington University Knee Satisfaction and Function Questionnaire, Oxford Knee Score, UCLA Activity Score, SF-12, and EQ-5D, and a Pain Drawing.

Inclusion Criteria:

• Patients who qualify for a Primary Total knee using Triathlon Implant(thin tray) or Depuy Attune(thick tray) Implant
• 18-75 years of age
• Willing to sign informed consent
• Willing to return for all follow-up visits

Exclusion Criteria:

• Patients with inflammatory arthritis
• BMI > 40
• Patient with an active infection or suspected infection in the joint
• Patient who have undergone osteotomy
• Patients who have a previous diagnosis of osteopenia/osteoporosis or patients with weak bones and/or currently on medications to increase bone density/who have poor bone quality
• Patients who have had previous patella fracture or surgery
• Patients who have had previous knee or hip replacement surgery on the ipsilateral side
• Patients who require patellar resurfacing
• Patient with major medical/muscular/orthopedic deformities
• Unable to undergo DEXA scanning.
• Female patients of childbearing potential and an interest in getting pregnant in the future *NOTE: Patients receiving simultaneous bilateral total knee arthroplasties are eligible. Both knees are eligible for enrollment as long as all other inclusion/exclusion criteria are met for each knee. If only one knee is eligible it will be included. Patients receiving staged bilaterals are also eligible, provided that each knee meets the inclusion exclusion criteria.

A. Patients who qualify for a Primary Total Knee Arthroplasty using Stryker Triathlon Implant(thin tray) or Depuy Attune(thick tray) Implant