Glossary · Anatomy

Rotator cuff

The rotator cuff is a group of four muscles and their tendons—supraspinatus, infraspinatus, teres minor, and subscapularis—that stabilize the glenohumeral joint and power shoulder rotation and elevation.

Verified May 8, 2026 · 6 sources ↓

Drawn from AAPCZimmerbiometCMSIcdcodesSprypt

Definition

Source · Editorial summary grounded in 6 cited references ↓

The rotator cuff encircles the humeral head like a cuff of tissue, holding it snugly against the glenoid fossa while allowing a wide arc of motion. The four muscles originate on the scapula and insert on the greater or lesser tuberosity of the humerus. The supraspinatus initiates abduction; the infraspinatus and teres minor externally rotate the arm; the subscapularis internally rotates it. Together they counterbalance the deltoid and prevent superior migration of the humeral head during overhead activity.

Tears are classified by cause—traumatic versus non-traumatic (degenerative)—and by extent: partial-thickness versus full-thickness (complete). Laterality matters at every step. A non-traumatic incomplete tear of the right shoulder codes to M75.111; a complete tear of the right shoulder codes to M75.121. Traumatic strains follow the S46.01x series instead. Surgical repair may be open or arthroscopic, acute or chronic, and those distinctions drive CPT code selection entirely.

From an imaging standpoint, MRI remains the standard for characterizing tear size, tendon retraction, and fatty infiltration of the muscle belly—all factors that affect surgical planning and, downstream, the complexity of the procedure code reported.

Why it matters

Failure to document laterality, tear extent (partial vs. complete), and traumatic mechanism before submitting a claim directly determines which ICD-10-CM code is billable. Reporting M75.100 (unspecified, no laterality) when the operative note clearly names the right shoulder is a specificity error that invites payer downcoding or denial. On the CPT side, selecting 23412 (open, chronic) versus 29827 (arthroscopic) versus 23420 (reconstruction with acromioplasty) changes reimbursement and Ambulatory Payment Classification assignment; mismatching the reported code to the documented approach or chronicity is among the most audited orthopedic coding errors.

Common mistakes

Where people most often go wrong with this concept.

Source · Editorial brief grounded in cited references ↓

Using M75.100 (unspecified shoulder, unspecified tear) when the operative or imaging report specifies laterality and tear completeness.
Reporting 23410 (open, acute) for a degenerative tear with no acute traumatic event—chronicity must be supported by clinical documentation.
Billing 23420 for a single-tendon repair; this reconstruction code requires documentation of a complete avulsion typically involving multiple tendons, not a routine repair.
Appending traumatic S46.01x codes for degenerative, non-traumatic tears—M75.11x and M75.12x are the correct series when no acute injury mechanism is documented.
Omitting laterality modifiers (RT/LT) or failing to match the side documented in the operative report to the side on the claim, creating a mismatch that triggers denial.
Assuming a single default ICD-10 code covers all rotator cuff scenarios; there is no LCD or NCD governing codes 23410, 23412, 23420, or 29827, so payers each set their own coverage criteria.

Related codes

Codes commonly involved when this concept appears in practice.

CPT

Modifiers

RT Right side LT Left side 59 Distinct procedural service 50 Bilateral procedure

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What is the difference between CPT 23412 and CPT 29827?

CPT 23412 describes an open repair of a chronic rotator cuff tear, while CPT 29827 describes the same repair performed arthroscopically. The arthroscopic code applies to both acute and chronic tears; the open codes split by acuity (23410 for acute, 23412 for chronic). Using the wrong code for the documented approach is a common audit finding.

02Which ICD-10 code should I use for a non-traumatic complete tear of the right rotator cuff?

Use M75.121 (Complete rotator cuff tear or rupture of right shoulder, not specified as traumatic). If laterality is unknown, M75.120 applies, but a more specific code should always be used when laterality is documented.

03When does a rotator cuff tear become traumatic for coding purposes?

A tear is coded as traumatic (S46.01x series) when the clinical record documents an acute injury event as the cause. Degenerative or insidious-onset tears without a documented acute mechanism are coded with M75.11x (incomplete) or M75.12x (complete), regardless of whether the patient reports prior shoulder activity.

04Is there an LCD or NCD that lists approved ICD-10 codes for rotator cuff repair?

No. As of the most recent guidance available, there are no Local Coverage Determinations or National Coverage Determinations specifically governing CPT codes 23410, 23412, 23420, or 29827. Payers set their own criteria, so coders should verify accepted diagnosis codes directly with each payer.

05What makes CPT 23420 different from the other rotator cuff repair codes?

CPT 23420 is a reconstruction code for a complete shoulder rotator cuff avulsion that is chronic in nature and includes an acromioplasty as part of the procedure. It is not appropriate for a standard single-tendon repair; documentation should reflect a more complex reconstruction—often involving multiple tendons—to support this code over 23412.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

When Mira detects rotator cuff pathology in a clinical note, it checks for four specificity elements before suggesting a diagnosis code: (1) laterality—right, left, or unspecified; (2) tear completeness—partial-thickness or full-thickness; (3) mechanism—traumatic (routes to S46.01x) versus non-traumatic/degenerative (routes to M75.11x or M75.12x); and (4) chronicity, which is required for CPT code selection on repair claims. If any element is absent from the note, Mira flags it for provider clarification rather than defaulting to an unspecified code. On the procedure side, Mira maps the operative approach and tear characteristics to the appropriate CPT: open-acute → 23410; open-chronic → 23412; reconstruction with acromioplasty → 23420; arthroscopic (acute or chronic) → 29827. Because no LCD or NCD governs these four CPT codes, Mira also surfaces the payer-specific coverage criteria on file and prompts the coder to confirm that the selected ICD-10 code aligns with the individual payer's accepted diagnosis list. Laterality modifiers RT and LT are auto-suggested based on the side documented in the operative report.

See Mira's approach

Related terms

Supraspinatus tendon Anatomy

The supraspinatus tendon is the distal fibrous attachment of the supraspinatus muscle, spanning from the supraspinous fossa of the scapula to the superior facet of the greater tubercle of the humerus. It is the most frequently torn component of the rotator cuff and anchors the muscle's role in initiating shoulder abduction.

Glenohumeral joint Anatomy

The glenohumeral joint is the ball-and-socket articulation between the humeral head and the glenoid fossa of the scapula—the primary joint of the shoulder complex. It is the most mobile, and consequently the least inherently stable, joint in the human body.