Medical Conditions

Septic Arthritis (Joint Infection) in Children

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published AAP, OrthoInfo, NIH guidelines

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If your baby has been diagnosed with or you suspect septic arthritis (joint infection) in children, here is what the evidence says.

The short answer

Septic arthritis is a bacterial infection inside a joint, most commonly the hip or knee in children. It presents with fever, extreme pain with any movement of the joint, swelling and warmth over the joint, and refusal to move the affected limb. Septic arthritis is a medical emergency because bacteria can rapidly destroy joint cartilage within hours to days. Treatment requires urgent surgical drainage (or needle aspiration) of the infected joint combined with IV antibiotics. With prompt treatment, most children recover fully.

Key takeaways

  • Septic arthritis is a bacterial infection inside a joint, most commonly the hip or knee in children. It presents with fever, extreme pain with any movement of the joint, swelling and warmth over the joint, and refusal to move the affected limb. Septic arthritis is a medical emergency because bacteria can rapidly destroy joint cartilage within hours to days. Treatment requires urgent surgical drainage (or needle aspiration) of the infected joint combined with IV antibiotics. With prompt treatment, most children recover fully.
  • Usually normal when: Your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign)
  • Call your doctor if: Your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage
  • Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

This is one of the most common questions parents ask. Searching for answers means you care.

What Parents Should Know

According to AAP, OrthoInfo, NIH guidelines, septic arthritis is a bacterial infection inside a joint, most commonly the hip or knee in children. It presents with fever, extreme pain with any movement of the joint, swelling and warmth over the joint, and refusal to move the affected limb. Septic arthritis is a medical emergency because bacteria can rapidly destroy joint cartilage within hours to days. Treatment requires urgent surgical drainage (or needle aspiration) of the infected joint combined with IV antibiotics. With prompt treatment, most children recover fully. At 0-3 months, neonatal septic arthritis is a serious condition that can be difficult to diagnose because newborns cannot verbalize pain. Signs include irritability, poor feeding, decreased movement of the affected limb (pseudoparalysis), swelling around a joint (the hip is most commonly affected), and fever, though neonates may not always mount a fever. The infection often spreads from the bloodstream. Common organisms include Group B Streptococcus, Staphylococcus aureus, and gram-negative bacteria. Any newborn with unexplained irritability, limb swelling, or refusal to move an extremity needs urgent evaluation. It is generally considered normal when your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign). However, you should contact your pediatrician promptly if your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign)
Your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage
Your child was diagnosed with transient synovitis of the hip (a self-limited inflammatory condition without fever or high inflammatory markers)
Your infant or baby is febrile, extremely irritable, and holds one limb still or screams when you try to move it, especially during diaper changes, which may indicate septic arthritis of the hip and requires emergency evaluation
Your child has joint clicking or popping without pain, swelling, or fever, which is usually from normal ligament movement
Your child has a persistently swollen or warm joint without a clear injury, even without fever
Your child bumped a knee or ankle and has mild bruising and tenderness but no fever, warmth, or significant swelling of the joint
Your child limps or refuses to bear weight for more than a day after a viral illness

By Age

What to expect by age

0-3 months

Neonatal septic arthritis is a serious condition that can be difficult to diagnose because newborns cannot verbalize pain. Signs include irritability, poor feeding, decreased movement of the affected limb (pseudoparalysis), swelling around a joint (the hip is most commonly affected), and fever, though neonates may not always mount a fever. The infection often spreads from the bloodstream. Common organisms include Group B Streptococcus, Staphylococcus aureus, and gram-negative bacteria. Any newborn with unexplained irritability, limb swelling, or refusal to move an extremity needs urgent evaluation.

3-12 months

Infants with septic arthritis typically present with fever, extreme irritability when the joint is moved (especially during diaper changes for hip infections), swelling, and refusal to move the limb. The hip is the most commonly affected joint in this age group and can be difficult to assess because hip swelling is deep and may not be visible. An infant who cries inconsolably when you try to move their leg, holds the hip in a flexed and externally rotated position, or refuses to bear weight on a leg should be evaluated emergently. Ultrasound can detect fluid in the hip joint, and joint aspiration confirms the diagnosis.

1-3 years

Toddlers with septic arthritis often present with a limp or sudden refusal to walk, fever, and a hot, swollen, painful joint. The knee and hip are the most commonly affected joints. Staphylococcus aureus remains the leading cause, but Kingella kingae is an increasingly recognized pathogen in children under 5 years old. Kocher criteria (fever, elevated ESR, elevated white blood cell count, and refusal to bear weight) help distinguish septic arthritis from the more benign transient synovitis. Surgical drainage or aspiration of the infected joint, combined with IV antibiotics, is the standard treatment.

3-5 years

Older children can usually point to the painful joint and describe their symptoms. Presentation includes fever, a joint that is swollen, red, hot, and exquisitely painful to touch or move, and refusal to use the limb. Staphylococcus aureus (including MRSA in some regions) is the most common cause. Blood tests, joint aspiration, and imaging (ultrasound or MRI) guide the diagnosis. Treatment involves urgent joint drainage and at least 3-4 weeks of antibiotics. When treated promptly, long-term outcomes are excellent, though follow-up is important to monitor for growth plate damage.

What to Tell Your Pediatrician

  • Describe when you first noticed septic arthritis (joint infection) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has a persistently swollen or warm joint without a clear injury, even without fever.
  • Mention if your child limps or refuses to bear weight for more than a day after a viral illness.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign)
  • Your child was diagnosed with transient synovitis of the hip (a self-limited inflammatory condition without fever or high inflammatory markers)
  • Your child has joint clicking or popping without pain, swelling, or fever, which is usually from normal ligament movement
  • Your child bumped a knee or ankle and has mild bruising and tenderness but no fever, warmth, or significant swelling of the joint
Mention at your next visit when...
  • Your child has a persistently swollen or warm joint without a clear injury, even without fever
  • Your child limps or refuses to bear weight for more than a day after a viral illness
  • Your child has recurring joint pain or swelling in the same or multiple joints, which could indicate other conditions such as juvenile idiopathic arthritis
Act now when...
  • Your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage
  • Your infant or baby is febrile, extremely irritable, and holds one limb still or screams when you try to move it, especially during diaper changes, which may indicate septic arthritis of the hip and requires emergency evaluation

What You Can Do at Home

  • Keep track of when you notice septic arthritis (joint infection) in children — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign) — this is generally within the range of normal.
  • At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage.

My Baby or Toddler Is Limping

A limp in a baby or toddler always deserves medical attention, as young children cannot reliably tell you where it hurts. The most common cause in toddlers is a minor injury such as a 'toddler's fracture' (a subtle shin bone crack) or muscle strain. However, limping can also indicate infection in a joint or bone, hip problems, or other conditions that need prompt evaluation.

Bone Infection (Osteomyelitis) in Children

Osteomyelitis is a bacterial infection of the bone, most commonly caused by Staphylococcus aureus. In children, it typically affects the long bones (femur, tibia, humerus) and presents with localized bone pain, swelling, warmth, fever, and refusal to use the affected limb. Diagnosis involves blood tests, X-rays, and MRI (the most sensitive imaging test). Treatment requires prolonged intravenous antibiotics, typically for several weeks, and sometimes surgical drainage. Early treatment leads to excellent outcomes.

My Toddler Has Swollen Joints

Swollen joints in toddlers should always be evaluated by a pediatrician. While minor swelling after an injury can be normal, persistent or unexplained joint swelling may indicate juvenile idiopathic arthritis (JIA), infection, or other conditions that require prompt treatment. JIA affects about 1 in 1,000 children and is very treatable when caught early.

Triage

Fever Decision Tree

Step-by-step guidance for evaluating your baby's fever by age and temperature.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is septic arthritis (joint infection) in children normal?
Septic arthritis is a bacterial infection inside a joint, most commonly the hip or knee in children. It presents with fever, extreme pain with any movement of the joint, swelling and warmth over the joint, and refusal to move the affected limb. Septic arthritis is a medical emergency because bacteria can rapidly destroy joint cartilage within hours to days. Treatment requires urgent surgical drainage (or needle aspiration) of the infected joint combined with IV antibiotics. With prompt treatment, most children recover fully.
When should I call the doctor about septic arthritis (joint infection) in children?
Your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage Your infant or baby is febrile, extremely irritable, and holds one limb still or screams when you try to move it, especially during diaper changes, which may indicate septic arthritis of the hip and requires emergency evaluation
When is septic arthritis (joint infection) in children normal?
Your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign) Your child was diagnosed with transient synovitis of the hip (a self-limited inflammatory condition without fever or high inflammatory markers) Your child has joint clicking or popping without pain, swelling, or fever, which is usually from normal ligament movement
What causes septic arthritis (joint infection) in children?
Septic arthritis is a bacterial infection inside a joint, most commonly the hip or knee in children. It presents with fever, extreme pain with any movement of the joint, swelling and warmth over the joint, and refusal to move the affected limb. Septic arthritis is a medical emergency because bacteria can rapidly destroy joint cartilage within hours to days. Treatment requires urgent surgical drainage (or needle aspiration) of the infected joint combined with IV antibiotics. With prompt treatment, most children recover fully. Common explanations include: Your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign). Your child was diagnosed with transient synovitis of the hip (a self-limited inflammatory condition without fever or high inflammatory markers).
What should I mention to my pediatrician about septic arthritis (joint infection) in children?
You should mention septic arthritis (joint infection) in children at your next visit if: Your child has a persistently swollen or warm joint without a clear injury, even without fever. Your child limps or refuses to bear weight for more than a day after a viral illness. Your child has recurring joint pain or swelling in the same or multiple joints, which could indicate other conditions such as juvenile idiopathic arthritis.
Is septic arthritis (joint infection) in children normal at 0-3 months?
Neonatal septic arthritis is a serious condition that can be difficult to diagnose because newborns cannot verbalize pain. Signs include irritability, poor feeding, decreased movement of the affected limb (pseudoparalysis), swelling around a joint (the hip is most commonly affected), and fever, though neonates may not always mount a fever. The infection often spreads from the bloodstream. Common organisms include Group B Streptococcus, Staphylococcus aureus, and gram-negative bacteria. Any newborn with unexplained irritability, limb swelling, or refusal to move an extremity needs urgent evaluation.
Is septic arthritis (joint infection) in children normal at 3-12 months?
Infants with septic arthritis typically present with fever, extreme irritability when the joint is moved (especially during diaper changes for hip infections), swelling, and refusal to move the limb. The hip is the most commonly affected joint in this age group and can be difficult to assess because hip swelling is deep and may not be visible. An infant who cries inconsolably when you try to move their leg, holds the hip in a flexed and externally rotated position, or refuses to bear weight on a leg should be evaluated emergently. Ultrasound can detect fluid in the hip joint, and joint aspiration confirms the diagnosis.
Should I go to the ER for septic arthritis (joint infection) in children?
Seek emergency care if your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage, or if your infant or baby is febrile, extremely irritable, and holds one limb still or screams when you try to move it, especially during diaper changes, which may indicate septic arthritis of the hip and requires emergency evaluation. When in doubt, call your pediatrician's after-hours line for guidance.
Does septic arthritis (joint infection) in children go away on its own?
In many cases, septic arthritis (joint infection) in children resolves on its own, especially when your child has mild joint aches or stiffness during a viral illness that resolves within a few days (reactive arthritis associated with viruses is common and benign). By 3-5 years, older children can usually point to the painful joint and describe their symptoms. Presentation includes fever, a joint that is swollen, red, hot, and exquisitely painful to touch or move, and refusal to use the limb. Staphylococcus aureus (including MRSA in some regions) is the most common cause. Blood tests, joint aspiration, and imaging (ultrasound or MRI) guide the diagnosis. Treatment involves urgent joint drainage and at least 3-4 weeks of antibiotics. When treated promptly, long-term outcomes are excellent, though follow-up is important to monitor for growth plate damage.
AAPORTHOINFONIH

References

  1. [1]American Academy of Pediatrics. Septic Arthritis (Bacterial Joint Infection). Red Book: Report of the Committee on Infectious Diseases, 2021. AAP
  2. [2]American Academy of Orthopaedic Surgeons. Septic Arthritis. OrthoInfo, 2022. OrthoInfo
  3. [3]National Institutes of Health. Septic Arthritis. MedlinePlus, 2023. NIH

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Septic Arthritis (Joint Infection) in Children.

Things to mention

  • Describe when you first noticed septic arthritis (joint infection) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has a persistently swollen or warm joint without a clear injury, even without fever.
  • Mention if your child limps or refuses to bear weight for more than a day after a viral illness.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child has a persistently swollen or warm joint without a clear injury, even without fever
  • Your child limps or refuses to bear weight for more than a day after a viral illness
  • Your child has recurring joint pain or swelling in the same or multiple joints, which could indicate other conditions such as juvenile idiopathic arthritis

Urgent signs to report immediately

  • Your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage
  • Your infant or baby is febrile, extremely irritable, and holds one limb still or screams when you try to move it, especially during diaper changes, which may indicate septic arthritis of the hip and requires emergency evaluation

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Fever TriageWell-Baby Visit PrepMedicine Dosage CalculatorBaby Tracker

Bottom line

Most cases of septic arthritis (joint infection) in children are normal. Talk to your pediatrician if your child has a hot, swollen, painful joint with fever and refuses to move the limb, which is a medical emergency requiring immediate evaluation for septic arthritis, as delays in treatment can lead to permanent joint damage.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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A limp in a baby or toddler always deserves medical attention, as young children cannot reliably tell you where it hurts. The most common cause in toddlers is a minor injury such as a 'toddler's fracture' (a subtle shin bone crack) or muscle strain. However, limping can also indicate infection in a joint or bone, hip problems, or other conditions that need prompt evaluation.

Bone Infection (Osteomyelitis) in Children

Osteomyelitis is a bacterial infection of the bone, most commonly caused by Staphylococcus aureus. In children, it typically affects the long bones (femur, tibia, humerus) and presents with localized bone pain, swelling, warmth, fever, and refusal to use the affected limb. Diagnosis involves blood tests, X-rays, and MRI (the most sensitive imaging test). Treatment requires prolonged intravenous antibiotics, typically for several weeks, and sometimes surgical drainage. Early treatment leads to excellent outcomes.

My Toddler Has Swollen Joints

Swollen joints in toddlers should always be evaluated by a pediatrician. While minor swelling after an injury can be normal, persistent or unexplained joint swelling may indicate juvenile idiopathic arthritis (JIA), infection, or other conditions that require prompt treatment. JIA affects about 1 in 1,000 children and is very treatable when caught early.

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