M66.81 Spontaneous rupture of other tendons, shoulder

ICD-10-CM Diagnosis Code M66.81: Spontaneous rupture of other tendons, shoulder

ICD-10-CM code M66.81 identifies a spontaneous rupture of other shoulder tendons. It is an active diagnosis under the parent category M66.8. General clinical literature links spontaneous tendon ruptures to underlying deterioration and specific risk factors, while billing articles list related laterality codes. 1 2 3

Plain-language overview

Code M66.81 represents a pathologic function designated as a spontaneous rupture of other tendons located in the shoulder, serving as an active terminology record for diagnosis tracking. 1

What this code represents

The diagnosis code M66.81 holds no narrower child concepts within the ICD-10-CM terminology and directly descends from the parent concept M66.8, spontaneous rupture of other tendons. 1

Coding details

The M66.81 category is listed alongside more specific codes, including M66.811, M66.812, and M66.819, within an ICD-10-CM code group document for shoulder tendon ruptures. 4

A Medicare article lists M66.811 for a spontaneous rupture of other tendons in the right shoulder and M66.812 for the left shoulder, alongside transient synovitis codes. 3

Clinical context

Clinical literature indicates that deteriorated tendons face an increased risk of rupture, and upper body tendons like the subscapularis or spinatus can experience spontaneous rupture. 2

Spontaneous tendon ruptures have been observed in patients with pre-existing tendinopathy, rheumatoid arthritis, or after starting oral corticosteroid therapy, sometimes requiring surgical treatment. 2

Documentation considerations

The cited sources list distinct right shoulder, left shoulder, and unspecified shoulder codes under the M66.81 category for spontaneous rupture of other shoulder tendons. 3 4

What the sources add

While terminology records define the M66.81 diagnosis hierarchy, Medicare billing articles list operational laterality codes, and clinical reviews detail the systemic risk factors for spontaneous ruptures. 1 2 3

Sources

1. ICD-10-CM M66.81 terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Cephalexin-associated Achilles Tendonitis: Case Report and Review of Drug-induced Tendinopathy — pmc.ncbi.nlm.nih.gov; accessed 2026-07-27.
3. Article - Billing and Coding: Pain Management - injection of tendon sheaths, ligaments, ganglion cysts, carpal and tarsal tunnels (A52863) — cms.gov; accessed 2026-07-27.
4. Multimedia Appendix 1: ICD-10-CM Code Groups for ... — medrxiv.org; accessed 2026-07-27.