2026 ICD-10-CM Diagnosis Code S80.221ABlister (nonthermal), right knee, initial encounter
S80.221A is a billable ICD-10-CM diagnosis code for blister (nonthermal), right knee, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 606 through 607, 963 through 965. Coders also document this condition as right knee blister with infection. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Superficial injury; contusion, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Right knee blister with infection
- Right knee superficial injury of skin
- Traumatic blister of knee
- Traumatic blister of right knee
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Superficial injury of knee and lower leg (S80). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Blisters
Blisters are fluid-filled sacs on the outer layer of your skin. They form because of rubbing, heat, or diseases of the skin. They are most common on your hands and feet.
The full article covers:
- What are blisters?
- What causes blisters?
- What are the treatments for blisters?
- Can blisters be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S80.221A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S80.221AOverview
Is S80.221A (Blister (nonthermal), right knee) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report blister (nonthermal), right knee, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S80.221A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for blister (nonthermal), right knee, such as an emergency visit or first evaluation.
What MS-DRG does S80.221A group to?
When blister (nonthermal), right knee, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, 963, 964, 965, with relative weights from 0.9064 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of S80.221A?
Under the General Equivalence Mappings, blister (nonthermal), right knee, initial encounter converts to ICD-9-CM 916.2 (blister hip & leg). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
