The purpose of the current investigation is to assess the safety and efficacy of a new hinged revision knee device. This device is designed to provide efficient, reproducible reconstructions with optimal limb and implant alignment, durable implant fixation, and functional outcomes that increasingly approach those of primary Total Knee Arthroplasty (TKA).

The objective of this study is to demonstrate statistically significant improvements in the original Knee Society Clinical Score (KSCS) from baseline to 1 and 2 years in subjects using the LEGION™ Hinge Knee System. The focus of the 1 and 2 year analyses will be on safety and efficacy. The 5 year analysis will focus on survivorship and safety.

Inclusion Criteria:

• Subject has gross knee instability resulting from loss of collateral ligament function, gross bone loss, comminuted fractures of the proximal tibia or distal femur, rheumatoid arthritis, post-traumatic arthritis, osteoarthritis, degenerative arthritis, failed osteotomies, unicompartmental replacement or total knee replacement, or absent or incompetent posterior cruciate ligament and one or both of the collateral ligaments
• Subject has a failed primary or revision knee replacement
• Subject is 18-80 years of age
• Subject is skeletally mature in Investigator's judgment i.e., subject is not actively growing or does not have immature bones for any reason
• Subject has met an acceptable preoperative medical clearance and is free of or treated for cardiac, pulmonary, hematological, infection or other conditions that would pose excessive operative risk
• Subject is willing to sign and date an IRB/EC-approved consent form
• Subject plans to be available through the five (5) year postoperative follow-up
• If of child bearing potential, Subject reports she is not pregnant nor plans to become pregnant during the study
• Subject agrees to follow the study protocol

Exclusion Criteria:

• Subject is receiving the study device as a primary knee replacement
• Subject has presence of malignant tumor, metastatic, or neoplastic disease
• Subject is not expected to return to normal ambulatory function (i.e., morbid obesity or other limiting co-morbidities)
• Subject is pregnant or plans to become pregnant during the course of the study
• Subject has conditions that may interfere with the revision arthroplasty survival or outcome (i.e., Paget's or Charcot-Marie-Tooth disease, vascular insufficiency, muscular atrophy, uncontrolled diabetes, moderate to severe renal insufficiency or neuromuscular disease)
• Subject has known (Subject reported) metal hypersensitivity
• Subject has an emotional or neurological condition that would pre-empt their ability or willingness to participate in this study
• Subject has BMI>45
• Subject is participating in any other pharmaceutical, biologic, or medical device clinical investigation or has been treated with an investigational product in the past 30 days
• Subject is facing current or impending incarceration
• Subject is not a good candidate for the study based on Investigator opinion

Patients requiring a revision total knee arthroplasty (TKA) using the LEGION Hinge Total Knee system.