ICD-10 code M91.91: Juvenile osteochondrosis of hip and pelvis

Key takeaways

ICD-10 code M91.91 covers juvenile osteochondrosis of hip and pelvis, unspecified, right leg. It is billable in ICD-10-CM and took effect on October 1, 2025.

M91.91 is billable but its parent M91.9 is not. Never submit the parent code when a laterality subcode applies.

Legg-Calvé-Perthes disease codes to M91.1x rather than M91.9x. Using M91.91 for a documented case is a coding error that draws denials.

Practice management software like Pabau keeps the laterality note and the diagnosis on one patient record, so the coder is not guessing at claim time.

ICD-10 code M91.91 is the billable code for juvenile osteochondrosis of hip and pelvis, unspecified, right leg. It sits beneath the parent code M91.9, which cannot go out on a claim by itself.

Two mistakes drive most M91.91 denials. Coders submit the non-billable parent M91.9, or they reach for M91.91 when the record documents Legg-Calvé-Perthes disease. That named condition belongs to M91.1. Both mistakes start in the clinical note rather than the billing module, which is where they are cheapest to fix.

ICD-10 code M91.91: Quick reference and billability status

ICD-10 code M91.91 is a valid, billable ICD-10-CM diagnosis code for fiscal year 2026. It took effect on October 1, 2025, under the FY2026 edition of the CDC/NCHS ICD-10-CM code set. Clinicians and coders can submit it in HIPAA-covered transactions.

The billability distinction matters. M91.91 is specific enough to carry a claim on its own. Its parent M91.9 is not, because HIPAA requires covered entities to use the most specific code available.

Submitting M91.9 when M91.91 is clinically supported invites a rejection or an audit flag. Once the right code sits on the patient record, Pabau’s claims management tools pull it into a pre-filled claim and track what happens next.

M91.9 subcodes: Laterality breakdown

M91.9 has three billable child codes, separated only by laterality. Picking the wrong one from incomplete documentation is a leading denial trigger in pediatric orthopedics.

M91.90 is the right choice only when the treating clinician genuinely cannot determine which side is involved. That should be rare. A physical examination or an imaging report confirms right or left involvement in almost every pediatric hip case.

Defaulting to M91.90 when the notes do document laterality is a coding error, not a safe fallback. Accurate clinical record documentation of the affected hip is what drives the code choice.

Clinical condition: Juvenile osteochondrosis of the hip

Juvenile osteochondrosis of the hip covers a group of disorders in which blood supply to the femoral head is disrupted during skeletal development. The result is avascular necrosis, bone fragmentation, and eventual remodeling. It mostly affects children between the ages of 4 and 10.

The presenting symptoms are hip pain, a limp, and restricted range of motion. Several other pediatric hip conditions look the same at first, which is why the specific code matters for both billing and clinical tracking.

Legg-Calvé-Perthes disease and related conditions under M91

Legg-Calvé-Perthes disease, or LCPD, is the named condition under M91.1 rather than M91.9. This one distinction causes more errors than anything else in the code group.

When the clinical record documents LCPD, the M91.1x codes apply. M91.11 covers the right hip and M91.12 covers the left. Using M91.91 for a confirmed LCPD case is incorrect, and it can create medical necessity conflicts during payer review.

The M91 category also carries several related terms in the official ICD-10-CM applicable-to notes. They help coders who search by clinical terminology rather than by code number.

• Coxa plana describes a flattened femoral head following avascular necrosis.
• Pseudocoxalgia is an older term for LCPD-like hip pain in children.
• Osteochondrosis of head of femur is the anatomical descriptor for the same pathological process.
• Juvenile osteochondrosis of hip and pelvis is the category term covering M91.0 through M91.9.

Pediatric hip complaints turn up regularly in physical therapy caseloads and in osteopathy practices, particularly where young athletes are involved.

All M91 group codes: Juvenile osteochondrosis of hip and pelvis

The M91 group covers juvenile osteochondrosis of the hip and pelvis in full. Choosing correctly within the group means knowing whether a named condition is documented, and which leg is affected. The table below lists every M91 code according to the CMS ICD-10-CM code files.

Juvenile osteochondrosis documented at a site outside the hip and pelvis leaves this group entirely. M92.9 is where it lands when the site is not specified. For anything that looks like an edge case, check the current FY2026 tabular list before you submit.

Coding guidelines for juvenile osteochondrosis of the hip

The official ICD-10-CM coding instructions set out several rules that govern when M91.91 applies. The AAPC’s ICD-10 code index is a quick way to compare a sibling code while you work. Review both before submitting a pediatric musculoskeletal claim.

• Use M91.91 only when the condition type is unspecified. Legg-Calvé-Perthes disease, coxa plana, pseudocoxalgia, and coxa magna each have their own M91.x codes. M91.91 applies only when the documentation does not name the type.
• Laterality has to be supported by documentation. The right-leg designation must come from the encounter note, a radiology report, or physical examination findings. Coders cannot assign laterality on assumption.
• The record has to support the juvenile designation. Payers may ask for notes confirming the patient is still skeletally immature. They may also ask for radiographic or clinical confirmation of hip and pelvis involvement.
• Check whether additional codes apply. Hip pain takes its own code from the M25.55 series, and M25.551 is the one for the right hip. Avascular necrosis codes separately under M87.

Excludes notes and code interactions

The M91 category carries Excludes notes in the official ICD-10-CM tabular list. They govern what cannot be coded alongside M91.91, and what needs a separate code entirely.

• Excludes1, meaning the two cannot be coded together: slipped upper femoral epiphysis, M93.0x. A documented slipped epiphysis replaces M91.x coding rather than supplementing it, because the two are distinct pathological processes.
• Avascular necrosis, M87.x: necrosis is sometimes documented as a consequence of the osteochondrosis rather than a separate diagnosis. In that case, sequencing guidance from the attending clinician decides the principal diagnosis.

Practices that run digital intake forms can prompt clinicians for laterality and condition type at the point of care. That single prompt makes the whole M91 coding workflow more straightforward.

2026 ICD-10-CM updates: Is ICD-10 code M91.91 still valid?

Yes. M91.91 remains active and valid in the FY2026 edition of ICD-10-CM, effective October 1, 2025. The FY2026 cycle changed nothing about its description, its billability, or its place in the hierarchy. The code has been stable across recent fiscal years.

Codes in every ICD-10-CM chapter can still be revised, retired, or expanded each October. Check M91.91 against the official CMS code files when a new coding year opens, even though it has held steady so far.

How to document M91.91 in your EMR and practice management software

Accurate M91.91 documentation starts in the clinical encounter note, not in the billing workflow. These five steps cover the chain from assessment through to claim submission.

1. Document laterality in the clinical note. The attending clinician needs to write right hip or right leg in the encounter note, the physical exam findings, or the imaging interpretation. This one step is what separates M91.91 from M91.90.
2. Name the condition type when it is known. Record LCPD, coxa plana, pseudocoxalgia, or coxa magna by name if one of them is the working diagnosis. A named condition lets the coder pick a more specific M91.x code from the outset.
3. Confirm age and skeletal maturity. M91.91 is a juvenile code. The record should show the patient is skeletally immature, typically under age 16, to support that designation in an audit.
4. Search for the code by keyword in your EMR. Most systems let you search descriptions rather than digits. A search for juvenile osteochondrosis hip right surfaces M91.91, M91.11, and neighboring codes for comparison. Confirm you have M91.91 and not a sibling before saving.
5. Link the diagnosis to the procedure codes. Pair M91.91 with the CPT codes for the services delivered, such as the orthopedic evaluation, imaging review, or physical therapy assessment. Payers match diagnosis to procedure, so a mismatch triggers medical necessity review.

Structured clinical workflows help here, especially where assessment templates carry a laterality prompt. Pabau’s automated workflow tools build that prompt into intake and assessment templates, so the side is captured at the visit rather than inferred later.

High-volume pediatric caseloads sit mostly with physical therapy and chiropractic practices, where the M91 family comes up often. Connecting the diagnosis on the record to the billing module in your practice management software closes the distance between the note and the claim.

How Pabau keeps laterality on the record and on the claim

In most practices the laterality evidence lives in one place and the claim is built in another. The radiologist names the right hip in a PDF. The coder reads an encounter note that says hip pain, and M91.90 goes out on the claim. The correction arrives weeks later as a denial.

Pabau keeps the assessment, the treatment note, the imaging document, and the invoice on a single patient record. You can build the laterality question into the intake or assessment template, so the side is captured before anyone starts coding. The diagnosis then stays attached to the visit that produced it.

When it is time to bill, Pabau’s claims management tools pull what is already on that record into a pre-filled claim and track its status. Nobody retypes a side from a scanned report, so fewer pediatric hip claims go out with an unspecified code on them.

Keep pediatric hip documentation coding-ready

Pabau holds the assessment, the treatment note, and the diagnosis on one patient record, then pulls them into a pre-filled claim. Your team documents the affected side once and bills from it.

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Conclusion

Two decisions settle M91.91. Confirm the condition type is genuinely unspecified rather than LCPD, coxa plana, or another named entity. Then confirm the right leg is documented somewhere a payer can read it.

Get both right and M91.91 is the accurate, billable choice for FY2026. Get either wrong and the cost is a denial plus a records request, weeks after the child was treated. The cheapest place to fix that is the assessment template, long before the billing queue.

Software that carries the laterality note through to the claim takes the guesswork out of it. Book a demo to see how Pabau handles pediatric musculoskeletal documentation and billing.

Continue your research

Documenting a pediatric hip examination? Ober’s test walks through how to perform the assessment and record which side was tested.

Coding the hip pain alongside the diagnosis? M25.559 covers what to do when the note never names the affected side.

Tracking lower-limb function across visits? Star excursion balance test gives you a repeatable scoring method for the record.

Facing an unspecified-site code elsewhere in the M chapter? M66.9 shows how the same specificity rules play out for tendon rupture.

Coding a spinal presentation in the same caseload? M43.9 sets out the documentation a deforming dorsopathy claim needs.

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