2025 ICD-10-CM Diagnosis Code M65.90

Approximate Synonyms

The following list of clinical terms are approximate synonyms, alternative descriptions, or common phrases that might be used by patients, healthcare providers, or medical coders to describe the same condition. These synonyms and related diagnosis terms are often used when searching for an ICD-10 code, especially when the exact medical terminology is unclear. Whether you're looking for lay terms, similar diagnosis names, or common language alternatives, this list can help guide you to the correct ICD-10 classification.

Clinical Information

• Acquired Hyperostosis Syndrome

  syndrome consisting of synovitis; acne conglobata; palmoplantar pustulosis; hyperostosis; and osteitis. the most common site of the disease is the upper anterior chest wall, characterized by predominantly osteosclerotic lesions, hyperostosis, and arthritis of the adjacent joints. the association of sterile inflammatory bone lesions and neutrophilic skin eruptions is indicative of this syndrome.

• Synovitis

  inflammation of the synovial membrane.

• Synovitis, Pigmented Villonodular

  diffuse outgrowth arising from the synovial membrane; synovial bursa; or tendon sheath around the joint cavity, with extension to surrounding soft tissue. it is characterized by pigmented hemosiderin-containing macrophages; foam cells; and multinucleated giant cells. it usually occurs in the hands and feet, and around large joints, such as in the ankle and knee joints.

• Giant Cell Tumor of Tendon Sheath

  a tumor arising in the synovial membrane; synovial bursa; or tendon sheath. it is characterized by osteoclast-like giant cells; foam cells; pigmented hemosiderin-laden macrophages and inflammatory infiltrate. it is classified either as diffuse or localized tenosynovitis.

• Tendon Entrapment

  narrowing or stenosis of a tendon's retinacular sheath. it occurs most often in the hand or wrist but can also be found in the foot or ankle. the most common types are de quervain disease and trigger finger disorder.

• Tenosynovitis

  inflammation of the synovial lining of a tendon sheath. causes include trauma, tendon stress, bacterial disease (gonorrhea, tuberculosis), rheumatic disease, and gout. common sites are the hand, wrist, shoulder capsule, hip capsule, hamstring muscles, and achilles tendon. the tendon sheaths become inflamed and painful, and accumulate fluid. joint mobility is usually reduced.

• Synovial Membrane

  the inner membrane of a joint capsule surrounding a freely movable joint. it is loosely attached to the external fibrous capsule and secretes synovial fluid.

New 2025 ICD-10-CM Code

M65.90 is new to ICD-10-CM code set for the FY 2025, effective October 1, 2024. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2024. This is a new and revised code for the FY 2025 (October 1, 2024 - September 30, 2025).

M65.90 is grouped with Diagnostic Related Groups - MS-DRG Mapping

Diagnosis-Related Groups (DRGs) are used to classify hospital cases for billing and healthcare management. They help standardize how hospitals and other providers are reimbursed for inpatient care. Patients are grouped based on their principal diagnosis into broader categories called Major Diagnostic Categories (MDCs).

Once assigned to a DRG, the hospital receives a set payment for the patient’s care, regardless of the actual services provided. This fixed rate is intended to cover the typical cost of treating patients within that group. The payment amount depends on the DRG's relative weight, which reflects the expected complexity and cost of care based on the severity of the patient’s condition.

Diagnostic related groups encourage healthcare providers to focus on quality and efficiency in patient care while managing costs effectively. The diagnosis code is present in the following groups for version MS-DRG V42.0 applicable from 10/01/2024 through 09/30/2025.

Replacement Code

M6590 replaces the following previously assigned ICD-10-CM code(s):

• M65.9 - Synovitis and tenosynovitis, unspecified

Code History