A Prospective Multicenter Longitudinal Cohort Study of the Mymobility Platform

Inclusion Criteria 1. Subject must be 18 years of age or older. 2. Subject qualifies for a primary, unilateral total or partial knee arthroplasty, based on physical exam and medical history. 3. Investigator plans to treat subject with a commercially-available device, used on-label according to the manufacturer's instructions for use, as part of their clinical care. 4. Subject owns and maintains an iPhone capable of pairing to the Apple Watch, supporting iOS updates and is compatible with the mymobility App. 5. Subject is willing and able to complete the protocol required follow-up. 6. Subject is able to read and understand the language used in the mymobility App for their region. 7. Subject is willing and able to provide written Informed Consent and Authorization by signing and dating the IRB/EC approved Informed Consent Form and Authorization. Where applicable, subject must also be willing to provide authorization for use of protected health information in accordance with local privacy laws. 8. Subject is mobile with no more than a single cane/single crutch assist preoperatively. Exclusion Criteria 1. Subject is a current alcohol or drug abuser as defined by the investigator. 2. Subject is considered a member of a protected population (e.g., prisoner, mentally incompetent, etc.). 3. Subject has systemic inflammatory arthropathies which would interfere or compromise the activity profiles within this study. 4. Subject is currently participating in any other surgical intervention, physical therapy or pain management study which would compromise the results of this study. 5. Subject requires simultaneous or staged bilateral replacements, staged\<90 days apart. Subjects can be enrolled into the study for the second, staged arthroplasty if scheduled \>89 days after their first, contralateral replacement.