The primary objective of this study is to examine the change from pre-operative baseline to two year postoperative functional performance improvement for the ATTUNE primary, cementless TKA RP system as measured with the KOOS questionnaire (KOOS-ADL sub-score). This will be carried out for two configurations: cruciate retaining rotating platform (ATTUNE Cementless CR RP) and posterior stabilized rotating platform (ATTUNE Cementless PS RP).

The secondary objectives of this study are:

• Evaluate change from preoperative baseline in post-operative outcomes using additional patient reported measures at 2 years: PKIP (overall and sub-scores), KOOS (overall and sub-scores), AKS and EQ-5D-3L.
• Evaluate change from preoperative baseline in pain and satisfaction over time as measured using a modified VAS Pain Score (discrete numbers rather than a continual scale) at 2yr.
• Evaluate type and frequency of Adverse Events
• Evaluate survivorship of the ATTUNE Primary Cementless TKA system for the CR RP and PS RP configurations using Kaplan-Meier survival analysis at 2yr and 5yrs.
• Evaluate primary, cementless ATTUNE TKA fixation through zonal radiographic analysis of the bone-implant interface at 6wk, 6mo, 1yr, and 2yr after surgery.
• Evaluate any changes in anatomic tibiofemoral, femoral component and tibial component alignment at 2 years compared to the first postoperative radiographs.

Inclusion Criteria:

• Subject is male or female and between the ages of 22 and 80 years at the time of surgery, inclusive.
• Subject was diagnosed with NIDJD.
• Subject, in the opinion of the Investigator, is a suitable candidate for cementless primary TKA using the devices described in this CIP with either resurfaced or non-resurfaced patellae.
• Subject that is willing to give voluntary, written informed consent to participate in this clinical investigation and authorize the transfer of his/her information to the Sponsor
• Subject is currently not bedridden
• Subject, in the opinion of the Investigator, is able to understand this clinical investigation and is willing and able to perform all study procedures and follow-up visits and co-operate with investigational procedures.
• Subject is able to read, and comprehend the Informed Consent Document as well as complete the required PROs in either English or one of the available translations.

Exclusion Criteria:

• The Subject is a woman who is pregnant or lactating.
• Contralateral knee has already been enrolled in this study .
• Subject had a contralateral amputation.
• Previous partial knee replacement (unicompartmental, bicompartmental or patellofemoral joint replacement), patellectomy, high tibial osteotomy or primary TKA in affected knee.
• Subject is currently diagnosed with radicular pain from the spine that radiates into the limb to receive TKA.
• Subject has participated in a clinical investigation with an investigational product (drug or device) in the last three (3) months.
• Subject is currently involved in any personal injury litigation, medical-legal or worker's compensation claims.
• Subject, in the opinion of the Investigator, is a drug or alcohol abuser (in the last 5 years) or has a psychological disorder that could affect their ability to complete patient reported questionnaires or be compliant with follow-up requirements.
• Subject was diagnosed and is taking prescription medications to treat a muscular disorder that limits mobility due to severe stiffness and pain such as fibromyalgia or polymyalgia.
• Subject has a significant neurological or musculoskeletal disorder(s) or disease that may adversely affect gait or weight bearing (e.g., muscular dystrophy, multiple sclerosis, Charcot disease).
• Subject is suffering from inflammatory arthritis (e.g., rheumatoid arthritis, juvenile rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, etc.).
• Subject has a medical condition with less than five (5) years life expectancy.
• Uncontrolled gout

An independent radiographic reviewer will be assessing all radiographs from the study.