2027 ICD-10-CM Diagnosis Code G90.521Complex regional pain syndrome I of right lower limb
ICD-10-CM Codes›G00–G99›G89-G99›G90
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Chronic Condition
G90.521 is a billable ICD-10-CM diagnosis code for complex regional pain syndrome I of right lower limb. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 73 through 74. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 156 closely related codes. Coders also document this condition as complex regional pain syndrome of lower limb. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system pain and pain syndromes.
G90.521 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 75 for payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
G90.521 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Complex regional pain syndrome of lower limb
- Complex regional pain syndrome type I
- Complex regional pain syndrome type I of right lower limb
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G90.521: its own notes plus those printed at G90.5, G90, and Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name G90.521, its category, or a range that includes it.
Excludes1 6
These codes carry an Excludes1 note naming G90.521: they are not reported together with it, unless the two conditions are unrelated.
- G56.4 Causalgia of upper limbcomplex regional pain syndrome I of lower limb (G90.52-) names G90.52-, which includes this code
- G56.4 Causalgia of upper limbreflex sympathetic dystrophy of lower limb (G90.52-) names G90.52-, which includes this code
- G57.7 Causalgia of lower limbcomplex regional pain syndrome I of lower limb (G90.52-) names G90.52-, which includes this code
- G57.7 Causalgia of lower limbreflex sympathetic dystrophy of lower limb (G90.52-) names G90.52-, which includes this code
- G89.2 Chronic pain, not elsewhere classifiedreflex sympathetic dystrophy (G90.5-) names G90.5-, which includes this code
- M89.0 Algoneurodystrophyreflex sympathetic dystrophy (G90.5-) names G90.5-, which includes this code
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Complex Regional Pain Syndrome I
a neurologic condition characterized by burning pain, tenderness, swelling, and changes in the skin color and temperature of a body part or extremity that has no identifiable nerve injury; most pediatric patients present with this form.
Patient EducationClinical
Complex Regional Pain Syndrome
Complex regional pain syndrome (CRPS) is a chronic pain condition. It causes intense pain, usually in the arms, hands, legs, or feet. It may happen after an injury, either to a nerve or to tissue in the affected area. Rest and time may only make it worse.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G90.521 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G90.521Overview
What is the ICD-10 code for complex regional pain syndrome I of right lower limb?
The ICD-10-CM code for complex regional pain syndrome I of right lower limb is G90.521 (sometimes written as G90521). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G90.521 (Complex regional pain syndrome I of lower limb) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report complex regional pain syndrome I of right lower limb on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G90.521 group to?
When complex regional pain syndrome I of right lower limb is the principal diagnosis on an inpatient stay, it groups to MS-DRG 74, 73, with relative weights from 1.0172 to 1.5773 depending on complications. Higher weights mean higher Medicare reimbursement.
Is G90.521 a CC or MCC?
CMS lists G90.521 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 156 closely related codes in its exclusion list.
Can G90.521 be reported with a code from G57.7?
Not as a rule. The Excludes1 note at G90.5, which applies to G90.521, lists "causalgia of lower limb (G57.7-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
Does G90.521 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage: G90.521 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 75 (Polyneuropathy).
