ICD-10-CM · Other

M65.98

Inflammation of a synovial membrane or tendon sheath at an anatomical site that does not map to any other specifically coded location in the M65.9x subcategory.

Verified May 8, 2026 · 6 sources ↓

Status: Billable
Chapter: 13
Related CPT: 8
Region: Other

Drawn from CDCICD10DataCMSAAPC

Documentation tips

What should appear in the chart to support M65.98.

Source · Editorial brief grounded in 6 cited references ↓

Name the exact anatomical site in the note — even if it doesn't match a standard lateralized body-part label — so reviewers understand why a site-specific sibling code was not used.
Document whether the condition is infective or non-infective; if infective, M65.1x is required and M65.98 is excluded.
Record imaging findings (ultrasound, MRI) that confirm synovial thickening, tendon sheath fluid, or Doppler hyperemia to support medical necessity for procedures.
Specify if the presentation is bilateral or involves multiple sites — multiple sites maps to M65.99, not M65.98.
If conservative treatment history exists (NSAIDs, physical therapy, corticosteroid injection), document duration and response to support medical necessity for additional intervention.
Clarify whether the site could reasonably map to lower leg (M65.96x), thigh (M65.95x), or ankle/foot (M65.97x) before defaulting to M65.98 — those codes carry full laterality.

Related CPT procedures

Procedure codes commonly billed with M65.98. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

20600 $56.11

Needle aspiration and/or injection of a small joint or bursa — such as a finger or toe joint — performed without ultrasound guidance.

20605 $57.12

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular joint, or olecranon bursa — performed without ultrasound guidance.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

20611 $104.21

Aspiration or injection of a major joint or bursa performed under real-time ultrasound guidance, with permanent image documentation.

76942 $64.13

Ultrasound guidance for placing a needle, used to direct biopsies, aspirations, and injections, including the imaging supervision and interpretation.

29260 $28.72

Application of adhesive tape or bandaging to stabilize the elbow or wrist joint, limiting abnormal movement during healing.

29280 $30.06

Application of adhesive overlapping straps to the hand or finger to stabilize an injury, limit harmful movement, and support healing.

29540 $28.06

Strapping applied to the ankle and/or foot using overlapping adhesive tape to restrict movement and provide structural support.

Common coding pitfalls

The recurring mistakes coders make with M65.98 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Assigning M65.98 when a lateralized site-specific code exists — check the full M65.9x subcategory before using 'other site'; the tabular covers shoulder through ankle/foot with right/left/unspecified options.
Using M65.98 for infective tenosynovitis — infection requires M65.1x; M65.98 is restricted to unspecified (non-infective) inflammation.
Confusing 'other site' (M65.98) with 'multiple sites' (M65.99) — if more than one anatomical region is involved, M65.99 is correct.
Billing M65.98 when the condition maps to M70.x — chronic crepitant synovitis of hand/wrist and soft-tissue disorders from overuse/pressure are excluded from M65 by Type 1 Excludes; those require M70.- codes.
Applying M65.98 to a current tendon or ligament injury — acute injuries code to the appropriate S-code by body region, not M65.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

M65.98 applies when a provider documents unspecified synovitis or tenosynovitis at a site that is neither lateralized to a named body part covered by sibling codes (shoulder, upper arm, forearm, hand, thigh, lower leg, ankle/foot) nor identified as multiple sites (M65.99). This is a new code effective October 1, 2024 (FY2025), carried unchanged into FY2026. Use it when the inflamed synovium or tendon sheath involves an atypical or composite site — such as the sternoclavicular joint, sacroiliac region, or a chest-wall tendon — that the tabular list does not break out with its own lateralized code.

Before assigning M65.98, exhaust more specific options. If the condition is infective, use M65.1x. If it is calcific, use M65.2x. If it is trigger finger/thumb, use M65.3x. De Quervain's maps to M65.4. If the site is specified and the type is 'other' (not unspecified), the M65.8x subcategory with full site detail is preferable. M65.98 is the fallback only when both the anatomical site falls outside the listed body-part codes and the type cannot be further specified.

MS-DRG grouping places M65.98 in DRG 557 (Tendonitis, Myositis and Bursitis with MCC) or DRG 558 (without MCC). CMS also lists M65.98 as supporting medical necessity for nerve conduction studies and EMG (Article A56619), reflecting that tendon sheath inflammation can cause or mimic peripheral nerve entrapment symptoms. Parent code M65 carries a Type 1 Excludes for chronic crepitant synovitis of hand and wrist (M70.0-), current injuries (see injury codes by region), and soft-tissue disorders related to use/overuse/pressure (M70.-).

Sibling codes

Other billable codes under M65.9 (laterality / anatomic variants).

M65.99

Unspecified synovitis and tenosynovitis, multiple sites

M65.90

Unspecified synovitis and tenosynovitis, unspecified site

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What makes a site qualify as 'other site' for M65.98 versus using a more specific sibling code?

The M65.9x subcategory enumerates shoulder, upper arm, forearm, hand, thigh, lower leg, and ankle/foot with right/left/unspecified variants. If the affected tendon sheath or synovium sits outside those named regions — for example, the sternoclavicular area or abdominal wall tendon — and no other M65 subcategory fits, M65.98 applies. If any of the listed body parts could reasonably describe the site, use that code instead.

02Is M65.98 a new code or has it existed for years?

M65.98 is a new code effective October 1, 2024 (FY2025 ICD-10-CM), carried unchanged into FY2026. It did not exist in ICD-10-CM editions prior to FY2025, so claims for dates of service before October 1, 2024 cannot use it.

03Can M65.98 be used for infective tenosynovitis at an unusual site?

No. Infective (teno)synovitis requires a code from M65.1x regardless of site. M65.98 is unspecified — meaning the type is not further characterized as infective, calcific, or trigger — not simply that the etiology is unknown. When infection is confirmed or suspected, M65.1x with the appropriate site character is required.

04Does M65.98 support medical necessity for arthrocentesis or tendon sheath injection?

Yes. CMS Article A57079 (Injections — Tendon, Ligament, Ganglion Cyst, Tunnel Syndromes and Morton's Neuroma) includes M65.8x codes for specified synovitis/tenosynovitis by site; M65.98 falls under the unspecified umbrella and is generally accepted when documentation supports an injected tendon sheath at the coded site. Always verify individual payer LCD/NCD requirements, as some carriers require a more specific diagnosis code before authorizing injection procedures.

05What is the difference between M65.98 and M65.99?

M65.98 is 'other site' — one location that doesn't match the listed body-part codes. M65.99 is 'multiple sites' — synovitis or tenosynovitis involving more than one distinct anatomical region simultaneously. If bilateral elbow involvement is the reason for coding, M65.99 is more accurate than M65.98.

06Which MS-DRGs does M65.98 group to?

M65.98 groups to MS-DRG 557 (Tendonitis, Myositis and Bursitis with MCC) or MS-DRG 558 (Tendonitis, Myositis and Bursitis without MCC) under MS-DRG v43.0. The presence or absence of a major complication or comorbidity (MCC) drives the split.

07Can M65.98 appear on a workers' compensation or liability claim?

Yes. CMS designates M65.98 as a valid ICD-10 code for Section 111 NGHP mandatory reporting (liability insurance, no-fault, and workers' compensation), meaning it is accepted on those claim types when it accurately reflects the diagnosis.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (FY2026, effective October 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M65-M67/M65-/M65.98
03
cms.gov
https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=56619&ver=30
04
cms.gov
https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=57079&ver=7
05
cms.gov
https://www.cms.gov/medicare/coordination-benefits-recovery/overview/icd-code-lists
06
aapc.com
https://www.aapc.com/codes/icd-10-codes/M65.98

Mira Scribe

Mira's AI scribe captures the affected anatomical site by name, confirms absence of documented infection (ruling out M65.1x), records imaging findings (ultrasound or MRI evidence of synovial thickening or tendon sheath effusion), and notes whether the location is bilateral or isolated. This prevents defaulting to the unspecified-site code M65.90 when a site is actually named, and flags if a more specific sibling code (M65.95x–M65.97x) applies before M65.98 is selected.

See how Mira captures M65.98 documentation