This is a retrospective/prospective, open-label single cohort, multicenter study to collect relevant clinical data from 147 subjects with unicompartmental degeneration of the knee in whom the Journey UNI UKS was previously implanted.

The purpose of the current investigation is to assess the safety and effectiveness of the JOURNEY UNI Unicompartmental Knee System (UKS) in patients with non-inflammatory degenerative joint disease (NIDJD) of the knee who previously had the Journey UNI UKS implanted. This clinical study will prospectively evaluate the 36 and 60-month safety and performance of the JOURNEY UNI UKS in patients with NIDJD of the knee who required lateral or medial knee compartment replacement.

Inclusion Criteria:

1. Between 12 and 48 months previously, subject had unicompartmental knee replacement implanted for unicompartmental, NIDJD including OA, traumatic arthritis, avascular necrosis, for correction of functional deformity, or to repair a fracture that was unmanageable using other techniques.
2. Subject received a Journey UKS implant (consisting of a femoral component, tibial baseplate, and a tibial insert).
3. Subject was considered skeletally mature at the time of surgery and was at least 18 years of age.
4. Subject is willing to have retrospective data collected and to participate in required prospective follow-up visit(s) at the investigational site and to complete study procedures and questionnaires.
5. Subject has consented to participate in the study by signing the Institutional Review Board (IRB)/Ethics Committee (EC)-approved informed consent form (ICF).

Exclusion Criteria:

1. Subject has Body Mass Index (BMI) > 40 within 1 month of surgery.
2. Subjects who have received the Journey UNI UKS as part of a revision surgery.
3. Subject has a condition that may interfere with the unicompartmental knee arthroplasty (UKA) survival or outcome (e.g. Paget's or Charcot's disease, vascular insufficiency, muscular atrophy, uncontrolled diabetes, moderate to severe renal insufficiency or neuromuscular disease).
4. Subject has a known allergy to study device or one or more of its components.
5. Subject, in the opinion of the Principal Investigator (PI), has an emotional or neurological condition that would preempt his/her ability or willingness to participate in the study including mental illness, mental retardation, drug or alcohol abuse.
6. Subject is entered in another investigational drug, biologic, or device study or has been treated with an investigational product in the past 30 days.
7. Subject is known to be at risk for loss to follow-up, or failure to return for scheduled visits.

Investigators will pre-screen all subjects that have previously undergone UKA using the Journey UNI UKS system between 12 and 48 months previously using only the existing information in the medical records.