This study is designed as a prospective, multicenter, open-label, single arm, pilot study. Eligible subjects with symptomatic osteoarthritis of the medial compartment of the knee will be enrolled in the study and will receive the Atlas Knee Implant. The study population will consist of adult subjects age 25 to 80 years, with a diagnosis of medial knee osteoarthritis (Kellgen and Lawrence Grades 1-4, except those with bony erosions) and has pain in the study knee demonstrated as an overall WOMAC pain score of ≥ 40 (scale 0-100).