M11.20

M11.20 captures calcium pyrophosphate crystal deposition in cartilage (chondrocalcinosis) when the affected joint site is not documented or cannot be specified — encompassing both sporadic and secondary forms that don't qualify as familial chondrocalcinosis.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 12
Region: General

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M11.20.

Source · Editorial brief grounded in 5 cited references ↓

Name the specific joint involved (e.g., 'right knee,' 'left wrist') at every encounter — a named joint triggers a more specific M11.2x code and avoids the unspecified fallback.
If imaging (X-ray, ultrasound, CT) identifies periarticular or intra-articular calcification, document the exact joint location in the impression or clinical note to support site-specific coding.
When pseudogout is the clinical diagnosis, confirm the provider explicitly links it to calcium pyrophosphate crystal deposition and document the joint aspirated or imaged — pseudogout maps to M11.2x, not a separate code.
For multi-joint presentations, document each affected joint separately; M11.29 (multiple sites) is preferable to M11.20 (unspecified site) when more than one joint is identified.
Record whether the chondrocalcinosis is idiopathic/sporadic, secondary to metabolic disease (hyperparathyroidism, hemochromatosis, hypomagnesemia), or familial — this distinction drives code selection between M11.0x, M11.1x, and M11.2x.

Related CPT procedures

Procedure codes commonly billed with M11.20. 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.

73560 $34.40

Radiologic examination of the knee joint, one or two views, unilateral.

73562 $42.42

Three-view radiographic examination of the knee joint, capturing anteroposterior, lateral, and a third angle such as a sunrise or oblique view.

73564 $49.43

Radiologic examination of the knee consisting of four or more views, including oblique and tunnel projections, for a complete diagnostic workup.

73580 $117.24

Radiologic examination of the knee joint using arthrography — contrast injection and radiological supervision and interpretation only.

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

99215 $192.39

Highest-level office or outpatient E/M visit for an established patient, qualifying via high-complexity medical decision making or 40–54 minutes of total provider time on the date of service.

77080 View procedure details

85590 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M11.20 and adjacent codes.

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

Defaulting to M11.20 when the provider dictates 'chondrocalcinosis of the knee' — a named joint requires M11.261 (right), M11.262 (left), or M11.269 (unspecified knee), not M11.20.
Confusing familial chondrocalcinosis (M11.1x) with other/NOS chondrocalcinosis (M11.2x) — family history alone does not qualify for M11.1x; the provider must document a familial/hereditary form.
Using M11.20 for pseudogout when the affected joint is documented — pseudogout maps to M11.2x with the appropriate site digit, not to the unspecified code.
Billing M11.20 on follow-up encounters after a specific joint has been identified on prior imaging or aspiration — payers expect a site-specific code once laterality and anatomy are established.
Sequencing M11.20 as a secondary code when it is the primary reason for the orthopedic visit — chondrocalcinosis should be the principal diagnosis when the encounter is driven by that condition.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M11.20 is the unspecified-site fallback within the M11.2 (Other chondrocalcinosis) subcategory. Use it only when documentation genuinely fails to identify which joint is involved. The moment a joint is named — knee, shoulder, wrist, hip, elbow, ankle/foot, or vertebrae — a site-specific code in the M11.21–M11.29 range must be used instead. M11.20 also carries the 'Chondrocalcinosis NOS' inclusion term, so it functions as the default landing code when a provider simply documents 'chondrocalcinosis' with no further anatomical detail.

Chondrocalcinosis coded under M11.2 (and therefore M11.20) is distinct from familial chondrocalcinosis (M11.10–M11.19) and hydroxyapatite deposition disease (M11.0x). If the provider documents pseudogout, the correct home is still M11.2x — pseudogout is the clinical syndrome caused by calcium pyrophosphate crystals, and ICD-10-CM maps it here. Confirm with the ordering provider whether joint-fluid analysis or imaging identified a specific site before defaulting to the unspecified code.

In orthopedic practice, M11.20 appears most often on initial workup notes where imaging shows periarticular calcification but the dictation omits the joint name, or in multi-joint presentations where a single dominant site hasn't been established. Payers may flag the unspecified code on repeat claims — query the provider before the second encounter if a specific joint is now known.

Sibling codes

Other billable codes under M11.2 (laterality / anatomic variants).

M11.29

Other chondrocalcinosis, multiple sites

M11.28

Other chondrocalcinosis, vertebrae

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01When is M11.20 the correct code instead of a more specific M11.2x code?

Use M11.20 only when the provider's documentation contains no reference to which joint is affected. As soon as a joint name appears — even 'knee' without laterality — move to the corresponding site-specific code (e.g., M11.269 for unspecified knee).

02Is pseudogout coded with M11.20?

Pseudogout maps to the M11.2x subcategory, but use M11.20 only if the affected joint is entirely undocumented. If the provider identifies the joint, assign the site-specific code. The clinical term pseudogout does not have its own separate ICD-10-CM code.

03How does M11.20 differ from M11.10 (familial chondrocalcinosis, unspecified site)?

M11.10 requires documented familial or hereditary chondrocalcinosis — the provider must establish a hereditary etiology. M11.20 covers sporadic, secondary (metabolic), and NOS presentations where a familial pattern has not been established.

04Can M11.20 and a metabolic disorder code be reported together?

Yes. When chondrocalcinosis is secondary to a metabolic condition (e.g., hyperparathyroidism E21.x, hemochromatosis E83.1x, hypomagnesemia E83.42), code the underlying condition first per etiology/manifestation sequencing conventions, then M11.20.

05Will payers accept M11.20 on repeat claims after an initial workup?

Some payers flag repeated unspecified-site codes as incomplete documentation. If imaging or aspiration at the initial encounter identified a joint, update to a site-specific M11.2x code at subsequent visits to reduce audit risk.

06Is M11.20 valid for both inpatient and outpatient billing?

Yes, M11.20 is a fully billable ICD-10-CM code valid for all care settings effective October 1, 2025 under the FY2026 code set. Apply standard outpatient first-listed vs. inpatient principal diagnosis sequencing rules as appropriate.

07Does chondrocalcinosis involving the femur default to M11.20?

No. Chondrocalcinosis is a joint disease, not a bone disease. If the provider documents femoral involvement without specifying a joint, query for clarification — the femur is part of both the hip and knee joints, and a site-specific code (M11.25x for hip or M11.26x for knee) is required once the joint is confirmed.

Sources & references

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

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M05-M14/M11-/M11.20
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M11.20
04
aapc.com
https://www.aapc.com/codes/icd-10-codes/M11
05
cms.gov
https://www.cms.gov/files/document/fy-2025-icd-10-cm-coding-guidelines.pdf

Mira AI Scribe

Mira's AI scribe captures the joint name, laterality, and imaging findings (calcification location on X-ray or ultrasound, synovial fluid crystal analysis) from the encounter note. If the provider dictates a specific joint, the scribe flags the appropriate site-specific M11.2x code rather than M11.20, preventing an unspecified-site assignment that can trigger payer scrutiny on repeat claims.

See how Mira captures M11.20 documentation