I feel clicking under the left anterolateral aspect of my ribcage. The clicking happens when I flex my trunk forward, side-bend to the left, and rotate my trunk to the right. It is not painful and has been happening for approximately 1 year. When I palpate along the lower borders of my rib cage, it feels almost like there is an extra rib on the left - something fairly firm and superficial. Is this likely a muscular problem, or something I should be concerned about? Any advice would be appreciated. Thank you.