Lateral epicondylitis of the left elbow — an enthesopathy characterized by degenerative changes and pain at the origin of the extensor carpi radialis brevis (ECRB) tendon on the left lateral epicondyle, commonly called tennis elbow.

Documentation tips

What should appear in the chart to support M77.12.

Source · Editorial brief grounded in 6 cited references ↓

• Explicitly state 'left' elbow in the assessment — do not rely on laterality buried only in the HPI or examination section.
• Record the specific physical exam findings that confirm the diagnosis: point tenderness over the left lateral epicondyle, result of Cozen's test (resisted wrist extension with elbow extended), and any Mill's test or grip strength findings.
• If imaging was obtained, summarize the relevant finding — tendinosis at the ECRB origin on MRI or ultrasound, or calcification on plain X-ray — and link it to the left-sided diagnosis.
• Document the duration and character of symptoms, occupational or recreational risk factors (repetitive gripping, racquet sports), and any prior conservative care (bracing, NSAIDs, physical therapy) to support medical necessity for injections or surgery.
• For injection encounters, document the exact injection site ('left lateral epicondyle'), the injectate, and whether ultrasound guidance was used — this drives the CPT selection (20550 vs. 20551 vs. guided variant with 76942).

Related CPT procedures

Procedure codes commonly billed with M77.12. 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 M77.12 and adjacent codes.

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

• Defaulting to M77.10 (unspecified elbow) when the provider clearly documented 'left' — always assign the specific laterality code when it is in the record.
• Pairing M77.12 with a redundant elbow pain code (M25.522) once the definitive diagnosis is established — symptom codes are not reported separately when the underlying condition is confirmed.
• Miscoding left lateral epicondylitis as medial epicondylitis (M77.02) — confirm the epicondyle: lateral = outside of the elbow, medial = inside (golfer's elbow).
• Billing bilateral injections under a single M77.12 without also reporting M77.11 when both elbows are treated — each side requires its own laterality-specific code and the claim should reflect bilateral procedure billing accordingly.
• Failing to update from M77.10 to M77.12 at follow-up once laterality is documented — unspecified codes on repeat encounters are an audit flag.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M77.1 (laterality / anatomic variants).