ICD-10 code S52.209K: Forearm fracture with nonunion

Key Takeaways

ICD-10 code S52.209K describes an unspecified fracture of the shaft of the forearm, subsequent encounter for fracture with nonunion – it is a valid, billable ICD-10-CM diagnosis code.

The 7th character K specifically indicates a subsequent encounter where the fracture has failed to achieve expected union, distinguishing it from delayed healing (G) and malunion (P).

S52.209K is laterality-unspecified; if the affected side is documented, use laterality-specific sibling codes (S52.201K through S52.208K) for more precise reporting.

Pabau’s claims management software helps orthopaedic and physical therapy practices reduce claim errors by linking diagnosis codes to patient records and automating subsequent-encounter billing workflows.

Most forearm fracture claims get denied not because the injury is wrong – but because the encounter type and complication character are miscoded. ICD-10 Code S52.209K is the diagnosis code for an unspecified fracture of the shaft of the forearm, subsequent encounter for fracture with nonunion. It is a valid, billable ICD-10-CM diagnosis code accepted for claim submission under the current fiscal year tabular list maintained by the Centers for Medicare and Medicaid Services (CMS).

The code sits within ICD-10-CM category S52, which covers fractures of the radius and ulna. Nonunion is a clinically distinct complication: the fracture has failed to heal as expected after an appropriate healing period, rather than healing slowly (delayed healing, character G) or healing in a misaligned position (malunion, character P). Selecting the correct 7th character is the single most common source of claim errors for this code family.

S52.209K code details at a glance

The table below summarises the core reference data for this code as published in the ICD-10-CM tabular list.

Breaking down the S52.209K code structure

Each segment of ICD-10 Code S52.209K carries specific clinical meaning. Understanding the alphanumeric structure helps coders verify accuracy before submission and supports consistent ICD-10-CM diagnosis code selection across encounter types.

The digit 9 in position S52.209 signals laterality is unspecified. If the treating clinician has documented whether the fracture is on the right (1) or left (2) forearm, a laterality-specific code from the S52.201K-S52.208K range is more precise and may be required by certain payers.

Understanding the 7th character ‘K’ in ICD-10 code S52.209K

The 7th character is the most clinically sensitive part of any fracture code. For S52 codes, it distinguishes the treatment phase and the healing status of the fracture at the time of the encounter. Using the wrong 7th character is a leading cause of orthopaedic claim denials.

Per ICD-10-CM Official Guidelines Section I.C.19.c, character K applies when the fracture has definitively failed to unite. This is typically confirmed by imaging at a follow-up visit showing absence of bridging callus or a persistent fracture line beyond the expected healing window. The National Center for Health Statistics (NCHS) maintains these guidelines in coordination with CMS.

Clinical information: Forearm fracture nonunion

Nonunion of a forearm fracture is a recognised orthopaedic complication requiring separate clinical management from the initial fracture episode. Accurate patient records documenting the progression from initial injury to nonunion are essential for both clinical continuity and billing accuracy.

Common causes of forearm fracture nonunion:

• Inadequate immobilisation or premature weight-bearing after the initial fracture
• Distraction at the fracture site (excessive gap between bone fragments)
• Infection at or near the fracture site
• Poor vascular supply to the fracture zone
• Systemic factors including osteoporosis, smoking, diabetes, or nutritional deficiency
• Both-bones forearm fractures, where rotational forces complicate healing

Clinically, nonunion presents as persistent pain and functional limitation at the fracture site beyond the typical healing window (generally 6-9 months for forearm fractures, though this varies by patient and fracture type). Imaging findings confirming the diagnosis – absent bridging callus, sclerotic fracture margins, or medullary canal sealing – must be documented in the clinical record before applying character K per ICD-10-CM guidelines.

Includes, excludes, and applicable to notes

The S52 code block carries instructional notes that govern when S52.209K can and cannot be used. Understanding the Excludes1 and Excludes2 notes prevents unbundling errors and claim rejections from payers using the ICD List code editing database.

• Applicable to (S52 block): fracture of radius and ulna; includes both individual bone fractures and both-bones (combined) forearm fractures.
• Includes note: traumatic fractures of the forearm – S52.209K is intended for acute traumatic fractures and their sequelae, not pathological or stress fractures.
• Excludes1 (S52 block): fracture of wrist and hand (S62.-) – these are distinct anatomical regions and codes may NOT be reported with S52 codes for the same injury.
• Excludes2 (S52 block): periprosthetic fracture of radius (M97.3-) – if the fracture occurs around a prosthesis, a different code category applies and may be reported additionally when clinically appropriate.
• Note on physeal fractures: fractures of the upper end of the radius use S52.1 codes; fractures of the lower end use S52.5 codes. S52.2 (shaft) codes including S52.209K cover mid-diaphyseal fractures.

S52.209K in the ICD-10-CM code hierarchy

S52.209K sits at the end of a six-level code tree. Knowing the parent structure helps coders navigate the CDC/NCHS ICD-10-CM web tool and select the most specific applicable code. The hierarchy also connects to other ICD-10 diagnosis codes used in multi-condition encounters.

1. S00-T88 – Injury, poisoning, and certain other consequences of external causes
2. S50-S59 – Injuries to the elbow and forearm
3. S52 – Fracture of forearm
4. S52.2 – Fracture of shaft of radius
5. S52.20 – Unspecified fracture of shaft of radius
6. S52.209 – Unspecified fracture of shaft of unspecified forearm (parent, non-billable)
7. S52.209K – Subsequent encounter for fracture with nonunion (billable)

S52.209 (without the 7th character) is not billable. ICD-10-CM requires a complete code including the appropriate 7th character for all fracture codes in this block.

Related ICD-10-CM codes for S52.209K

The sibling codes below share the same parent (S52.209) but differ by 7th character, representing different healing outcomes. Coders at physical therapy practices managing fracture rehabilitation must select the correct encounter type at each follow-up visit. Verify current validity using the AAPC Codify ICD-10-CM lookup.

Documentation requirements for billing S52.209K

Billing S52.209K successfully requires more than selecting the right code. Payers – including Medicare and commercial insurers – apply medical necessity criteria that depend on what is documented in the clinical record at each subsequent encounter. Practices using claims management workflows should confirm these documentation elements are captured before submission.

• Confirmed nonunion diagnosis: The clinical note must state that nonunion has been confirmed, not merely suspected. “Concern for nonunion” does not support character K.
• Imaging findings: Radiology report or attending physician interpretation documenting absent bridging callus, persistent fracture gap, or medullary sclerosis.
• Treatment phase: The record should clarify this is a follow-up (subsequent) encounter, not an initial evaluation of a newly identified fracture.
• Laterality: If the treating clinician can confirm which forearm is affected, using a laterality-specific code (e.g. S52.201K for right, S52.202K for left) is preferable. When laterality is genuinely unknown or undocumented, S52.209K is appropriate.
• Cause of fracture / mechanism: Document the original mechanism of injury (traumatic fall, motor vehicle collision, etc.) to support medical necessity and distinguish the fracture from pathological or stress fracture categories, which have different code families.

The American Health Information Management Association (AHIMA) and the ICD-10-CM Official Guidelines for Coding and Reporting both emphasise that the physician or clinician of record is responsible for the diagnosis documented in the medical record. Coders assign the code that best represents that documented diagnosis – not a provisional or assumed one. Practices managing physiotherapy clinic compliance workflows should review their documentation standards for subsequent fracture encounters regularly.

Reduce claim errors on subsequent-encounter fracture codes

Pabau connects patient records, clinical notes, and billing workflows so your team has the documentation they need at every follow-up visit. See how orthopaedic and physical therapy practices use Pabau to streamline ICD-10-CM coding accuracy.

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How practice management software supports ICD-10 coding accuracy

Subsequent-encounter fracture coding is where claim errors compound. A patient with a forearm fracture nonunion typically attends multiple follow-up visits over several months, and the 7th character must be re-evaluated at each one. Practices managing this at volume – particularly physical therapy EMR users tracking rehabilitation progress – benefit from integrated coding workflows that surface the patient’s current fracture status at the point of care.

Key workflow improvements that reduce S52.209K coding errors include:

• Linked clinical documentation and billing: When the treating clinician’s note references imaging findings and confirms nonunion, that context should be visible to the coder at charge capture – not buried in a separate system. Pabau’s digital clinical forms keep structured assessment data tied to the patient’s billing record.
• Encounter-type tracking: Tracking whether the current visit is initial, routine subsequent, or complicated subsequent (nonunion, malunion) prevents teams from defaulting to character D when K or G applies.
• Audit trails for compliance: Practices subject to physical therapy regulatory requirements need documentation audit trails that show coding decisions are supported by clinical evidence at the time of the encounter.

Integrated practice management software that connects scheduling, clinical notes, and claim submission in one system reduces the gap between what is documented and what is billed. For a clinical coding resource, see the ResDAC guide to ICD codes in Medicare claims files, which covers how ICD-10-CM codes are captured and validated in claims data.

Conclusion

Forearm fracture nonunion is a clinically distinct and documentable complication – and ICD-10 Code S52.209K is the code that captures it. The difference between a paid claim and a denial often comes down to one character and one imaging report in the clinical record.

Pabau’s clinical compliance workflows connect patient documentation to billing at every subsequent encounter, reducing the 7th character errors that drive orthopaedic claim denials. To see how Pabau supports coding accuracy across your practice, book a demo.

Continue your research

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