My Baby Seems Too Stiff (Hypertonia)
The short answer
Hypertonia means your baby's muscles feel unusually tight or stiff, making it hard to bend or move their limbs. While some stiffness can be normal during certain movements (like when a baby is startled or upset), persistent stiffness at rest warrants evaluation. Early identification and physical therapy can make a significant difference.
By Age
What to expect by age
Newborns naturally have some degree of flexor tone, meaning their arms and legs tend to curl inward. This is different from hypertonia, where the limbs feel rigid and resist being moved. Signs to watch for include a baby who feels like a board when you pick them up, whose legs scissor or cross when held upright, or who arches their back strongly and frequently. Some stiffness during crying or startling is normal, but stiffness at rest is not.
As normal newborn flexor tone decreases, you should be able to gently extend your baby's arms and legs without much resistance. A baby with hypertonia may still have tightly fisted hands past 3 months, resist having their arms or legs straightened, or arch their back when you try to hold them in a seated position. These babies may have difficulty with tummy time because they cannot relax enough to push up comfortably.
Babies with hypertonia may have difficulty reaching motor milestones like sitting, crawling, and grasping objects. Their movements may look stiff or jerky rather than smooth. You might notice that their legs feel very tight when you try to open them for a diaper change, or that they consistently point their toes. Physical therapy at this stage focuses on stretching, positioning, and encouraging relaxed movement patterns.
Persistent hypertonia affects walking and other gross motor skills. A toddler with high muscle tone may walk stiffly, have difficulty with balance, or walk on their toes. Ongoing physical therapy is important, and your pediatrician may refer you to a pediatric neurologist to determine the underlying cause. Many children with mild hypertonia respond very well to therapy and make excellent progress.
What Should You Do?
When to take action
- Your baby stiffens briefly when startled, excited, or upset, but relaxes at rest.
- Your baby has some normal newborn flexor tone but you can gently extend their limbs without significant resistance.
- Your baby occasionally arches their back during fussiness or gas but is otherwise relaxed and moves freely.
- Your baby feels strong and firm but is meeting motor milestones on time.
- Your baby's limbs feel consistently stiff and resist gentle bending, even when your baby is calm and relaxed.
- Your baby's hands are tightly fisted past 3-4 months of age and they have difficulty opening them to grasp objects.
- Your baby arches their back frequently during feeding or when held, and this seems involuntary.
- Your baby's whole body stiffens and their legs scissor when held upright, or they feel like a rigid board when picked up.
- Your baby has stiffness accompanied by difficulty feeding, breathing problems, or seizure-like episodes.
Sources
Related Resources
Related Physical Concerns
My Baby Seems to Use One Side More Than the Other
Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.
My Baby Curls Their Toes
Toe curling is very common in babies and is usually caused by the plantar grasp reflex, which is a normal newborn reflex that causes toes to curl when the sole of the foot is touched. This reflex typically fades by 9-12 months. Occasional toe curling during standing or walking is also normal as babies figure out their balance. Persistent, tight toe curling past 12 months may warrant a mention to your pediatrician.
My Baby Favors One Leg
Babies should use both legs roughly equally when kicking, crawling, and eventually walking. If your baby consistently favors one leg or seems to avoid using the other, it is worth having your pediatrician take a look. The cause is often something simple and treatable, like a minor hip or muscle issue, but early evaluation helps ensure the best outcome.
My Baby Gets Hiccups a Lot
Hiccups are extremely common in babies, especially newborns, and are almost always completely harmless. They happen because your baby's diaphragm is still developing and gets a little jumpy when their tiny stomach fills up or air gets swallowed. Most babies outgrow frequent hiccupping by 6-9 months.
My Baby Has Jerky Movements
Newborns and young babies often have jerky, uncoordinated movements because their nervous systems are still developing. What looks like random flailing is actually your baby learning how their body works. These movements typically become smoother and more controlled by 3-4 months as motor skills mature.
Baby Not Bearing Weight on Arms
Bearing weight on the arms is a gradual skill that develops during the first 6 months. Babies first prop up on their forearms around 2 to 4 months, then progress to pushing up on extended arms by 5 to 6 months. Regular tummy time is the best way to build this strength, even if your baby protests at first.