A fluid-filled, non-neoplastic cyst arising from the synovial lining of a bursa, reported when the anatomical site has not been documented or cannot be determined.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 5
- Region
- General
Documentation tips
What should appear in the chart to support M71.30.
Source · Editorial brief grounded in 5 cited references ↓
- Record the anatomical site by name (e.g., subacromial, olecranon, trochanteric) — if any site is named, a child code is available and M71.30 is no longer appropriate.
- Document laterality (right or left) whenever the provider can determine it; unspecified-site M71.30 is only valid when site is truly unknown or undocumented.
- Note imaging modality and key findings (ultrasound or MRI confirmation, cyst size, fluid characteristics) to support medical necessity for aspiration or injection procedures.
- Distinguish clearly between a bursal cyst and a ganglion cyst in the assessment — the two map to different ICD-10-CM categories and cannot be used interchangeably.
- If a rupture is suspected or confirmed, the correct code shifts to M66.1- (synovial cyst with rupture); document rupture status explicitly so the coder can select correctly.
Related CPT procedures
Procedure codes commonly billed with M71.30. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M71.30 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M71.30 when a site-specific child code exists — if the note says 'olecranon bursal cyst, right,' the correct code is M71.321, not M71.30.
- Confusing bursal cyst (M71.3x) with ganglion cyst (M67.4x) — the tabular has reciprocal Type 2 Excludes notes; verify the provider's diagnosis term before coding.
- Applying M71.30 to a Baker's cyst — popliteal synovial cysts have their own category at M71.2x and must not be coded to the M71.3x series.
- Defaulting to M71.30 instead of M66.1- when the note or imaging documents cyst rupture — rupture changes both the code family and clinical management context.
- Selecting M71.30 for bursitis caused by repetitive use or pressure — those conditions belong in M70.- and are excluded from the M71 category.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M71.30 is the fallback code for a bursal (synovial) cyst when no specific body site is documented in the clinical record. The M71.3x family covers bursal cysts that are distinct from Baker's cyst (M71.2x) and from synovial cysts with rupture (M66.1-, excluded). If the provider documents a site — shoulder, elbow, wrist, hand, hip, knee, ankle/foot, or other — you must use the site-specific child code, not M71.30. Reserve M71.30 only when the note genuinely omits anatomic location or the cyst involves a site with no dedicated subcode.
M71.30 is listed by CMS as a supporting diagnosis for bursa injection procedures, so it can anchor medical necessity for aspiration or corticosteroid injection when a site-specific code is unavailable. It maps to MS-DRG 557 (Tendonitis, Myositis and Bursitis with MCC) and 558 (without MCC) under DRG v43.0. Do not use M71.30 for a ganglion cyst — those map to M67.4x; the tabular explicitly excludes bursal cyst from the ganglion category and vice versa.
Also excluded from M71.3x: bursitis related to use, overuse, or pressure (M70.-), enthesopathies (M76-M77), and bunion (M20.1). If the imaging report or clinical note identifies the cyst as arising from a specific joint or bursa and laterality is stated, move to the most specific available child code before defaulting to M71.30.
Sibling codes
Other billable codes under M71.3 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01When is M71.30 the correct code instead of a child code like M71.321?
02Can M71.30 be used for a Baker's cyst?
03Is M71.30 accepted by CMS to support medical necessity for a bursa injection?
04What is the difference between M71.30 and M67.4x?
05If imaging confirms rupture of a bursal cyst, does M71.30 still apply?
06What CPT codes are commonly reported with M71.30?
07Does M71.30 require a 7th-character extension?
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 Oct 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M70-M79/M71-/M71.30
- 03icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M70-M79/M71-/M71.3
- 04aapc.comhttps://www.aapc.com/codes/icd-10-codes/M71.30
- 05cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=60304&ver=3
Mira AI Scribe
Mira captures the provider's documented anatomical site (or explicit absence of one), laterality, imaging findings (ultrasound or MRI confirming fluid-filled bursal cyst), and any noted rupture status. This prevents a fallback to M71.30 when a site-specific child code is justified, and flags when M66.1- (ruptured cyst) or M67.4x (ganglion) should be used instead — reducing payer audit exposure from nonspecific coding.
See how Mira captures M71.30 documentation