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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pediatric Rheumatology · Enthesitis-Related Arthritis

More Than 'Growing Pains': Recognizing the Symptoms of ERA-JIA

At a Glance

Enthesitis-Related Arthritis (ERA) causes inflammation where tendons attach to bone, often mimicking sports injuries in active children. Unlike overuse injuries that worsen with activity, ERA causes severe morning stiffness that improves with movement. Early MRI screening helps detect hidden inflammation.

Distinguishing between a sports injury and Enthesitis-Related Arthritis (ERA) can be challenging because both often affect active children in similar locations. However, the underlying cause of the pain is very different. While a sports injury is typically caused by physical stress or “wear and tear,” ERA is caused by the immune system attacking specific parts of the body [1][2].

What is Enthesitis?

The hallmark of ERA is enthesitis—inflammation at the entheses, which are the specific points where tendons or ligaments attach to the bone [3].

In typical arthritis, the inflammation is inside the joint space (synovitis). In ERA, the pain often feels like it is “on” the bone or just outside the joint [4]. Common locations for enthesitis include:

  • The Heels: Where the Achilles tendon attaches to the back of the heel or the plantar fascia attaches to the bottom of the foot [5].
  • The Knees: At the base of the kneecap (patellar tendon) or the bony bump just below it (tibial tuberosity) [5].
  • The Hips and Pelvis: Along the crest of the hip bone or where the hamstrings attach [6].

ERA vs. Common Sports Injuries

Because ERA often starts in late childhood, it is frequently mistaken for common “overuse” syndromes. Here is how they generally differ:

Feature ERA (Inflammatory) Osgood-Schlatter / Sever’s (Mechanical)
Morning Symptoms Severe stiffness and pain after waking [7]. Usually no stiffness; feels better after rest.
Effect of Exercise Pain often improves with movement or light activity [8]. Pain worsens during or immediately after activity.
Multiple Sites May affect several different tendons or joints at once [3]. Usually limited to one specific overworked area.
Response to Rest Stiffness and pain often worsen after long periods of sitting [8]. Symptoms improve significantly with rest and ice.

Recognizing Inflammatory Back Pain

As ERA progresses, it can involve the spine and the sacroiliac (SI) joints—the joints that connect the lower spine to the pelvis [9]. This is known as inflammatory back pain (IBP).

Unlike a typical muscle strain, IBP has very specific characteristics:

  • The “Morning Log” Feeling: A child may feel like they cannot bend or move easily for 30 minutes or more after waking up [7].
  • Alternating Buttock Pain: Pain that may shift from the left side of the buttocks to the right side [10].
  • Night Pain: Pain that is severe enough to wake the child up in the middle of the night [11].

The Role of “Silent” Inflammation

It is important to know that sacroiliitis (inflammation of the SI joints) can be “silent.” Studies have shown that between 34% and 62% of children with ERA have active inflammation on an MRI, even if they have not yet complained of back pain [12][13]. Because of this, many pediatric rheumatologists use MRI early in the diagnostic process to look for subclinical inflammation that cannot be seen on a regular X-ray [14][15]. Identifying this early allows for more targeted treatment to prevent long-term joint damage [16][17].

Common questions in this guide

How can I tell if my child's joint pain is from ERA or a sports injury?
Pain from ERA often causes severe morning stiffness and improves with movement or light activity. In contrast, common sports overuse injuries typically worsen during or immediately after activity and feel better with rest and ice.
What is enthesitis?
Enthesitis is inflammation at the specific points where tendons or ligaments attach to the bone, known as entheses. In children with ERA, this most commonly causes pain on the bone just outside the joints in the heels, knees, and hips.
What does inflammatory back pain feel like?
Inflammatory back pain in children often feels like a 'morning log,' causing severe stiffness that lasts for 30 minutes or more after waking up. It can also cause alternating buttock pain or pain severe enough to wake the child up at night.
Why would my child need an MRI if they don't have back pain?
Many children with ERA have silent inflammation in their sacroiliac joints before they ever experience noticeable back pain. Pediatric rheumatologists use MRIs to detect this hidden inflammation early so treatment can begin before long-term joint damage occurs.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.How do you distinguish my child's heel or knee pain from a typical overuse injury like Sever's or Osgood-Schlatter disease?
  2. 2.Are the locations where my child is experiencing pain consistent with enthesitis, and should we consider an ultrasound to check for subclinical inflammation?
  3. 3.If my child has no back pain, is it still necessary to screen for sacroiliitis with an MRI?
  4. 4.What features of my child's stiffness suggest inflammatory back pain rather than a muscle strain or 'growing pains'?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Enthesitis-Related Juvenile Idiopathic Arthritis.

    Rosenthal A, Janow G

    Pediatrics in review 2019; (40(5)):256-258 doi:10.1542/pir.2017-0177.

    PMID: 31043447
  2. 2

    Juvenile idiopathic arthritis in a center in the Western Anatolia region in Turkey.

    Yener GO, Tekin ZE, Girişgen İ, et al.

    Turk pediatri arsivi 2020; (55(2)):157-165 doi:10.14744/TurkPediatriArs.2019.69320.

    PMID: 32684761
  3. 3

    Enthesitis-related arthritis: current perspectives.

    Mistry RR, Patro P, Agarwal V, Misra DP

    Open access rheumatology : research and reviews 2019; (11()):19-31 doi:10.2147/OARRR.S163677.

    PMID: 30774484
  4. 4

    Inflammatory ankle MRI findings in pediatric and young adult patients with familial Mediterranean fever: a comparison with juvenile idiopathic arthritis and chronic nonbacterial osteomyelitis.

    Kraus M, Cohen I, Kalderon E, et al.

    Skeletal radiology 2026; doi:10.1007/s00256-026-05153-y.

    PMID: 41639256
  5. 5

    Characteristics and Course of Enthesitis in a Juvenile Idiopathic Arthritis Inception Cohort.

    Rumsey DG, Guzman J, Rosenberg AM, et al.

    Arthritis care & research 2018; (70(2)):303-308 doi:10.1002/acr.23256.

    PMID: 28426894
  6. 6

    Diagnositic value of pelvic enthesitis on MRI of the sacroiliac joints in enthesitis related arthritis.

    Herregods N, Dehoorne J, Pattyn E, et al.

    Pediatric rheumatology online journal 2015; (13(1)):46 doi:10.1186/s12969-015-0045-5.

    PMID: 26554668
  7. 7

    Association between inflammatory back pain features, acute and structural sacroiliitis on MRI, and the diagnosis of spondyloarthritis.

    Kivity S, Gofrit SG, Baker FA, et al.

    Clinical rheumatology 2019; (38(6)):1579-1585 doi:10.1007/s10067-019-04432-5.

    PMID: 30628016
  8. 8

    Differences in topographical location of sacroiliac joint MRI lesions in patients with early axial spondyloarthritis and mechanical back pain.

    Kiil RM, Mistegaard CE, Loft AG, et al.

    Arthritis research & therapy 2022; (24(1)):75 doi:10.1186/s13075-022-02760-7.

    PMID: 35331320
  9. 9

    Does sacroiliitis is a mandatory criterion for enthesitis-related arthritis diagnosis?

    Lassoued Ferjani H, Kharrat L, Ben Nessib D, et al.

    Reumatologia clinica 2024; (20(4)):187-192 doi:10.1016/j.reumae.2023.12.008.

    PMID: 38644029
  10. 10

    Clinical predictors of magnetic resonance imaging-detected sacroiliitis in children with enthesitis related arthritis.

    Bou Antoun M, Adamsbaum C, Semerano L, et al.

    Joint bone spine 2017; (84(6)):699-702 doi:10.1016/j.jbspin.2017.07.003.

    PMID: 28757344
  11. 11

    Prevalence of sacroiliitis and acute and structural changes on MRI in patients with psoriatic arthritis.

    Braga MV, de Oliveira SC, Vasconcelos AHC, et al.

    Scientific reports 2020; (10(1)):11580 doi:10.1038/s41598-020-68456-7.

    PMID: 32665619
  12. 12

    Outcomes in Juvenile-Onset Spondyloarthritis.

    Smith JA, Burgos-Vargas R

    Frontiers in medicine 2021; (8()):680916 doi:10.3389/fmed.2021.680916.

    PMID: 34124112
  13. 13

    Spinal involvement in juvenile idiopathic arthritis: what do we miss without imaging?

    Demir S, Ergen FB, Taydaş O, et al.

    Rheumatology international 2022; (42(3)):519-527 doi:10.1007/s00296-021-04890-8.

    PMID: 34115188
  14. 14

    Current Role of Conventional Radiography of Sacroiliac Joints in Adults and Juveniles with Suspected Axial Spondyloarthritis: Opinion from the ESSR Arthritis and Pediatric Subcommittees.

    Sudoł-Szopińska I, Herregods N, Zejden A, et al.

    Seminars in musculoskeletal radiology 2023; (27(5)):588-595 doi:10.1055/s-0043-1772169.

    PMID: 37816367
  15. 15

    Defining active sacroiliitis on MRI for classification of axial spondyloarthritis: update by the ASAS MRI working group.

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    Annals of the rheumatic diseases 2016; (75(11)):1958-1963 doi:10.1136/annrheumdis-2015-208642.

    PMID: 26768408
  16. 16

    Enthesitis-related arthritis is the most common category of juvenile idiopathic arthritis in Taiwan and presents persistent active disease.

    Shih YJ, Yang YH, Lin CY, et al.

    Pediatric rheumatology online journal 2019; (17(1)):58 doi:10.1186/s12969-019-0363-0.

    PMID: 31443722
  17. 17

    Capturing the enthesitis related arthritis contemporary profile of Caucasian patients in the era of biologics.

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    PMID: 32322980

This page explains the symptoms of ERA-JIA for educational purposes only. Always consult a pediatric rheumatologist to properly evaluate your child's joint pain or stiffness.

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