Ellipse Intramedullary Nail High Tibial Osteotomy Study

Inclusion Criteria: 1. Patient has standing varus malalignment benefitting from high tibial osteotomy correction 2. Patient is diagnosed with current osteoarthritis of the knee 3. Patient is eighteen years of age or greater 4. Patient is a candidate to be implanted with an Ellipse IM HTO System 5. If female of childbearing potential, patient presents with a negative pregnancy test and agrees to employ adequate birth control measures for the duration of the study 6. Patient understands and accepts the obligation to comply with the required follow-up visits and is logistically able to meet all study requirements 7. Patient signs informed consent for the use of their personal private data Exclusion Criteria: 1. Patient declines to sign informed consent for the use of their personal private data 2. Varus deformity greater than 10° 3. Flexion contracture greater than 15° 4. Knee flexion under 90° 5. Medial/lateral tibial subluxation over 1 cm 6. Medial bone loss of over 3 mm 7. Inflammatory arthritis 8. Arthritis in the lateral compartment 9. Patella baja 10. Weight over 114 kg 11. Severe patellofemoral symptoms 12. Unaddressed ligamentous instability 13. Fixed flexion contracture 14. Known or suspected osteoporosis or osteopenia based on medical history and radiographic images 15. Current use of nicotine products. 16. Requires other surgical procedures at the time of the HTO surgery