An auto-flex knee brace that employs an extension spring defined as a flexible hinge, which determines different modes of configuration to alleviate medial and lateral compartmental osteoarthritis of a knee of a patient is disclosed. The auto-flex knee brace comprises an upper thigh cuff, a lower thigh cuff, a flexible strap arrangement and at least one spring column assembly. The upper thigh cuff is positioned substantially above knee for encircling an upper part of leg of a user and the lower thigh cuff is positioned substantially below the knee for encircling a lower part of the leg of the user. The flexible strap arrangement includes a first strap means and a second strap means that securely tied around the upper thigh cuff and the lower thigh cuff. The at least one spring column assembly is adaptable for releasably coupling the upper thigh cuff and the lower thigh cuff.