Prior to the use of disease-modifying therapies (DMTs), hip pain most commonly occurred in patients with spinal muscular atrophy (SMA) type 2 disease compared to those with SMA type 1, according to a retrospective study published in JB & JS Open Access.

In the study, 23 out of the 72 patients (32%) in the cohort of nonambulatory children with either SMA type 1 or type 2 reported hip pain during the clinical course of the disease. The pain was more commonly reported in patients with SMA type 2 (49%) compared to those with type 1 (12%; P =0.001).

In contrast, all patients with type 1 SMA and all but 1 (97%) of the patients with type 2 had abnormal findings on hip radiographs at the onset of pain or the last follow-up. Hip status was not significantly different between patients who reported pain and those who did not. Also, no difference was observed between those with mild or no pain and those reporting severe pain.

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“This study is, to our knowledge, the largest investigation to date to assess hip pain among nonambulatory children with type 1 or type 2 SMA and suggests that symptoms rather than radiographs be utilized to direct care,” the authors wrote.

Most patients who reported pain were managed with over-the-counter medications, positioning changes, durable medical equipment changes, or observation. However, 7 patients with type 2 SMA had pain severe enough to undergo invasive procedures, including intra-articular injections (n=6), spinal implant revision (n=2), and proximal femoral resection (n=1). Pain was reduced in most patients but only eliminated in 1 patient.

Hip pain also appeared to be more likely in patients with type 2 with higher copies of the survival motor neuron 2 gene, with 17% of those with 2 copies, 53% of those with 3 copies, and 50% of those with 4 copies reporting pain.

A total of 72 patients with SMA were recruited for the retrospective study, including 33 with type 1 disease and 39 with type 2. The participants were primarily females (n=44). The mean age at onset of hip pain was 8 years for SMA type 1 patients and 9 years for the SMA type 2 group.

“This study offers baseline data for hip pathology and pain as the medical treatment of SMA transitions to DMTs,” the authors noted.


Hanna RB, Nahm N, Bent MA, et al. Hip pain in nonambulatory children with type I or II spinal muscular atrophy. JB JS Open Access. 2022;7(3). doi:10.2106/JBJS.OA.22.00011