Little Jayden James is an 8-month-old on the move. And the fact that his mom, Kim Brenninkmeyer, can keep up is amazing.
When Jayden was born, she found the area from her wrist to thumb was in constant pain.
"Any kind of motion where I had to stretch was very painful. It just felt like it was tearing, ripping, burning," said Brenninkmeyer.
"She asked very frankly: 'Is this going to happen every time I have a child? I don't know if I can go through this,'" said Dr. David Maine, director of the Center for Interventional Pain Medicine at Mercy Medical Center in Baltimore.
Maine knew the cause: so-called "Mommy Thumb," a new term for overuse injury. The true name: De Quervain's tenosynovitis. It comes with the scooping, holding and lifting that new moms aren't used to.
"I've talked to friends who've had babies and they've said 'Oh, I had that too,' and no one knew what it was," said Brenninkmeyer.
Experts say one-quarter to one-half of new mothers now get symptoms. Causes include heavier children, as more than 10 percent of 2-year-olds are now overweight. Plus more older mothers are having kids, and more people are using thumb-numbing smartphones too.
"All that can create this overuse of these tendons along the base of the thumb and create tendonitis, essentially," said Maine.
A new mom at 40, Brenninkmeyer got cortisone shots, which are 90 percent effective. Now she can keep up with her son with no problems.
"So about two weeks I was pain-free, which was just such a relief," said Brenninkmeyer.
If cortisone shots don't work, surgery is an option.
"Mommy Thumb" issues may also start to present themselves in the third trimester of pregnancy.