M01.X79 Direct infection of unspecified ankle and foot in infectious and parasitic diseases classified elsewhere

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from M01 Direct infections of joint in infectious and parasitic diseases classified elsewhere

Excludes1 (never code together)

• arthropathy in Lyme disease (A69.23)
• gonococcal arthritis (A54.42)
• meningococcal arthritis (A39.83)
• mumps arthritis (B26.85)
• postinfective arthropathy (M02.-)
• postmeningococcal arthritis (A39.84)
• reactive arthritis (M02.3)
• rubella arthritis (B06.82)
• sarcoidosis arthritis (D86.86)
• typhoid fever arthritis (A01.04)
• tuberculosis arthritis (A18.01-A18.02)

Code first

• underlying disease, such as:
• leprosy [Hansen's disease] (A30.-)
• mycoses (B35-B49)
• O'nyong-nyong fever (A92.1)
• paratyphoid fever (A01.1-A01.4)

Applies from M01.X7 Direct infection of ankle and foot in infectious and parasitic diseases classified elsewhere

Applicable to

• Direct infection of tarsus, metatarsus and phalanges in infectious and parasitic diseases classified elsewhere

Risk adjustment (HCC)

• CMS-HCC V28: HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
• CMS-HCC V22: HCC 39 — Bone/Joint/Muscle Infections/Necrosis
• ESRD V24: HCC 39

MS-DRG index

Defines the logic of DRG(s) 548-550 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 711.47 Arthropathy associated with other bacterial diseases, ankle and foot (approximate)
• 711.57 Arthropathy associated with other viral diseases, ankle and foot (approximate)
• 711.67 Arthropathy associated with mycoses, ankle and foot (approximate)
• 711.77 Arthropathy associated with helminthiasis, ankle and foot (approximate)
• 711.87 Arthropathy associated with other infectious and parasitic diseases, ankle and foot (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Manifestation codes as principal diagnosis: Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and are not allowed as principal diagnosis.
• Unspecified code (laterality): Unspecified codes for which a more specific code identifying laterality (right, left, bilateral) exists within the same code family.

Code annotations containing back-references to M01.X79

Back-references to M01

• Type 1 Excludes: M02 Postinfective and reactive arthropathies ("direct infections of joint in infectious and parasitic diseases classified elsewhere (M01.-)")

Nearby codes

• M01.X62 Direct infection of left knee in infectious and parasitic diseases classified elsewhere
• M01.X69 Direct infection of unspecified knee in infectious and parasitic diseases classified elsewhere
• M01.X7 Direct infection of ankle and foot in infectious and parasitic diseases classified elsewhere
• M01.X71 Direct infection of right ankle and foot in infectious and parasitic diseases classified elsewhere
• M01.X72 Direct infection of left ankle and foot in infectious and parasitic diseases classified elsewhere
• M01.X79 Direct infection of unspecified ankle and foot in infectious and parasitic diseases classified elsewhere (this code)
• M01.X8 Direct infection of vertebrae in infectious and parasitic diseases classified elsewhere
• M01.X9 Direct infection of multiple joints in infectious and parasitic diseases classified elsewhere