M61.129Myositis ossificans progressiva, unspecified upper arm

M61.129 is the ICD-10-CM diagnosis code for myositis ossificans progressiva, unspecified upper arm. It belongs to category M61 (calcification and ossification of muscle), block M60-M63 (disorders of muscles) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within M61.12, choose M61.129 (unspecified upper arm) only when documentation doesn't support a more specific option: right upper arm (M61.121) and left upper arm (M61.122).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 557 (Tendonitis, Myositis and Bursitis with MCC, relative weight 1.489) and DRG 558 (Tendonitis, Myositis and Bursitis without MCC, relative weight 0.8875), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015, and changed in FY2026 (title revised).

Before ICD-10, this condition was coded in ICD-9-CM as 728.11 (progressive myositis ossificans).