M91.31 identifies pseudocoxalgia affecting the right hip — a juvenile osteochondrosis condition grouped under M91.3, distinct from Legg-Calvé-Perthes disease and coxa plana despite overlapping clinical presentation in skeletally immature patients.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 7
- Region
- Hip
Documentation tips
What should appear in the chart to support M91.31.
Source · Editorial brief grounded in 4 cited references ↓
- Clinician must explicitly name the affected side — 'right hip' — in the assessment or impression; do not infer laterality from imaging orders or operative notes alone.
- Document the patient's skeletal maturity status (age, growth plate status on imaging) to support a juvenile osteochondrosis diagnosis rather than a degenerative or adult-onset condition.
- Record radiographic findings that support pseudocoxalgia — femoral head irregularity, joint space changes, or other osteochondrotic features — with imaging date and modality (X-ray, MRI).
- If conservative care has been initiated (activity restriction, physical therapy, non-weight-bearing), document it; this supports medical necessity for ongoing management visits.
- Clearly distinguish pseudocoxalgia from Legg-Calvé-Perthes disease, coxa plana, and SUFE in the clinical note — the diagnosis drives the code, and conflating terms causes coding errors.
Related CPT procedures
Procedure codes commonly billed with M91.31. 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 M91.31 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Coding M91.31 when documentation actually describes Legg-Calvé-Perthes disease (M91.11) — these are separate conditions with separate codes; confirm the clinician's stated diagnosis.
- Defaulting to M91.31 when laterality is not documented — use M91.30 (unspecified hip) until the record is amended to specify right.
- Reporting M91.31 alongside a slipped upper femoral epiphysis (nontraumatic) code from M93.0- — the M91 Excludes1 note prohibits this combination; recode to M93.0- if SUFE is the confirmed diagnosis.
- Using M91.31 for an adult patient without documented juvenile onset — if osteochondrosis occurred in adulthood or laterality/age context is unclear, review whether a different category applies.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
Pseudocoxalgia (M91.31) is a juvenile osteochondrosis of the right hip classified under the M91 category of juvenile osteochondroses of hip and pelvis. The condition produces hip pain, limping, and limited range of motion in children and adolescents, with radiographic findings that can mimic other osteochondroses. Use M91.31 when documentation clearly identifies the right hip as the affected side and the diagnosis is pseudocoxalgia specifically — not Legg-Calvé-Perthes (M91.11), coxa plana (M91.21), or coxa magna (M91.41), all of which have their own distinct codes within the M91 family.
Note the Excludes1 annotation at the M91 category level: slipped upper femoral epiphysis (nontraumatic), coded to M93.0-, cannot be reported alongside M91.31. These are mutually exclusive diagnoses; if the clinical picture shifts toward SUFE, recode entirely to the M93.0- subcategory. MS-DRG v43.0 groups M91.31 into DRG 553 (Bone diseases and arthropathies with MCC) or DRG 554 (without MCC), so accurate comorbidity documentation affects reimbursement tier.
If laterality is unspecified in the documentation, use M91.30 (unspecified hip) rather than defaulting to M91.31. If the left hip is affected, use M91.32. Never assume laterality from imaging orders alone — the clinician must document right hip explicitly in the assessment.
Sibling codes
Other billable codes under M91.3 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M91.31 (pseudocoxalgia) and M91.11 (Legg-Calvé-Perthes, right leg)?
02Can M91.31 be reported for an adult patient?
03Is there a 7th-character extension required for M91.31?
04What happens if the documentation does not specify right versus left hip?
05Can M91.31 be reported on the same claim as a slipped upper femoral epiphysis code?
06Which MS-DRGs does M91.31 map to?
07What imaging findings should be documented to support M91.31?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M91-M94/M91-/M91.31
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M91.31
- 04cms.govhttps://www.cms.gov/medicare/coordination-benefits-recovery/overview/icd-code-lists
Mira AI Scribe
The Mira AI Scribe captures the clinician's explicit statement of right-sided pseudocoxalgia, the patient's age and skeletal maturity, relevant imaging findings (femoral head irregularity, joint space, growth plate status), and any conservative treatment in place. This prevents laterality defaulting to M91.30 (unspecified), avoids conflation with Legg-Calvé-Perthes or SUFE, and ensures the record supports the correct MS-DRG tier if hospitalization or procedural coding follows.
See how Mira captures M91.31 documentation