MicroPort Orthopedics (MPO) is conducting this study to build upon the results of a previous study which showed the Medial Pivot (MP) system required lower quadriceps activation than subjects implanted with a Posterior stabilized (PS) system preforming the same activities of daily living.

MicroPort Orthopedics (MPO) is conducting this study to build upon the results of a previous study which showed the Medial Pivot (MP) system required lower quadriceps activation than subjects implanted with a Posterior stabilized (PS) system preforming the same activities of daily living. The propose of the current study is to determine the impact of Total Knee Arthroplasty (TKA) design on muscle activation following TKA surgery.

Inclusion Criteria:

To be included in Groups 1 and 2, subjects must meet all of the following criteria:

Subject is a candidate for unilateral primary TKA for degenerative or traumatic osteoarthritis Subject is a candidate to be implanted with the specified combination of components for either Group 1 or 2 Subjects are at least 45 years old and less than 76 years of age at time of enrollment Subject is willing and able to complete required study visits and assessments Subject plans to be available through the 1 year postoperative follow-up visit Subject is willing to sign the approved Informed Consent document

To be included in Group 3, subjects must meet all of the following criteria:

Subjects are at least 45 years old and less than 76 years of age at time of enrollment Subject is willing and able to complete required study visit and assessments Subject is willing to sign the approved Informed Consent document

Exclusion Criteria:

Subjects will be excluded if they meet any of the following criteria:

Subject has both a body mass index (BMI) and waist circumference measurements greater than 35.0 kg/m2 and 102.0 cm respectively for men and 35.0 kg/m2 and 88.0 cm respectively for women at screening.

Groups 1 & 2 Only: Subject has degenerative conditions (other than osteoarthritis in the enrolled TKA) impacting joints of the lower extremities, previous joint replacement of the enrolled knee or other lower limb joint replacement, or any other past or present condition, which in the opinion of the Investigator may impact gait. Group 3 Only: Subject has degenerative condition impacting joints of the lower extremities, any previous joint replacement in the knees, or any other past or present condition, which in the opinion of the Investigator may impact gait.

Groups 1 and 2 Only: Subjects with a Kellgren-Lawrence Grading Scale of ≥2 on the contralateral knee if having severe pain or abnormal gait patterns.

Subject is currently enrolled in another clinical investigation related to lower limbs which could affect the endpoints of this protocol.

Subject is unwilling or unable to sign the Informed Consent document Subject has documented substance abuse issues Subject has an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study Subject is currently incarcerated or has impending incarceration

Study population will be selected from the orthopedic clinic at The Ottawa hospital for implanted patients. Non-implanted subjects will be selected from the community.