Childhood Myositis Assessment Scale (CMAS)

CMAS score evaluates severity of muscle involvement in children with idiopathic inflammatory myopathies, in terms of strength and endurance.

Refer to the text below the scale for more information on it’s usage, validity, strengths and limitations.

CMAS is a quantitative instrument used to evaluate the severity of muscle involvement in children with idiopathic inflammatory myopathies. It assesses muscle function, specifically in terms of strength and endurance, across a broad spectrum of capabilities in pediatric patients of various ages.

CMAS scores vary from 0 to 52, where a score of 52 indicates normal or nearly normal strength, function, and/or endurance. There are no validated cut-points established yet.

However, through a consensus process, scores below 15 have been agreed upon to signify severe disease.

In a study by Huber et al., CMAS values were compared to CHAQ scores. Scores representing no, mild, mild-to-moderate, and moderate impairment were identified as 48, 45, 39, and 30, respectively.


Head elevation (neck flexion)

No. of seconds (optional)

Leg raise/touch object


Head elevation (neck flexion)

No. of seconds (optional)

Supine to prone



5.1 Hands on thighs, with counterbalance
5.2 Hands across chest, with counterbalance
5.3 Hands behind head, with counterbalance
5.4 Hands on thighs, without counterbalance
5.5 Hands across chest, without counterbalance
5.6 Hands behind head, without counterbalance

Supine to sit


Arm raise/straighten


Head elevation (neck flexion)

No. of seconds (optional)

Floor sit

Going from a standing position to a sitting position on the floor.

All-fours maneuver


Floor rise

Going from a kneeling position on the floor to a standing position.

Chair rise


Stool step


Pick up

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Childhood Myositis Assessment Scale explained

CMAS is a quantitative tool for assessing the severity of muscle involvement in children with idiopathic inflammatory myopathies. It observes muscle function in the areas of strength and endurance across a wide range of ability in patients of different ages. The above scale reproduces the original study scale as the tool has not been revised nor updated since its publishing in 1999.

It consists of 14 ordinal items purposefully weighted towards lower extremity proximal and axial muscle groups more than upper extremity and distal muscle groups to reflect the pattern of weakness in juvenile myositis.

Each item has specific scoring options, highlighting whether an activity can be performed or not, and with what degree of difficulty, if any. The endurance items are categorized into ordinal scale scores. All activities must be performed at the time that the scale is administered by a trained therapist or clinician. Access to a step stool and chairs of appropriate height is required, as well as a watch and floor mat for comfort.

CMAS scores range from 0 to 52, with 52 representing normal or near normal strength, function and/or endurance.

Validated cut-points have not been established. However, as part of a consensus process, it was agreed that values

Huber et al. used a process that compared CMAS values to CHAQ scores, values corresponding to no, mild, mild-to-moderate, and moderate impairment were 48, 45, 39, and 30, respectively.

Missing data may be common in the administration of the scale for patients under 5 years of age due to limited ability to cooperate. Inability to complete a task should be scored as 0.

In children with juvenile idiopathic inflammatory myopathies, the CMAS correlated highly with the CHAQ and total MMT score (Spearman r = −0.73 and 0.73, respectively, P < 0.0001) and moderately with physician global disease activity, physician skin activity, and parent disease severity, as well as serum creatine kinase, and prednisone dose (Spearmanor Pearson r = −0.44 to −0.61, P < 0.0001).

Correlations with MRI muscle edema and damage were moderate (Spearman r = −0.48 to −0.57), and correlations with serum levels of enzymes were low but often significant (Spearman r = −0.11 to −0.36).

A group of adult and pediatric rheumatologists and neurologists have reached consensus that measures of physical function should improve by ≥ 15% to classify a patient as improved.

The CMAS has proven excellent reliability, construct validity, and responsiveness in juvenile myositis for pediatric patients ages 4 – 18 years. But has been criticised for taking too much time too administer, being difficult to assess in younger children and showing poor sensitivity and specificity as a measure of activity for patients with moderate to severe damage, including patients who have muscle atrophy and fixed joint contractures.

The CMAS has been included as a core set activity measure by both IMACS and PRINTO for juvenile myositis.


About the original study

In the 1999 study by Lovell et al. the scale was developed then a training video and written instructions were developed and reviewed by the physicians participating in this study. Via a randomized block design, 12 physicians independently scored 10 children (9 with dermatomyositis, 1 with polymyositis; ages 4-15 years) twice in one day (morning and afternoon) on the CMAS.

A pediatric physical therapist performed quantitative manual muscle strength testing (MMT) twice on each child (morning and afternoon), including the neck, trunk, and proximal and distal extremity muscle groups.

The total CMAS scores correlated with the physician's global assessment (by visual analog scale) of disease activity, the MMT score, serum creatine kinase level, and the Juvenile Arthritis Functional Assessment Report score.

Possible results are on a scale from 0 to 52, where the higher the score, the greater the observed muscle strength and endurance.

Interrater reliability (Kendall's coefficient of concordance) ranged from 0.77 to 1.0 for individual items (all P < 0.001), and overall, it was 0.95 (P < 0.001).

Intrarater reliability for the individual physicians was measured by correlation of the CMAS scores for each patient on 2 separate evaluations and ranged from 0.97 to 0.99, with an overall correlation for all physicians of 0.98 (all P < 0.001).

The CMAS is validated to assess muscle function (domains of strength and endurance) in pediatric patients with idiopathic inflammatory myopathies and has been used in both therapeutic trials and routine clinical care.



Original reference

Lovell DJ, Lindsley CB, Rennebohm RM, Ballinger SH, Bowyer SL, Giannini EH, Hicks JE, Levinson JE, Mier R, Pachman LM, Passo MH, Perez MD, Reed AM, Schikler KN, Smith M, Zemel LS, Rider LG. Development of validated disease activity and damage indices for the juvenile idiopathic inflammatory myopathies. II. The Childhood Myositis Assessment Scale (CMAS): a quantitative tool for the evaluation of muscle function. The Juvenile Dermatomyositis Disease Activity Collaborative Study Group. Arthritis Rheum. 1999; 42(10):2213-9.


Huber AM, Feldman BM, Rennebohm RM, Hicks JE, Lindsley CB, Perez MD, Zemel LS, Wallace CA, Ballinger SH, Passo MH, Reed AM, Summers RM, White PH, Katona IM, Miller FW, Lachenbruch PA, Rider LG; Juvenile Dermatomyositis Disease Activity Collaborative Study Group. Validation and clinical significance of the Childhood Myositis Assessment Scale for assessment of muscle function in the juvenile idiopathic inflammatory myopathies. Arthritis Rheum. 2004; 50(5):1595-603.

Other references

Miller FW, Rider LG, Chung YL, Cooper R, Danko K, Farewell V, et al. Proposed preliminary core set measures for disease outcome assessment in adult and juvenile idiopathic inflammatory myopathies. Rheumatology. 2001; 40(11):1262–73.

Ruperto N, Ravelli A, Pistorio A, Ferriani V, Calvo I, Ganser G, et al. The provisional Paediatric Rheumatology International Trials Organisation/American College of Rheumatology/European League Against Rheumatism Disease activity core set for the evaluation of response to therapy in juvenile dermatomyositis: a prospective validation study. Arthritis Rheum. 2008; 59(1):4–13.

Ruperto N, Pistorio A, Ravelli A, Rider LG, Pilkington C, Oliveira S, et al. The Paediatric Rheumatology International Trials Organisation provisional criteria for the evaluation of response to therapy in juvenile dermatomyositis. Arthritis Care Res (Hoboken) 2010; 62(11):1533–41.

Huber AM, Giannini EH, Bowyer SL, Kim S, Lang B, Lindsley CB, et al. Protocols for the initial treatment of moderately severe juvenile dermatomyositis: results of a Children’s Arthritis and Rheumatology Research Alliance Consensus Conference. Arthritis Care Res (Hoboken) 2010; 62(2):219–25.

Specialty: Pediatrics

Objective: Stratification

No. Of Criteria: 14

Year Of Study: 1999

Abbreviation: CMAS

Article By: Denise Nedea

Published On: April 18, 2024

Last Checked: April 18, 2024

Next Review: April 18, 2029