The purpose of this research is to collect data on patients that had the Legion Porous HA Tibial Baseplates and/or the Legion Porous HA Femoral component implanted in the past. Smith & Nephew will evaluate the safety and performance of these implants for 10 years post-surgery.

Inclusion Criteria:

1. Subject received primary TKA with the LEGION Porous HA Tibial Baseplates (either with holes or without holes) and/or the LEGION Porous HA CR Femoral Component, due to degenerative joint disease (primary diagnosis of osteoarthritis, post-traumatic arthritis, or degenerative arthritis).

2. Subject received primary TKA between 24 and 60 months prior to the time of consent.

   Inclusion criteria for prospective follow-up (subjects must meet criteria 1 & 2 from above and criteria 3,4 and 5 below):

3. Subject agrees to consent and to follow the prospective study visit schedule (as defined in the study protocol and informed consent form) by signing the IRB/IEC approved informed consent form.

4. Subject must be available through ten (10) years postoperative follow-up.

5. Subject is able to read, understand, and communicate responses to Patient Reported Outcome assessments in English.

Exclusion Criteria:

Exclusion criteria for retrospective chart review - Any one (1) of the following criteria will disqualify a potential subject from participation in the retrospective chart review:

1. Subject received TKA on the contralateral knee as a revision for a previously failed total or unicondylar knee arthroplasty

2. Subject has ipsilateral hip arthritis resulting in flexion contracture.

3. At the time of enrollment, subject has one or more of the following arthroplasties that are not fully healed and well-functioning, as determined by the investigator: Ipsilateral or contralateral primary total hip arthroplasty or hip resurfacing arthroplasty; Contralateral primary total knee or unicondylar knee arthroplasty.

4. Subject has a condition that may interfere with the TKA survival or outcome (e.g. Paget's or Charcot's disease, vascular insufficiency, lupus, muscular atrophy, uncontrolled diabetes, moderate to severe renal insufficiency or neuromuscular disease).

5. Subject has a known allergy to one or more of its components of the study device.

6. Subject is entered in another drug, biologic, or device study or has been treated with an investigational product in the past 30 days.

   Exclusion criteria for prospective follow-up - Any one (1) of the criteria from 1-6 above will disqualify a potential subject from participation in the prospective follow-up) as will any one (1) of the below criteria 7, 8 and 9:

7. Subject, in the opinion of the Principal Investigator (PI), has an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study including mental illness, mental retardation, drug or alcohol abuse.

8. Subject is known to be at risk for loss to follow-up, or failure to return for scheduled visits.

9. Subject is found to have had a revision of the study device(s).

Maximum of 150 subjects enrolled to obtain a minimum of 150 implanted components:

• Maximum of 75 subjects to obtain a minimum of 75 implanted tibial baseplate components (with or without holes) to attain 30 evaluable baseplates with holes and 30 evaluable baseplates without holes (i.e. a combined total of 60 evaluable implanted baseplate components)
• Maximum of 75 subjects to obtain a minimum of 75 implanted LEGION Porous HA CR Femoral Components to attain 60 evaluable components.

Note: Some subjects may have received both the LEGION Porous HA Tibial Baseplate (with or without holes) and the LEGION Porous HA CR Femoral Component during their TKA procedure.