A bony projection arising from the calcaneus of the right foot, classified as an enthesopathy under ICD-10-CM Chapter 13 (Diseases of the musculoskeletal system and connective tissue).

Documentation tips

What should appear in the chart to support M77.31.

Source · Editorial brief grounded in 4 cited references ↓

• Record laterality explicitly as 'right foot' or 'right heel' — not just 'heel spur' — so the coder can select M77.31 over M77.30 without querying the provider.
• Include imaging findings: specify the modality (X-ray, weight-bearing views), spur size in millimeters, and location (e.g., medial tubercle of the calcaneus).
• Document functional impact — morning heel pain, antalgic gait, inability to bear weight without pain — to establish medical necessity for orthotics, PT, or injection.
• If plantar fasciitis co-exists, document it as a separate finding with its own clinical description so both M77.31 and M72.21 can be coded concurrently.
• For bilateral spurs, explicitly state involvement of both right and left feet so M77.31 and M77.32 can both be assigned in the same encounter.

Related CPT procedures

Procedure codes commonly billed with M77.31. 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 M77.31 and adjacent codes.

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

• Defaulting to M77.30 (unspecified foot) when the note clearly documents the right side — this triggers payer specificity edits and can delay payment.
• Coding M77.31 alone when plantar fasciitis is also documented and separately treatable; both diagnoses should be coded when clinically supported.
• Applying M77.31 to Haglund's deformity without provider confirmation — Haglund's involves the posterior calcaneal prominence, not the plantar enthesis, and the correct code is disputed.
• Using a symptom code (e.g., M79.671 right foot pain) as an additional code once M77.31 is established — the enthesopathy code captures the underlying cause and symptom codes become redundant.
• Assuming a single bilateral code exists for calcaneal spurs; there is none in FY2026 ICD-10-CM — bilateral presentation requires both M77.31 and M77.32.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Sibling codes

Other billable codes under M77.3 (laterality / anatomic variants).