Rickets is a bone disorder in babies and young children where the bones become soft and weak, leading to skeletal deformities like bowed legs and a misshapen skull. It happens when a child’s body doesn’t have enough of the minerals needed to build hard, strong bones, most often because of a vitamin D deficiency. While rickets was once considered a disease of the past, it still occurs today, particularly in breastfed infants who don’t receive vitamin D supplements.
How Rickets Affects Growing Bones
Children’s bones grow from areas called growth plates, which are bands of developing tissue near the ends of long bones. For these growth plates to work properly, the body needs adequate phosphorus. Low phosphorus is the common thread in all forms of rickets. Without enough of it, cells in the growth plate that are supposed to die off and be replaced by hard bone instead pile up, creating soft, poorly mineralized tissue.
Vitamin D plays a central role because it controls how well your baby’s intestines absorb calcium and phosphorus from food or formula. When vitamin D is too low, calcium absorption drops. The body then pulls calcium from the bones to keep blood levels stable, which further weakens the skeleton. The result is bones that bend under normal weight-bearing instead of staying rigid.
Signs to Look For
Rickets often develops gradually, and the earliest signs can be subtle. One of the first things parents or doctors may notice is craniotabes, a softening of the skull bones that feels like pressing on a ping-pong ball. In young infants, the soft spot on top of the head may be larger than expected or slow to close.
As the condition progresses, more visible skeletal changes appear:
- Widened wrists and ankles. The ends of the bones flare outward where the growth plates are expanding with soft, unmineralized tissue.
- Rachitic rosary. Bead-like bumps along the front of the rib cage where the ribs meet the cartilage of the breastbone.
- Harrison groove. A horizontal line or indentation across the lower chest, caused by the diaphragm pulling on softened ribs.
- Bowed legs or knock knees. Once a child starts standing and walking, soft leg bones curve under body weight.
- Delayed growth. Children with rickets are often shorter than expected for their age.
Beyond the skeleton, babies with severe vitamin D deficiency can develop dangerously low blood calcium, which may cause muscle spasms, twitching, or seizures. These episodes can happen before any visible bone changes appear, making them one of the more alarming early presentations.
What Puts a Baby at Risk
Exclusive breastfeeding without vitamin D supplementation is the single most common setup for nutritional rickets in developed countries. Breast milk is excellent nutrition in nearly every way, but it contains very little vitamin D, typically not enough to meet a baby’s needs on its own.
Several other factors raise the risk. Babies with darker skin produce less vitamin D from sunlight because higher melanin levels slow the skin’s ability to synthesize it. Families living at northern latitudes or in cloudy climates face the same challenge, especially during winter months. Premature babies are also more vulnerable because they had less time in the womb to build up vitamin D stores from their mother.
A mother’s own vitamin D status matters too. A baby born to a mother with serious vitamin D deficiency can arrive with rickets already present or develop symptoms within the first few months of life. This is more common than many parents realize, since vitamin D deficiency in adults often goes undiagnosed.
How Rickets Is Diagnosed
If a doctor suspects rickets based on a physical exam, they’ll typically order blood tests and X-rays. The blood work looks for a few characteristic patterns: phosphorus levels are almost always low, and a bone enzyme called alkaline phosphatase is elevated, reflecting the body’s unsuccessful attempts to mineralize bone. Vitamin D levels are usually low, though doctors don’t always need to measure them directly if the other markers are clear.
X-rays of the wrists or knees are often the most definitive tool. In a healthy child, the ends of the bones look smooth and well-defined. In rickets, those same areas show widening, cupping (a scooped-out appearance), and fraying (an irregular, brush-like edge). These changes are distinctive enough that an experienced doctor can often confirm the diagnosis from a single set of images.
Treatment and Recovery
Nutritional rickets responds well to treatment, and most babies improve significantly within weeks to months. The core approach is replacing the missing vitamin D, sometimes alongside calcium supplements. Doctors may prescribe daily vitamin D doses given over two to three months, or in some cases, a single large dose. The specific approach depends on the severity and the child’s age.
Calcium supplementation helps when dietary intake is inadequate. Research has shown that a daily calcium intake of at least 1,000 mg leads to faster healing on X-rays compared to lower doses, though going above that amount doesn’t seem to add extra benefit.
Bone changes on X-rays typically start improving within a few weeks of treatment, and blood markers often normalize within one to two months. Skeletal deformities like mild bowing usually correct on their own as the child grows, especially if rickets is caught early. Severe bowing that persists after the underlying deficiency is corrected may eventually require surgical correction, but this is uncommon.
Preventing Rickets
Prevention is straightforward. The American Academy of Pediatrics recommends that all babies younger than 12 months receive 400 IU of vitamin D daily. For breastfed and partially breastfed infants, this supplementation should begin in the first few days of life. Formula-fed babies need a supplement too unless they’re consistently drinking at least 32 ounces of vitamin D-fortified formula per day.
Vitamin D drops designed for infants are widely available over the counter and easy to administer. A single drop per day is all most products require. This simple daily habit is the most reliable way to prevent rickets, since relying on sunlight alone is unreliable for infants. Dermatologists generally discourage direct sun exposure for babies under six months, and even for older infants, factors like skin tone, season, and geography make sun-based vitamin D production unpredictable.
Genetic Forms of Rickets
A small number of children develop rickets that isn’t caused by diet or sunlight at all. Hereditary hypophosphatemic rickets, sometimes called vitamin D-resistant rickets, is a genetic condition where the kidneys can’t hold onto phosphorus properly. Too much phosphorus gets flushed out through urine, leaving too little in the bloodstream for normal bone development. This happens because of overactivity of a protein that tells the kidneys to release phosphorus instead of reabsorbing it.
Children with this form of rickets don’t respond to standard vitamin D supplements the way nutritionally deficient children do. They need specialized treatment aimed at replacing phosphorus and using active forms of vitamin D. If your child has been treated for rickets but isn’t improving as expected, genetic testing may help identify whether an inherited form is responsible.