M24.7 identifies protrusio acetabuli, a structural deformity in which the acetabular floor is abnormally deep, causing the femoral head to migrate medially into or through the medial wall of the pelvis.

Documentation tips

What should appear in the chart to support M24.7.

Source · Editorial brief grounded in 4 cited references ↓

• Specify whether the protrusion is primary (idiopathic/Otto's disease) or secondary to an underlying condition; if secondary, code the underlying cause first and use M24.7 as an additional code.
• Record imaging findings that confirm the diagnosis — AP pelvis radiograph with Köhler's line or iliopectineal line measurement, or CT findings showing medial wall depth and thickness.
• Document laterality by name (right hip, left hip, or bilateral) in the clinical note even though M24.7 carries no laterality subcode; this supports medical necessity narratives for payers.
• If the patient is being evaluated or consented for THA, note how protrusion affects planned component positioning and whether structural allograft or augmentation is anticipated — this supports higher-complexity E/M coding.
• When rheumatoid arthritis, Paget's disease, or another systemic condition is the underlying cause, list that diagnosis as the principal code and sequence M24.7 as secondary.

Related CPT procedures

Procedure codes commonly billed with M24.7. 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 M24.7 and adjacent codes.

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

• Attempting to add a laterality digit to M24.7 — the code has no 5th or 6th character for side; it is valid as a 4-character billable code only.
• Coding only the underlying condition (e.g., rheumatoid arthritis) and omitting M24.7, which causes loss of specificity that payers use to justify complex surgical authorization.
• Confusing protrusio acetabuli with coxa profunda — coxa profunda refers to a deep socket without medial wall breach and may not meet clinical criteria for M24.7; confirm the radiologist's or surgeon's specific terminology before coding.
• Failing to add a secondary OA code (M16.1x or M16.2) when protrusion has progressed to secondary osteoarthritis — M24.7 alone does not capture the arthritic component.
• Using an injury code (S-series) for a chronic, non-traumatic protrusion — M24.7 is the correct choice for the structural deformity regardless of its origin unless an acute fracture of the medial wall is the primary event.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Sibling codes

Other billable codes under M24 (laterality / anatomic variants).