Transient synovitis is the most common cause of acute hip pain and limp in children aged 2 to 12 years. In a 2024 retrospective review, transient synovitis was the most common diagnosis in limping children.[1]Cristaldi S, Boni A, Ferro V, et al. Atraumatic limping child, a challenge for pediatricians: an observational age-related study in a pediatric emergency department. Children (Basel). 2024 Feb 2;11(2):185.
https://www.mdpi.com/2227-9067/11/2/185
http://www.ncbi.nlm.nih.gov/pubmed/38397297?tool=bestpractice.com
The mean age is 5 to 6 years, and up to 3% of children have an episode at some time during their childhood.[2]Krul M, van der Wouden JC, Schellevis FG, et al. Acute non-traumatic hip pathology in children: incidence and presentation in family practice. Fam Pract. 2010 Apr;27(2):166-70.
https://academic.oup.com/fampra/article/27/2/166/510395
http://www.ncbi.nlm.nih.gov/pubmed/20026553?tool=bestpractice.com
[3]Landin LA, Danielsson LG, Wattsgård C. Transient synovitis of the hip. Its incidence, epidemiology and relation to Perthes' disease. J Bone Joint Surg Br. 1987 Mar;69(2):238-42.
https://online.boneandjoint.org.uk/doi/abs/10.1302/0301-620X.69B2.3818754
http://www.ncbi.nlm.nih.gov/pubmed/3818754?tool=bestpractice.com
[4]Benoit J, El Khalifi S, Saoudi C, et al. Transient synovitis of the hip: development and validation of a new diagnostic algorithm. Acta Paediatr. 2024 Jun;113(6):1396-403.
https://onlinelibrary.wiley.com/doi/10.1111/apa.17144
http://www.ncbi.nlm.nih.gov/pubmed/38366676?tool=bestpractice.com
One large Dutch survey of children aged 0 to 14 years found that the incidence rate for all acute non-traumatic hip pathology was 148.1 per 100,000 person-years, and for transient synovitis this was 76.2 per 100,000 person-years.[2]Krul M, van der Wouden JC, Schellevis FG, et al. Acute non-traumatic hip pathology in children: incidence and presentation in family practice. Fam Pract. 2010 Apr;27(2):166-70.
https://academic.oup.com/fampra/article/27/2/166/510395
http://www.ncbi.nlm.nih.gov/pubmed/20026553?tool=bestpractice.com
Transient synovitis is extremely uncommon in adults.[5]Quintos-Macasa AM, Serebro L, Menon Y. Transient synovitis of the hip in an adult. South Med J. 2006 Feb;99(2):184-5.
http://www.ncbi.nlm.nih.gov/pubmed/16509560?tool=bestpractice.com
It tends to occur more in the autumn and winter months. It is about twice as common in boys compared with girls and uncommon among black children.[6]Vijlbrief AS, Bruijnzeels MA, van der Wouden JC, et al. Incidence and management of transient synovitis of the hip: a study in Dutch general practice. Br J Gen Pract. 1992 Oct;42(363):426-8.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1372234
http://www.ncbi.nlm.nih.gov/pubmed/1466922?tool=bestpractice.com
It is rarely bilateral. Recurrent episodes occur in 4% to 17% of children. Those who do have a recurrent episode usually have a benign course, although in about 10% it may be the presenting feature of a chronic inflammatory condition.[7]Uziel Y, Butbul-Aviel Y, Barash J, et al. Recurrent transient synovitis of the hip in childhood. Long-term outcome among 39 patients. J Rheumatol. 2006 Apr;33(4):810-1.
http://www.ncbi.nlm.nih.gov/pubmed/16583482?tool=bestpractice.com