My 14 year old is feeling a popping sensation in her Achilles tendon area last night and today. She says it doesn't hurt, it just feels weird.

She's not very active right now so I doubt it's overuse, but could it be under use? For a few months she was into an outdoor exercise and barefoot running group with me, but when the cold weather hit it went to the wayside and for the past few weeks she's back to being pretty much a lump on the couch most days.

Any suggestions?