M77.51 captures enthesopathy affecting tendon and ligament insertion sites of the right foot and ankle — excluding plantar fasciitis, Achilles enthesopathy, and calcaneal spur, which have their own dedicated codes.

Documentation tips

What should appear in the chart to support M77.51.

Source · Editorial brief grounded in 4 cited references ↓

• Specify laterality as 'right' explicitly in the clinical note — 'right foot and ankle enthesopathy' maps directly to M77.51 and prevents a fallback to M77.50 (unspecified).
• Document which named enthesopathies have been ruled out (plantar fasciitis, calcaneal spur, Achilles enthesopathy) to justify the 'other' classification and withstand audit scrutiny.
• Record the specific tendon or insertion site involved (e.g., flexor hallucis longus, peroneal tendon insertion) even when the code doesn't require it — this supports medical necessity for imaging and injection CPT codes.
• If the condition is bilateral, document both sides clearly so M77.51 (right) and M77.52 (left) can be assigned together rather than defaulting to unspecified.
• Capture conservative treatment history (physical therapy, orthotics, NSAIDs) when the encounter supports a higher-level E/M or prior authorization for advanced imaging or injections.

Related CPT procedures

Procedure codes commonly billed with M77.51. 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 M77.51 and adjacent codes.

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

• Using M77.50 (unspecified) when the provider clearly documents the right side — always assign M77.51 when laterality is in the record.
• Assigning M77.51 for plantar fasciitis or calcaneal spur — those have dedicated codes (M72.2 and M77.31 respectively) and are not 'other' enthesopathies.
• Coding M77.51 for bursitis caused by repetitive use or occupational pressure — those cases belong under M70.- (bursitis due to use, overuse and pressure), which is an Excludes2 note at the M77 category level.
• Forgetting to assign M77.52 alongside M77.51 when the provider documents bilateral involvement — bilateral coding is required; there is no single bilateral code for M77.5.
• Applying a 7th-character extension to M77.51 — M-codes do not use 7th-character encounter extensions; those apply to injury S-codes only.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Sibling codes

Other billable codes under M77.5 (laterality / anatomic variants).