Postmarketing Study to Determine Performance of the SIGMA HP® PARTIAL KNEE SYSTEM

This is a postmarketing study to assess the overall performance and survivorship of the SIGMA HP® PARTIAL KNEE SYSTEM.

The purpose of this study is to collect more information about the Sigma HP® Partial Knee System made by DePuy International. The aim of this study is to measure how this particular type of knee replacement performs over a two year period.

Eligibility Criteria:
Inclusion Criteria:

* Male or female subjects, aged at least 21 years.
* Subjects who are able to give voluntary, written informed consent to participate in this clinical investigation and from whom consent has been obtained.
* Subjects, who, in the opinion of the Clinical Investigator, are able to understand this clinical investigation, co-operate with the investigational procedures and are willing to return to the hospital for all the required post-operative follow-ups.
* Subject has non-inflammatory degenerative joint disease (NIDJD), including: osteoarthritis, posttraumatic arthritis, avascular necrosis and chondrocalcinosis.
* Subject has a functional stable knee.
* Subject, in the opinion of the Investigator, is suitable for either a single or bicompartmental knee replacement.
* Subject meets the following selected radiographic parameters:

  * X-ray evaluation confirms the presence of NIDJD
  * Disease location: 1 to 2 compartments, maximum. Disease can be present in the patellofemoral compartment, the medial tibiofemoral compartment, lateral tibiofemoral compartments alone or in any two compartments.
  * Disease severity: Kellgren and Lawrence44 Grade II or greater for all compartments replaced.

Exclusion Criteria:

* Subjects who, in the opinion of the Clinical Investigator, have an existing condition that would compromise their participation and follow-up in this clinical investigation.
* Women who are pregnant.
* Subjects who are known drug or alcohol abusers or with psychological disorders that could affect follow-up care or treatment outcomes.
* Subjects who have participated in a clinical investigation with an investigational product in the last 3 months.
* Subjects who are currently involved in any injury litigation claims.
* Multiple joint involvement that will compromise rehabilitation (for example: advanced hip, ankle or spine disease).
* Known to be a prisoner, mentally incompetent, an alcohol / drug abuser, involved in medical-legal case or worker's compensation
* Previous knee arthroplasty (any type) in any one of the three compartments of the knee.
* Requires more than a lateral soft tissue release or an anterior cruciate ligament reconstruction.
* Uncorrectable anatomical tibio-femoral angle.
* Bone deficiency requiring structural bone grafts to support the implants.
* Previous patellectomy.
* For Subjects indicated for a patellofemoral arthroplasty, Subject has uncorrected patella baja (Caton-Deschamps ratio less than or equal to 0.6).
* Tri-compartmental disease process (patella-femoral, medial tibio-femoral and lateral tibio-femoral).
* Active bacterial infection that may spread to other areas of the body (e.g., osteomyelitis, pyogenic infection of knee joint, urinary tract infection, etc.).
* Significant neurological or musculoskeletal deformity or a disease that may affect gait or weight bearing, (e.g., muscular dystrophy, multiple sclerosis, amputation).
* Known allergy to implant materials.