My 10 month old dtr appears to be unable to actively extend her 2nd digit at the dip jt. i am able to passively extend it fully. there is no signs of trauma or injury. what could this be?

See pediatrician: Was there past trauma, bruising, swelling of the digit? An avulsion fracture with separation of the extensor digitorum from its insertion on the distal phalanx can happen from a blow to the tip of the finger such as from catching a ball. Please take your baby to the pediatrician for an evaluation and referral ASAP. I am assuming this is a new problem.

Could be injury: If this is a new finding, your child may have a tendon or subtle bone injury at the DIP. I suggest you have her seen and she may require Xrays to exclude a small fracture or dislocation.