M91.90 identifies juvenile osteochondrosis of the hip and pelvis when neither the specific subtype nor the affected leg is documented. Both the type of juvenile osteochondrosis and laterality are unspecified.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 8
- Region
- Hip
Documentation tips
What should appear in the chart to support M91.90.
Source · Editorial brief grounded in 4 cited references ↓
- Document the affected side explicitly — 'right hip,' 'left hip,' or 'bilateral' — so you can step up to M91.91 or M91.92 and avoid the unspecified fallback.
- Identify the subtype by name when possible (e.g., Legg-Calvé-Perthes, coxa plana, pseudocoxalgia) so a more specific M91.1x–M91.8x code can be assigned.
- Record imaging findings — X-ray, MRI, or bone scan results — including any signs of femoral head fragmentation, flattening, or joint space changes that support the diagnosis and subtype.
- Note patient age at diagnosis; juvenile osteochondrosis applies to skeletally immature patients, and the record should reflect that the growth plates are open.
- If chondrolysis is present, document it separately so the add-on instruction to code M94.3 is actionable.
Related CPT procedures
Procedure codes commonly billed with M91.90. 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 M91.90 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M91.90 when laterality is documented: if the note says 'left hip,' use M91.92, not M91.90.
- Coding M91.90 alongside M93.0x (slipped upper femoral epiphysis, nontraumatic): the Excludes1 note at the M91 category level prohibits using any M91 code with M93.0x simultaneously.
- Defaulting to M91.90 when the clinical presentation is classic Legg-Calvé-Perthes: that condition maps to M91.1x, not M91.9x.
- Omitting M94.3 when chondrolysis is documented alongside the osteochondrosis: the tabular instructs an additional code for associated chondrolysis.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
M91.90 is the fallback code within the M91.9 subgroup when a pediatric patient presents with hip or pelvic osteochondrosis and the documentation does not specify which leg is involved and does not identify a distinct subtype. The M91 category covers a spectrum of juvenile osteochondroses including Legg-Calvé-Perthes disease (M91.1x), coxa plana (M91.2x), pseudocoxalgia (M91.3x), coxa magna (M91.4x), and other specified forms (M91.8x). Use M91.90 only when the clinical record genuinely cannot support a more specific code.
Before assigning M91.90, confirm that more specific codes are truly unavailable. If imaging or clinical notes identify the affected side, use M91.91 (right leg) or M91.92 (left leg). If the condition is further characterized — for example, Legg-Calvé-Perthes — step up to the appropriate M91.1x code. Slipped upper femoral epiphysis (nontraumatic) is an Excludes1 condition under M91; never code M93.0x alongside any M91 code.
This code applies to patients whose skeletal development is still active. Encounters typically involve pediatric or adolescent patients, and the code may appear with procedure codes for imaging, bracing, or surgical intervention such as hip osteotomy or core decompression. If chondrolysis is also documented, the tabular note at the M91 category level instructs you to add M94.3.
Sibling codes
Other billable codes under M91.9 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01When is M91.90 the correct code instead of M91.91 or M91.92?
02Can M91.90 be used for Legg-Calvé-Perthes disease?
03Can M91.90 and M93.0x be reported together on the same claim?
04Is there an additional code required when chondrolysis accompanies the osteochondrosis?
05Does M91.90 require a 7th-character extension?
06What is the parent code relationship between M91.9 and M91.90?
07What CPT codes commonly appear with M91.90 on the same claim?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
Mira AI Scribe
Mira AI Scribe captures the patient's age, affected side (right, left, or bilateral), imaging findings (femoral head morphology, joint space, growth plate status), and any named subtype (Legg-Calvé-Perthes, coxa plana, etc.) from the encounter note. This specificity lets the coder step up from the M91.90 fallback to a laterality- and subtype-specific code, preventing downcoding, payer queries, and audit flags tied to unspecified-leg diagnoses in a pediatric hip claim.
See how Mira captures M91.90 documentation