M65.819 Other synovitis and tenosynovitis, unspecified shoulder

ICD-10-CM Diagnosis Code M65.819: Other Synovitis and Tenosynovitis, Unspecified Shoulder

ICD-10-CM code M65.819 represents other synovitis and tenosynovitis of an unspecified shoulder. Tenosynovitis involves inflammation of the lining of the sheath that surrounds a tendon. This code is a billable, specific diagnosis within musculoskeletal system disorders, but the supplied sources do not establish payer coverage criteria or clinical treatment guidelines for this exact code. 2 3 5

Plain-language overview

Tenosynovitis is defined as inflammation of the lining of the sheath that surrounds a tendon, which is the cord joining muscle to bone. This inflammatory condition has a wide variety of causes and treatment considerations. 1 2

What this code represents

In the ICD-10-CM system, code M65.819 carries the descriptor "Other synovitis and tenosynovitis, unspecified shoulder" and is classified with the semantic type of Disease or Syndrome. The code is currently designated as active. 3 4

Coding details

Code M65.819 falls under subcategory M65.81 for shoulder conditions and has no child codes, making it a billable and specific code. This code is located in Chapter 13 for musculoskeletal system diseases under category M65 for synovitis and tenosynovitis. 5

The reference data for code M65.819 lists no inclusion terms, no "code first" instructions, and no "use additional code" instructions. This indicates a lack of mandatory sequencing or supplementary coding rules within the provided record. 5

Documentation considerations

A detailed history focusing on possible etiologies is essential for tenosynovitis, as the cause actively directs treatment. Documentation of injury, fever, ulceration, purulence, or longstanding arthritis helps distinguish between infectious and chronic systemic processes. 1

Clinical context

Tenosynovitis caused by infection needs to be treated right away, and an infected cut to the hands or wrists causing infectious tenosynovitis may be an emergency requiring surgery. If non-infectious tenosynovitis is not treated, the tendon may become permanently restricted or it may tear. 2

What the sources add

While clinical sources S1 and S2 describe tenosynovitis broadly and mention hands, wrists, and digits, coding sources S3 and S5 specify that M65.819 applies strictly to the shoulder. This comparison shows a clinical-to-coding distinction in anatomical specificity for this particular code. 1 2 3 5

Coverage and utilization context

The supplied coding sources establish that M65.819 is a billable code, but they do not mention payer coverage or reimbursement policies. A billable code designation confirms its use for claiming purposes but does not imply that a payer will cover the service. 3 5

Sources

1. Bookshelf — ncbi.nlm.nih.gov; accessed 2026-07-25.
2. Tenosynovitis: MedlinePlus Medical Encyclopedia — medlineplus.gov; accessed 2026-07-25.
3. Browse Code Systems — vsac.nlm.nih.gov; accessed 2026-07-25.
4. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-25.
5. ICD-10-CM Code M65.819 | Vero — veroscribe.com; accessed 2026-07-25.