2026 ICD-10-CM Diagnosis Code M79.4
Hypertrophy of (infrapatellar) fat pad
- ICD-10-CM Code:
- M79.4
- ICD-10 Code for:
- Hypertrophy of (infrapatellar) fat pad
- Is Billable?
- Yes - Valid for Submission
- Chronic Condition Indicator: [1]
- Not chronic
- Code Navigator:
M79.4 is a billable diagnosis code used to specify a medical diagnosis of hypertrophy of (infrapatellar) fat pad. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026.
Approximate Synonyms
The following list of clinical terms are approximate synonyms, alternative descriptions, or common phrases that might be used by patients, healthcare providers, or medical coders to describe the same condition. These synonyms and related diagnosis terms are often used when searching for an ICD-10 code, especially when the exact medical terminology is unclear. Whether you're looking for lay terms, similar diagnosis names, or common language alternatives, this list can help guide you to the correct ICD-10 classification.
- Bilateral hypertrophy of infrapatellar fat pads
- Hypertrophy of fat pad of knee
- Hypertrophy of fat pad of left knee
- Hypertrophy of fat pad of right knee
Clinical Classification
Clinical Classifications group individual ICD-10-CM diagnosis codes into broader, clinically meaningful categories. These categories help simplify complex data by organizing related conditions under common clinical themes.
They are especially useful for data analysis, reporting, and clinical decision-making. Even when diagnosis codes differ, similar conditions can be grouped together based on their clinical relevance. Each category is assigned a unique CCSR code that represents a specific clinical concept, often tied to a body system or medical specialty.
Other specified connective tissue disease
CCSR Code: MUS025
Inpatient Default: Y - Yes, default inpatient assignment for principal diagnosis or first-listed diagnosis.
Outpatient Default: Y - Yes, default outpatient assignment for principal diagnosis or first-listed diagnosis.
Index to Diseases and Injuries References
The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).
- infrapatellar fat pad - M79.4
- popliteal fat pad - M79.4
- Fat
- localized (pad) - E65
- knee - M79.4
- retropatellar - M79.4
- knee - M79.4
- infrapatellar fat pad - M79.4
- popliteal fat pad - M79.4
Index of External Cause of Injuries
References found for this diagnosis code in the External Cause of Injuries Index:
- Degeneration, degenerative
- infrapatellar fat pad
- Degeneration, degenerative
- popliteal fat pad
- Fat
- localized (pad)
- knee
- Fat
- localized (pad)
- retropatellar
- Fat
- pad
- knee
- Fibrosis, fibrotic
- infrapatellar fat pad
- Fibrosis, fibrotic
- popliteal fat pad
- Hypertrophy, hypertrophic
- fat pad
- knee (infrapatellar) (popliteal) (prepatellar) (retropatellar)
Convert M79.4 to ICD-9-CM
Below are the ICD-9 codes that most closely match this ICD-10 code, based on the General Equivalence Mappings (GEMs). This ICD-10 to ICD-9 crosswalk tool is helpful for coders who need to reference legacy diagnosis codes for audits, historical claims, or approximate code comparisons.
Hypertrophy of fat pad
ICD-9-CM: 729.31
This is a direct match with no additional mapping qualifiers. The absence of a flag generally means the mapping is considered exact or precise. In other words, the ICD-10 code maps cleanly to the ICD-9 code without qualification, approximation, or needing multiple codes.
Patient Education
Knee Injuries and Disorders
Your knee joint is made up of bone, cartilage, ligaments and fluid. Muscles and tendons help the knee joint move. When any of these structures is hurt or diseased, you have knee problems. Knee problems can cause pain and difficulty walking.
Knee problems are very common, and they occur in people of all ages. Knee problems can interfere with many things, from participation in sports to simply getting up from a chair and walking. This can have a big impact on your life.
The most common disease affecting the knee is osteoarthritis. The cartilage in the knee gradually wears away, causing pain and swelling.
Injuries to ligaments and tendons also cause knee problems. A common injury is to the anterior cruciate ligament (ACL). You usually injure your ACL by a sudden twisting motion. ACL and other knee injuries are common sports injuries.
Treatment of knee problems depends on the cause. In some cases your doctor may recommend knee replacement.
NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases
[Learn More in MedlinePlus]
Code History
- FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026
- FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025
- FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
- FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
- FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
- FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
- FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
- FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
- FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
- FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
- FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.
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.
