A flail joint at a site not covered by any other specific M25.2x subcategory — meaning the joint has lost all functional stability and moves passively beyond its normal range in every plane.

Documentation tips

What should appear in the chart to support M25.28.

Source · Editorial brief grounded in 5 cited references ↓

• Name the specific joint in the clinical note (e.g., 'flail acromioclavicular joint, left side') — M25.28 carries no laterality digit, so laterality must live in the documentation.
• Describe the mechanism or etiology: brachial plexus injury, ligamentous rupture, neuropathic destruction, post-surgical failure, etc. This supports medical necessity and any secondary diagnosis coding.
• Record objective findings that confirm flail status — passive range of motion exceeding normal anatomic limits in multiple planes, absence of active stabilization, and any imaging (stress X-ray, MRI) demonstrating structural incompetence.
• If the flail joint is a sequela of a prior trauma, document the original injury site, date, and relationship to the current presentation to support correct S-code sequela assignment alongside M25.28.
• Note any prior conservative or surgical treatment and its outcome; payers may require evidence that the instability is persistent and not an acute-phase finding.

Related CPT procedures

Procedure codes commonly billed with M25.28. 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 M25.28 and adjacent codes.

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

• Using M25.28 for knee, hip, elbow, wrist, hand, or ankle/foot flail joints — each of those sites has its own M25.2x subcategory and M25.28 is explicitly for 'other' sites not listed elsewhere.
• Confusing flail joint (M25.28) with joint instability (M25.3x) — instability implies abnormal movement within or slightly beyond normal limits; flail implies complete loss of all stabilizing control across all planes.
• Omitting the temporomandibular joint exclusion: TMJ disorders are excluded to M26.6x and must never be coded to M25.28 or any M25 subcategory.
• Failing to code the underlying etiology as an additional diagnosis — M25.28 describes the joint condition, not its cause; a separate code for neuropathic arthropathy, inflammatory disease, or injury sequela is typically required for complete claim adjudication.
• Applying M25.28 to a shoulder flail when the glenohumeral joint is intended — verify payer acceptance; some reviewers expect M25.21x (shoulder) even though that subcategory is not explicitly listed in all references, so confirm against the current tabular list.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Sibling codes

Other billable codes under M25.2 (laterality / anatomic variants).