ICD-10-CM · Elbow

M70.21

Inflammation of the olecranon bursa — the fluid-filled sac overlying the posterior tip of the right elbow — caused by use, overuse, pressure, or occupational stress rather than infection.

Verified May 8, 2026 · 6 sources ↓

Status: Billable
Chapter: 13
Related CPT: 5
Region: Elbow

Drawn from CDCICD10DataAAPCIcdcodesCMS

Documentation tips

What should appear in the chart to support M70.21.

Source · Editorial brief grounded in 6 cited references ↓

Explicitly state 'right elbow' in the diagnosis — 'elbow bursitis' without laterality forces a downcode to M70.20 (unspecified).
Clarify non-infective status: if aspiration was performed, note fluid character (clear, straw-colored, non-purulent) to support M70.21 over septic bursitis codes.
Document the contributing activity or occupational exposure (e.g., repetitive leaning on elbow, prolonged pressure) to support the Y93.- external cause add-on required under M70 category guidance.
Record onset duration, prior conservative treatment attempted (padding, NSAIDs, aspiration), and any prior episodes to build a complete clinical picture for medical necessity review.
If imaging was obtained, note any findings such as bursal thickening or fluid accumulation on ultrasound or MRI to support the diagnosis.

Related CPT procedures

Procedure codes commonly billed with M70.21. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) 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.

73070 $29.39

Radiographic examination of the elbow joint using a minimum of 2 views to evaluate bone structure and surrounding tissues.

73080 $33.07

Radiologic examination of the elbow, complete, requiring a minimum of three views.

29999 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M70.21 and adjacent codes.

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

Assigning M70.21 for septic (infected) olecranon bursitis — infective bursitis belongs in the M71.- category, not M70.-; confirm non-infective status before using this code.
Using M70.20 (unspecified) when the provider has clearly documented the right side — always code to highest specificity; unspecified codes invite payer scrutiny.
Omitting the Y93.- external cause code when the disorder is of occupational or activity-related origin — the M70 category instructs 'use additional code' for this.
Confusing M70.21 with M70.31 (other bursitis of right elbow) — M70.21 is specific to the olecranon bursa; other elbow bursae (e.g., cubital) belong under M70.31.
Source 9 (PatientStudio) incorrectly maps M70.21 as 'Prepatellar bursitis, right knee' — that is a data error; M70.21 is definitively olecranon bursitis, right elbow per the CDC Tabular List.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

M70.21 is the correct code when the provider explicitly documents olecranon bursitis of the right elbow and the condition is non-infective in origin. It sits within the M70 category (soft tissue disorders related to use, overuse, and pressure), which carries an 'Includes' note for disorders of occupational origin. When the activity causing the disorder is known, append an external cause code from Y93.- to identify it.

If laterality is not documented, drop to M70.20 (unspecified elbow). For left-sided involvement, use M70.22. Do not use M70.21 for septic or infective olecranon bursitis — those cases require a code from M71.- (other bursopathies) with an appropriate organism code. The Excludes1 note under M70 bars use alongside M71.9- (bursitis NOS), so confirm the clinical picture is consistent with non-infective olecranon bursitis before assigning M70.21.

This code groups to MS-DRG 557 (Tendonitis, myositis and bursitis with MCC) or 558 (without MCC) under MS-DRG v43.0. For inpatient encounters, MCC/CC documentation will determine which DRG fires, so capture all comorbidities accurately.

Sibling codes

Other billable codes under M70.2 (laterality / anatomic variants).

M70.20

Olecranon bursitis, unspecified elbow

M70.22

Olecranon bursitis, left elbow

Frequently asked questions

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

01When should I use M70.21 versus M71.3- for olecranon bursitis?

Use M70.21 for non-infective olecranon bursitis of the right elbow tied to use, overuse, or pressure. Use M71.3- (other bursitis) categories when the etiology is infective or clearly not occupational/activity-related overuse. If the bursa is infected, a separate organism code is also required.

02Do I need an external cause code with M70.21?

Yes, when the causative activity is known. The M70 category instructs 'use additional external cause code to identify activity causing disorder (Y93.-).' This is especially important for workers' compensation claims with documented occupational exposure.

03Can I code M70.21 and M70.22 together for bilateral olecranon bursitis?

Yes. There is no bilateral combination code under M70.2, so code both M70.21 (right) and M70.22 (left) when bilateral involvement is documented. Do not use M70.20 (unspecified) as a bilateral stand-in — it indicates unknown laterality, not bilateral disease.

04What CPT codes are most commonly paired with M70.21?

Aspiration or injection of the olecranon bursa pairs with CPT 20610 (arthrocentesis, aspiration and/or injection, major joint or bursa) or 20605 (intermediate joint). Elbow X-rays use 73070 or 73080. Ultrasound guidance, if documented, adds 76942.

05Is M70.21 valid for traumatic olecranon bursitis caused by a fall?

M70.21 is acceptable when the provider documents olecranon bursitis following trauma, as the code category covers pressure and overuse mechanisms. However, if the provider explicitly diagnoses a distinct acute traumatic bursitis tied to an injury event, some coders argue an S-code injury may better capture the encounter — query the provider and document the clinical reasoning. A Y93.- or external cause W-code should accompany the claim regardless.

06What MS-DRGs does M70.21 map to for inpatient encounters?

M70.21 groups to MS-DRG 557 (Tendonitis, myositis and bursitis with MCC) or MS-DRG 558 (without MCC) under MS-DRG v43.0. Accurate comorbidity and MCC documentation determines which DRG fires.

07Is M70.21 a chronic condition indicator?

No. M70.21 is not flagged as a chronic condition in the ICD-10-CM classification. It represents an active soft-tissue disorder that may be acute or recurrent, but does not carry a chronic condition designation for HCC or quality-measure purposes.

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)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M70-M79/M70-/M70.21
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M70.21
04
aapc.com
https://www.aapc.com/codes/coding-newsletters/my-orthopedic-coding-alert/icd-10-do-you-know-how-to-report-olecranon-bursitis-find-out-148808-article
05
icdcodes.ai
https://icdcodes.ai/diagnosis/olecranon-bursa/documentation
06
cms.gov
https://www.cms.gov/files/document/fy-2025-icd-10-cm-coding-guidelines.pdf

Mira AI Scribe

The Mira AI Scribe captures laterality (right elbow), bursal location (olecranon), non-infective characterization, relevant occupational or activity history, and any aspiration fluid description from the encounter note — preventing a downcode to unspecified M70.20, a mismatch to septic bursitis codes, or a missing Y93.- external cause code that the M70 category requires.

See how Mira captures M70.21 documentation