Purulent infection of a tendon sheath with abscess formation at a site not documented or specified in the clinical record.

Documentation tips

What should appear in the chart to support M65.00.

Source · Editorial brief grounded in 4 cited references ↓

• Document the specific anatomical site and laterality (e.g., 'right flexor tendon sheath of index finger') so a site-specific M65.0x code can replace M65.00.
• Add a secondary B95–B96 code to identify the bacterial agent whenever culture results or clinical suspicion of a specific organism (e.g., Staphylococcus aureus, Streptococcus) is documented.
• Record comorbidities such as diabetes mellitus or immunosuppression explicitly — these can qualify as MCCs and move the claim into MS-DRG 557 rather than 558.
• Distinguish whether the abscess arose from a current traumatic injury; if so, code the injury by body region instead of M65.00 per the Excludes1 note.
• Confirm the condition is not related to use, overuse, or pressure (which routes to M70.-) before assigning any M65.0 code.

Related CPT procedures

Procedure codes commonly billed with M65.00. 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 M65.00 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Defaulting to M65.00 when the chart clearly documents a side and region — always check for the site-specific child code (M65.011–M65.08x) first.
• Omitting the required secondary B95–B96 bacterial identification code, which is flagged during payer review and can delay or reduce payment.
• Assigning M65.00 for infections secondary to a documented current traumatic injury, which violates the Excludes1 note — code the injury instead.
• Confusing a septic tenosynovitis (inflammatory, not yet abscess-forming) with an abscess; abscess requires documentation of purulent collection, not just tenosynovitis signs.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Sibling codes

Other billable codes under M65.0 (laterality / anatomic variants).