M77.52 identifies enthesopathy affecting the tendon or ligament insertion sites of the left foot and ankle, excluding plantar fasciitis, Achilles tendinitis, and other named enthesopathies with dedicated codes.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 11
- Region
- Foot & ankle
Documentation tips
What should appear in the chart to support M77.52.
Source · Editorial brief grounded in 4 cited references ↓
- Explicitly document 'left' foot or ankle — laterality cannot be inferred from operative notes alone and missing it forces a downcode to M77.50 (unspecified).
- Identify the specific tendon or ligament insertion site affected (e.g., tibialis posterior insertion, anterior ankle capsule origin) to support medical necessity and distinguish from more specific named enthesopathies.
- Record imaging findings — X-ray evidence of calcific deposits, enthesophytes, or cortical irregularity at an insertion site strengthens the diagnosis and justifies advanced imaging or injection procedures.
- Document conservative care history (physical therapy, orthotics, NSAIDs) if the patient is progressing to injection or surgical intervention; payers commonly require this for M77.52-linked procedures.
- Confirm the condition is not plantar fasciitis (M72.2), Achilles tendinitis (M76.62), or peroneal tendinitis (M76.72-) before assigning M77.52 — those codes take priority when the named structure is documented.
Related CPT procedures
Procedure codes commonly billed with M77.52. 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 M77.52 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M77.52 when plantar fasciitis (M72.2) or Achilles tendinitis (M76.62) is the documented diagnosis — M77.52 is a residual 'other' code and should not displace named enthesopathies with specific codes.
- Using M77.50 (unspecified) when the provider clearly documents left-sided involvement — failure to capture laterality results in a less specific code that may trigger payer queries or audit flags.
- Coding M77.52 alongside M25.7- (osteophyte) for the same site — M77 has an Excludes2 note for osteophyte; if an osteophyte is the primary finding, M25.7- may be the more accurate code.
- Confusing enthesopathy with bursitis — M77 carries an Excludes1 for bursitis NOS (M71.9-); these are not interchangeable and cannot be coded together when referring to the same condition.
- Failing to update historical claims coded before FY2020: the pre-2020 descriptor was 'Other enthesopathy of left foot' (no ankle). If the ankle was the true site of pathology, retroactive correction may be warranted for audit purposes.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
Use M77.52 when the provider documents enthesopathy of the left foot or ankle that does not meet the criteria for a more specific code in the M77 category. Plantar fasciitis (M72.2), Achilles tendinitis (M76.6-), and peroneal tendinitis (M76.7-) each have their own codes — M77.52 is the residual category for left-sided enthesopathies at the foot and ankle that fall outside those named conditions. Examples include insertional tendinopathy of the tibialis anterior or posterior at their foot attachments, or calcific enthesopathy of the ankle ligament origins, when the provider's documentation doesn't align with a more specific subcategory.
M77.52 sits under parent code M77.5 (Other enthesopathy of foot and ankle). Its sibling codes are M77.50 (unspecified side) and M77.51 (right foot and ankle). Laterality is required at the 5th-character level: use M77.52 only when left-sided involvement is explicitly documented. The M77 category carries Excludes1 notes for bursitis NOS (M71.9-) and Excludes2 notes for bursitis due to use/overuse/pressure (M70.-), osteophyte (M25.7-), and spinal enthesopathy (M46.0-) — verify those conditions are not the true diagnosis before assigning M77.52.
This code was revised in FY2020 to add 'and ankle' to the descriptor, expanding its scope beyond foot-only sites. If you're coding a pre-2020 encounter, confirm the applicable code year.
Sibling codes
Other billable codes under M77.5 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M77.52 and M72.2 (plantar fasciitis)?
02Can M77.52 be used for Achilles tendinitis at its calcaneal insertion?
03When should I use M77.50 instead of M77.52?
04Is M77.52 appropriate for a calcific enthesopathy seen on X-ray at the ankle?
05Can M77.52 be used as a primary diagnosis for injection billing (e.g., CPT 20550)?
06Did the M77.52 descriptor change at any point?
07Is bilateral foot and ankle enthesopathy coded with M77.52 alone?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M70-M79/M77-/M77.52
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M77.52
- 04cms.govhttps://www.cms.gov/files/document/fy-2025-icd-10-cm-coding-guidelines.pdf
Mira AI Scribe
Mira captures left-side laterality, the specific insertion site (e.g., tibialis posterior at navicular, anterior talofibular ligament origin), imaging findings such as enthesophyte or calcific deposit, and prior conservative treatment documented in the encounter — preventing a downcode to M77.50 (unspecified) and blocking audit flags that arise when procedure codes for left-foot injections or excisions are submitted without laterality-matched diagnoses.
See how Mira captures M77.52 documentation