Background: Paediatric chronic lower limb pain is common, and often distressing and disabling for children and adolescents. Recently, the classification of chronic pain conditions changed within the International Classification of Diseases 11 (ICD-11)[1]. One significant new inclusion is ‘chronic primary musculoskeletal pain’. This is the diagnosis given for chronic pain in the muscles, bones, joints, or tendons associated with significant emotional distress and/or functional disability, but which cannot be better accounted for by another condition[2]. There are many conditions and diagnoses known to result in chronic lower limb pain in children, some of which describe similar or overlapping clinical presentations. Some of these existing terminologies may be able to be better described within the new classification system, or be considered under these broad parent terms for the purpose of future research.

Objectives: To categorise chronic lower limb pain conditions in children as chronic primary or secondary musculoskeletal pain based on expert consensus.

Methods: An international panel of experts in paediatric lower limb pain were invited to participate in a three round online Delphi survey. Participants were presented with a list of 124 conditions known to result in chronic lower limb pain in children and adolescents, sourced from a recent scoping review. Participants were asked to select whether they believed each condition could be categorised as either chronic primary or chronic secondary musculoskeletal pain, or to abstain, based on the International Association for the Study of Pain (IASP) descriptions. Conditions achieving >70% agreement were deemed to have reached consensus for categorisation, while conditions achieving 50-69% agreement were taken to the following round to be re-rated. Conditions achieving <50% agreement were excluded from future rounds. Participants were given the opportunity after Round 1 to suggest additional conditions which were not present in the initial list, of which seven were included in Round 2.

Results: There were 21 medical and allied health professionals from eight countries who participated. Four conditions were categorised as chronic primary musculoskeletal pain across three founds. These were ‘growing pains’, ‘musculoskeletal pain’ (a banner term including ‘regional fibromyalgia’, ‘chronic musculoskeletal pain’, ‘idiopathic pain’), ‘persistent lower limb pain in the presence of restless leg syndrome’, and ‘persistent lower limb pain in the presence of functional neurological disorder’. There were 117 conditions categorised as chronic secondary musculoskeletal pain. Nine conditions were uncategorised due to not reaching 50% agreement in Round 1 or 2, while only one condition did not reach consensus or agreement over all three rounds – ‘persistent lower limb pain in the presence of generalised joint hypermobility’.

Conclusion: Experts categorised four paediatric lower limb pain conditions as chronic primary musculoskeletal pain through this Delphi panel. These share features of resulting in chronic pain without a clear underlying pathophysiological process, or historically being diagnoses of exclusion. By considering these conditions under the umbrella of ‘chronic primary musculoskeletal pain’, there is opportunity for further development of combined clinical guidance and a reduction in unnecessary variation in care to address chronic pain.

REFERENCES: [1] Treede RD, Rief W, Barke A, Aziz Q, Bennett MI, Benoliel R, Cohen M, Evers S, Finnerup NB, First MB, Giamberardino MA, Kaasa S, Kosek E, Lavand’homme P, Nicholas M, Perrot S, Scholz J, Schug S, Smith BH, Svensson P, Vlaeyen JWS, Wang SJ. A classification of chronic pain for ICD-11. Pain. 2015 Jun;156(6):1003-1007. doi: 10.1097/j.pain.0000000000000160.

[2] Nicholas, M., Vlaeyen, J. W. S., Rief, W., Barke, A., Aziz, Q., Benoliel, R., Cohen, M., Evers, S., Giamberardino, M. A., Goebel, A., Korwisi, B., Perrot, S., Svensson, P., Wang, S.-J., Treede, R.-D., & Pain, T. I. T. f. t. C. o. C. (2019). The IASP classification of chronic pain for ICD-11: chronic primary pain. PAIN , 160 (1), 28-37. https://doi.org/10.1097/j.pain.0000000000001390 .

Acknowledgements: NIL.

Disclosure of Interests: None declared.