Enrollment and data collection insufficient to continue study.

The purpose of this study is to evaluate the use and efficacy of the Encore Foundation Knee System in a group of 200 patients for whom data has already been collected.

Inclusion Criteria:

• Have knee joint disease related to one or more of the following

  • osteoarthritis
  • post-traumatic arthritis
  • inflammatory tissue disorders
  • arthritis secondary to other diseases
  • Avascular necrosis of the femoral condyles;

• Skeletal maturity

• Less than 70 on the Knee Society Score (rating score)

• Sufficient bone stock, as judged by radiographs, to support primary knee implant

• Sufficient collateral ligaments to support the device, as judged by physician during stability testing (varus/valgus and flexion/extension) and less than 45 degree varus/valgus deformity and/or 90 degree flexion contracture

• Patient is likely to be available for evaluation for the duration of the study

• Able and willing to sign the informed consent and follow study procedures

• Patient is not pregnant

• No infection present

• No known materials sensitivity

Exclusion Criteria:

• Skeletal immaturity
• Greater than or equal to 70 on preoperative Knee Society Score (Rating Score)
• Post-patellectomy
• Insufficient bone quality which may affect implant stability
• Insufficient collateral ligaments, as judged by the physician. Greater than 45 degree varus/valgus deformity and/or 90 degree flexion contracture.
• Neurological conditions that might hinder patient's ability to follow study procedures (i.e., any that restrict physical activities such as Parkinson's Disease, Multiple Sclerosis, previous stroke which affects lower extremity)
• Mental conditions that may interfere with ability to give an informed consent or willingness to fulfill the study requirements (i.e., severe mental retardation such that the patient cannot understand the informed consent process, global dementia, prior strokes that interfere with the patient's cognitive abilities, senile dementia, and Alzheimer's Disease)
• Prisoners
• Conditions that place excessive demand on the implant (i.e. Charcot's joints, muscle deficiencies, refusal to modify postoperative physical activities, skeletal immaturity)
• Patient is pregnant
• Infection present
• Materials sensitivity

Individuals who meet the indications for use of the Foundation Knee device AND who meet the inclusion/exclusion criteria