The Functional Toll of Scheuermann Kyphosis

Abstract

Background:

Scheuermann kyphosis (SK) is a structural kyphotic deformity that typically emerges in adolescence, characterized by vertebral wedging of >5° in at least three vertebrae. Although surgical management is standard for severe curvature, treatment increasingly prioritizes functional outcomes and pain reduction as key measures of surgical success. Despite the importance of these clinical markers for surgical outcomes, little is known about the extent of functional limitations SK imposes across age groups.

Methods:

We analyzed data from 168 patients in the Scheuermann's Disease Fund CoRDS registry from September 2021 to March 2025. Participants completed a 196-item questionnaire covering demographics, age of diagnosis, pain severity, daily activity ability, and disability benefits. Data cleaning and statistical analyses, including descriptive and two-tailed chi-square tests (α = 0.05), were conducted with IBM SPSS Statistics v30.

Results:

Patients diagnosed with SK were frequently between the ages of 0 to 20 (59.5%), 21-40 (28.0%), and >40 (12.5%) years, with 63.1% reporting severe pain. Among patients with severe pain, most report neuropathy (92.2%), fatigue (95.1%), pain while walking (94.2%), pain while standing (96.2%), pain while sitting (95.3%), difficulty with performing daily activities (98.0%), no longer performed hobbies (97.0%), and needed assistance from others to perform daily activities (51.5%). In particular, patients diagnosed with SK between the ages of 21 to 40 years were more likely to experience severe pain (78.7%, P = 0.002), pain while standing (100.0% P = 0.004), and pain while sitting (97.8%, P = 0.009).

Conclusion:

SK leads to progressive and often debilitating functional decline, with adults in this cohort diagnosed between 21 to 40 years experiencing the most severe pain and highest rates of limitations in sitting, standing, and walking. These findings underscore the need for early detection and proactive functional rehabilitation in this population.

Scheuermann kyphosis (SK) is a structural hyperkyphosis defined by anterior wedging of at least 5° in three or more consecutive vertebrae.^1,2 It predominantly affects adolescent males, with a prevalence ranging from 0.4% to 8%, and most commonly involves the thoracic spine.^2,3 Clinical symptoms often include axial pain, postural imbalance, fatigue, and reduced spinal mobility.^4-6 Standard management strategies prioritize conservative interventions, including bracing treatment and physical therapy, particularly in skeletally immature patients.⁷ Surgical correction is generally reserved for patients with progressive deformity exceeding a Cobb angle of 75° or those with non-relieved pain from nonsurgical treatment.⁷

Functional impairment is well-documented across other spinal deformity populations, including adolescent idiopathic scoliosis (AIS), adult spinal deformity (ASD), and fixed kyphotic syndromes.^8-11 In AIS, pain and activity limitations are frequently reported, despite relatively modest curve magnitudes.⁹ In ASD, sagittal imbalance and compensatory mechanisms, such as increased pelvic retroversion and lumbar hypolordosis, have been closely linked to functional impairment and poor health-related quality of life.^12,13 These findings suggest that radiographic measures alone may inadequately capture the clinical burden of deformity. As in these cohorts, pain and disability in kyphotic conditions often reflect biomechanical disruption and compensatory exhaustion rather than curve magnitude alone.¹⁴

Although the radiographic features and surgical correction of SK have been well characterized,^15,16 existing literature remains limited in scope regarding functional outcomes, particularly in adults worldwide. Large-scale, patient-reported outcomes data remain scarce, and few studies have investigated the real-world impact of kyphosis progression in this cohort. Given that sagittal plane deformities can compromise spinal mechanics and functional capacity before meeting surgical criteria,¹² current clinical pathways may therefore fail to identify patients experiencing functional decline in the absence of overt structural progression. This study uses data from the CoRDS registry to evaluate pain severity, functional limitations, and disability burden across a global cohort of patients with SK. Our findings are stratified by age at diagnosis, Cobb angle, and self-reported pain severity to identify clinically relevant trends in symptom progression and activity restriction.

Methods

Study Design

This study was a retrospective analysis of prospectively collected, patient-reported data from the Scheuermann's Disease Fund registry, maintained by the Coordination of Rare Diseases at Sanford (CoRDS; https://research.sanfordhealth.org/rare-disease-registry). Individuals with self-reported SK filled out a 196-item survey about their functional and disability status. The questionnaire contained demographics (age of onset, current age, sex), clinical characteristics (Cobb angle category and kyphotic apex location), pain (experienced during activities, severity, and neuropathy), and functional limitations (performing daily activities, needing assistance, performing hobbies, and disability status). Select questions from the CoRDS survey are presented in Supplementary Table 1, https://links.lww.com/JG9/A570. Institutional review board approval was waived since the data set was deidentified for research use, and electronic informed consent was obtained from all patients included in the database.

Registry Enrollment and Data Acquisition

Participants were identified through the Scheuermann's Disease Fund registry, a disease-specific registry hosted within the CoRDS, an international online platform designed to facilitate research participation among individuals with rare diseases. Individuals with a self-reported diagnosis of SK voluntarily self-enroll through the CoRDS website and complete a comprehensive registry questionnaire after providing electronic informed consent for research participation. The Scheuermann's Disease Fund registry includes a 196-item survey that collects patient-reported demographic information, clinical characteristics (including age at diagnosis, Cobb angle category, and kyphotic apex location when known), pain severity, functional limitations, disability status, and psychosocial variables. For this study, deidentified registry data were requested from CoRDS administrators and included all participants enrolled between September 2021 and March 2025. A total of 168 respondents were included in the analytic cohort. Because participation is voluntary and data are self-reported, not all variables were available for all participants; data availability therefore varied across measures including Cobb angle, kyphotic apex location, and mental health variables. All data provided to the study investigators were fully deidentified before release. Institutional review board approval was waived due to the use of deidentified registry data, and all participants had previously provided electronic consent for research use of their information through the CoRDS platform.

Statistical Analysis

The complete data set was obtained from CoRDS. Participant characteristics were described using frequencies and percentages. Associations between functional limitations and categorical predictors (age group at diagnosis, pain severity, and curvature) were evaluated using chi-square analyses. In addition, cohorts were stratified by age at diagnosis (0 to 20 years, 21 to 40 years, ≥41 years), pain severity (mild, moderate, severe), and Cobb angle (≤60°, 61 to 80°, ≥81°). Multivariable logistic regression analyses were done to evaluate independent predictors of functional impairment, including disability, need for assistance with daily activities, difficulty performing daily activities, and walking limitation. Models were adjusted for age at diagnosis, Cobb angle category, pain category, extreme fatigue, and neuropathy, with listwise sample sizes ranging from 88 to 96 participants. All statistical analyses were conducted using IBM SPSS Statistics version 30, with a significance threshold set at P < 0.05.

Results

Patient Demographics

A total of 168 individuals diagnosed with SK were included in the study. Most individuals were diagnosed between 0 and 20 years of age (59.5%), followed by 21 to 40 years (28.0%), and older than 40 years (12.5%). Regarding pain severity, the majority reported severe pain (63.1%), with moderate (29.2%) and mild (7.7%) pain reported less frequently. The distribution of Cobb angles among the 106 individuals with available data showed that 44.3% had angles greater than 80°, 40.6% had angles between 60° and 80°, and 15.1% had angles less than 60°. Of the 89 individuals with recorded kyphotic apex locations, the apex was most commonly located in the thoracic spine (89.9%), followed by the lumbar (7.9%) and cervical (2.2%) regions. Of the 158 participants who responded to the corrective surgery item, 62 (39.2%) reported having undergone corrective surgery for SK, whereas 96 (60.8%) had not (Table 1).

Table 1.

Demographics and Radiographic Characteristics

Variable	N (%)
Age at diagnosis (n = 168)
0 to 20 years	100 (59.5)
21 to 40 years	47 (28.0)
>40 years	21 (12.5)
Pain severity (n = 168)
Mild	13 (7.7)
Moderate	49 (29.2)
Severe	106 (63.1)
Cobb angles (n = 106)
<60°	16 (15.1)
60–80°	43 (40.6)
>80°	47 (44.3)
Kyphotic apex location (n = 89)
Cervical (C1-C7)	2 (2.2)
Thoracic (T1-T12)	80 (89.9)
Lumbar (L1-L5)	7 (7.9)
Corrective surgery (n = 158)
No	96 (60.8)
Yes	62 (39.2)

Functional Limitations and Pain Characteristics by Age at Diagnosis

Pain severity differed markedly across age groups (P = 0.002), with severe pain most frequently reported among individuals diagnosed between 21 and 40 years (78.7%) compared with 60.0% and 47.6% in the younger-age and older-age groups, respectively. Difficulty walking more than one mile was common across all age groups, but those diagnosed at 21 to 40 years showed the highest proportion unable to walk (29.8%, P = 0.037). Standing pain (P = 0.004) and sitting pain (P = 0.009) were also markedly more prevalent in individuals diagnosed between 21 to 40 years, as were neuropathy (P = 0.028) and fatigue (P < 0.001). Functional limitations such as difficulty performing daily activities (P = 0.043), need for assistance (P = 0.038), and disability (P = 0.038) were also markedly more frequent in this group (Table 2).

Table 2.

Functional Limitations and Pain Characteristics by Age at Diagnosis Among Individuals With Scheuermann Kyphosis

Variable	0–20 years	21–40 years	41+ years	P
Pain severitya				0.002
Mild	13 (13.0)	0 (0.0)	0 (0.0)
Moderate	27 (27.0)	19 (21.3)	11 (52.4)
Severe	60 (60.0)	37 (78.7)	10 (47.6)
Pain walkingb				0.045
Cannot walk	17 (18.9)	14 (29.8)	2 (9.5)
<1 mile walk	38 (42.2)	11 (23.4)	5 (23.8)
>1 mile walk	35 (38.9)	22 (46.8)	14 (66.7)
Pain standingc	82 (83.7)	47 (100.0)	18 (85.7)	0.004
Pain sittingd	80 (82.5)	45 (97.8)	16 (76.2)	0.009
Neuropathye	77 (81.1)	41 (93.2)	18 (100.0)	0.028
Fatiguef	71 (74.7)	43 (97.7)	14 (70.0)	<0.001
Difficulty performing daily activitiesg	75 (78.1)	40 (90.9)	13 (65.0)	0.043
Need assistance for activitiesh	29 (29.9)	23 (52.3)	7 (35.0)	0.038
Disabledi	26 (28.0)	19 (45.2)	2 (13.3)	0.038

^an = 168.

^bn = 158.

^cn = 166.

^dn = 164.

^en = 157.

^fn = 159.

^gn = 118.

^hn = 150.

ⁱn = 150.

Stratification by Pain Severity

Severe pain was associated with higher prevalence of walking limitations (94.2%, P < 0.001), including inability to walk (28.8%) and any walking distance (<1 mile, 38.5%; >1 mile, 32.7%). Notable differences were observed in pain while standing (P < 0.001), with 20.6% of those unable to stand with severe pain and 63.7% standing for less than 30 minutes with severe pain (P = 0.002). Similarly, pain while sitting was more frequent and severe in this group (P < 0.001), with 50.0% reporting sitting tolerance under 30 minutes and severe pain. Neuropathy (P < 0.001), fatigue (P < 0.001), and difficulty performing daily activities (P < 0.001) were markedly more common among individuals with severe pain. These individuals also more frequently reported discontinuing hobbies (P < 0.001), needing assistance (P < 0.001), and being disabled (P < 0.001) (Table 3).

Table 3.

Functional Limitations and Pain Characteristics by Pain Severity Among Individuals With Scheuermann Kyphosis

Variable	Mild	Moderate	Severe	P
Pain walkinga	2 (15.4)	30 (63.8)	98 (94.2)	<0.001
Cannot walk	0 (0.0)	3 (6.7)	30 (28.8)	<0.001
<1 mile walk	1 (10.0)	13 (28.9)	40 (38.5)
>1 mile walk	9 (90.0)	29 (64.4)	34 (32.7)
Pain standingb	4 (30.8)	41 (85.4)	102 (96.2)	<0.001
Unable to stand	0 (0.0)	4 (9.8)	21 (20.6)	0.002
<30 mins stand	2 (50.0)	18 (43.9)	65 (63.7)
>30 mins stand	2 (50.0)	19 (46.3)	16 (15.7)
Pain sittingc	3 (25.0)	38 (80.9)	101 (95.3)	<0.001
Cannot sit	0 (0.0)	3 (7.9)	12 (12.0)	0.036
<30 mins sit	1 (33.3)	10 (26.3)	50 (50.0)
>30 mins sit	2 (67.7)	25 (65.8)	38 (38.0)
Neuropathyd	4 (33.3)	38 (86.4)	94 (92.2)	<0.001
Upper extremities	1 (25.0)	25 (69.4)	72 (80.9)	0.024
Lower extremities	3 (75.0)	22 (61.1)	77 (85.6)	0.010
Fatiguee	2 (16.7)	28 (62.2)	98 (95.1)	<0.001
Difficulty performing daily activitiesf	2 (18.2)	27 (56.3)	100 (98.0)	<0.001
No longer perform hobbiesg	4 (33.3)	32 (68.1)	97 (97.0)	<0.001
Need assistance for activitiesh	0 (0.0)	7 (14.6)	52 (51.5)	<0.001
Disabledi	0 (0.0)	1 (2.5)	46 (46.5)	<0.001

^an = 164.

^bn = 167.

^cn = 165.

^dn = 158.

^en = 160.

^fn = 161.

^gn = 159.

^hn = 162.

ⁱn = 151.

Stratification by Cobb Angle

Pain severity differed markedly by Cobb angle group (P = 0.008), with individuals in the >81° group less frequently reporting severe pain (48.9%) compared with those in the 40 to 60° (75.0%) group. However, no statistically significant differences were observed among the Cobb angle groups for walking ability (P = 0.770), standing (P = 0.889), sitting (P = 0.962), neuropathy (P = 0.717), fatigue (P = 0.253), or difficulty with daily activities (P = 0.989). Similarly, rates of needing assistance (P = 0.761) and disability (P = 0.776) did not differ markedly among the curvature groups (Table 4).

Table 4.

Functional Limitations and Pain Characteristics by Curvature Severity Among Individuals With Scheuermann Kyphosis

Variable	40-60° Cobb	61–80° Cobb	> 81° Cobb	P
Pain severitya				0.008
Mild	2 (12.5)	5 (11.6)	2 (4.3)
Moderate	2 (12.5)	7 (16.3)	22 (46.8)
Severe	12 (75.0)	31 (72.1)	23 (48.9)
Pain walkingb	12 (75.0)	35 (83.3)	38 (80.9)	0.770
Pain standingc	14 (87.5)	36 (85.7)	41 (89.1)	0.889
Pain sittingd	13 (86.7)	36 (87.8)	41 (89.1)	0.962
Neuropathye	14 (87.5)	33 (84.6)	35 (79.5)	0.717
Fatiguef	14 (93.3)	32 (80.0)	33 (73.3)	0.253
Difficulty performing daily activitiesg	12 (80.0)	30 (78.9)	36 (78.3)	0.989
Need assistance for activitiesh	5 (33.3)	10 (25.0)	14 (31.1)	0.761
Disabledi	3 (20.0)	10 (28.6)	10 (23.3)	0.776

^an = 106.

^bn = 105.

^cn = 104.

^dn = 102.

^en = 99.

^fn = 100.

^gn = 99.

^hn = 100.

ⁱn = 93.

Multivariate Analysis

Across models, pain category remained the most consistent independent predictor of functional impairment. Higher pain severity was markedly associated with greater odds of disability (OR 3.14, 95% CI, 1.31 to 7.53, P = 0.010), need for assistance with daily activities (OR 4.88, 95% CI, 2.01 to 11.89, P < 0.001), difficulty performing daily activities (OR 21.61, 95% CI, 3.90 to 119.7, P < 0.001), and walking limitation (OR 4.21, 95% CI, 1.49 to 11.88, P = 0.007). Extreme fatigue was additionally associated with difficulty performing daily activities (OR 6.30, 95% CI, 1.00 to 39.60, P = 0.050). Neuropathy was inversely associated with disability (OR 0.03, 95% CI, 0.003 to 0.20, P < 0.001), although this finding should be interpreted cautiously given evidence of model separation. Age at diagnosis and Cobb angle category were not markedly associated with any functional outcome after adjustment.

Discussion

This study highlights the substantial burden of pain and functional impairment experienced by individuals with SK, particularly among those diagnosed during adolescence. The data demonstrate that functional limitations are both early and profound, often manifesting well before individuals meet radiographic thresholds typically used to guide clinical decision making.^17,18 Although curve severity and pain both correlate with impairment, this study suggests that radiographic classification alone may underestimate the lived disability experienced by these patients.

A notable finding was the elevated burden of symptoms and functional limitations among those diagnosed between the age of 21 and 40 years. This group reported markedly higher rates of severe pain, limited mobility, neuropathy, and fatigue compared with those diagnosed earlier or later in life. These findings may reflect a population experiencing meaningful functional impairment before entering traditional surgical decision pathways.^19,20 Current orthopaedic workflows may overlook patients who are perceived as low-risk based solely on curve progression, despite their high functional burden.⁷ The data also suggest that functional impairment in these patients may occur independently of curve magnitude, challenging the assumption that pediatric-onset disease with smaller curves is clinically benign.^21-24 The greater functional burden observed among individuals diagnosed during early adulthood should not be interpreted as evidence that early diagnosis worsens outcomes. Rather, age at diagnosis in this registry likely reflects differences in disease trajectory and cumulative duration of symptoms. Individuals diagnosed earlier may have experienced longer exposure to structural deformity. These findings therefore highlight the importance of understanding how SK evolves across the lifespan and whether treatment strategies and functional support should differ between adolescents and adults.

Pain severity emerged as another predictor of disability, demonstrating a stronger association with functional limitation than curve magnitude. Individuals with severe pain reported markedly higher rates of walking intolerance, limitations in sitting and standing, fatigue, and dependency on assistance. These findings reinforce the importance of incorporating patient-reported outcomes into clinical assessment, particularly given the limitations of radiographic markers in capturing functional status.^24-26 Although previous studies have emphasized curvature thresholds for surgical decision making, this study supports the growing recognition that subjective pain and functional metrics are critical in understanding disease burden and guiding treatment planning.²⁷

Importantly, this study also identifies a disconnect between radiographic classification and real-world disability. Cobb angle severity was not markedly associated with most functional outcomes, aside from pain severity. Although it is plausible that more severe curvatures contribute to pain, the nonnegligible differences in daily activity limitations, fatigue, and disability across Cobb angle groups suggest that other factors, such as age at diagnosis and pain intensity, may play a more direct role in driving functional loss. In addition, the lack of strong correlation between curvature and function aligns with prior evidence suggesting that psychosocial and developmental factors, especially during adolescence, may amplify the functional consequences of pain and spinal deformity.²⁸ These findings underscore the need for a broader understanding of disease trajectories that includes the developmental context of diagnosis and progression.

The lack of a strong association between Cobb angle severity and most functional outcomes in this cohort may also reflect heterogeneity in disease presentation rather than solely measurement limitations. Some individuals with larger curvatures may develop biomechanical adaptations that allow preservation of function, whereas others with more moderate deformities may experience disproportionate pain and activity limitation. This pattern raises the possibility of distinct clinical phenotypes, including structural deformity-dominant and pain-dominant presentations of SK. Although this study was not designed to evaluate these mechanisms directly, these findings suggest that functional burden may not be fully captured by radiographic malalignment alone and highlight the need for future studies examining biomechanical adaptation, pain processing, and patient-reported outcomes across different disease trajectories.

This study has several limitations. All data were self-reported, including diagnosis, curvature severity, and functional outcomes, without radiographic verification. As such, misclassification is possible. In addition, because participation in the registry is voluntary and facilitated through a patient advocacy network, the cohort may overrepresent individuals with greater symptom burden or healthcare engagement. Therefore, the findings should be interpreted as reflecting functional experiences among registry participants rather than the full population of individuals with SK. Because registry participation and survey completion were voluntary, some variables—including Cobb angle and kyphotic apex location—were missing for a proportion of participants. Analyses were therefore done using available-case data, which may introduce bias if missingness is not random. Furthermore, multiple exploratory comparisons were conducted across functional outcomes, increasing the possibility of Type I error; accordingly, these results should be interpreted as hypothesis generating rather than definitive causal associations. Although the registry includes international participants, patient-level country-of-origin data were not available in the deidentified data set, precluding analysis of geographic differences in disability reporting or access to care. Finally, responses may be subject to recall bias, particularly for retrospective pain assessments. The registry questionnaire was designed to capture patient-reported experiences and symptom burden rather than function as a formally validated psychometric instrument. Future studies incorporating objective clinical assessments and longitudinal follow-up will be necessary to better characterize disease progression and treatment responsiveness.

Conclusion

Individuals with SK experience substantial pain and functional impairment, particularly those diagnosed between 21 and 40 years and those with higher pain severity. Despite this burden, many patients are not diagnosed early, are rarely referred for rehabilitation and are often not recognized within disability systems. These findings highlight the need to expand clinical care beyond radiographic assessment by incorporating functional evaluations, identifying pain-disability trajectories, and extending support to nonsurgical and younger-diagnosed patients to improve outcomes and quality of life.

Supplementary Material

jagrr-10-e25.00281-s001.docx ^{(14.7KB, docx)}