M77.11 classifies lateral epicondylitis — tendinopathy at the origin of the wrist extensor tendons on the lateral epicondyle of the humerus — specifically confirmed to the right elbow. Also documented as tennis elbow, right side.

Documentation tips

What should appear in the chart to support M77.11.

Source · Editorial brief grounded in 6 cited references ↓

• Record laterality explicitly — state 'right elbow' by name; do not rely on RT modifier alone to establish the diagnosis-level laterality.
• Document positive provocative tests by name (Cozen's test, Mill's test) to substantiate the lateral epicondyle as the pain source.
• If MRI or ultrasound was performed, note the specific finding (e.g., tendinosis at ECRB origin, partial tearing, tendon thickening) and the structure involved — this supports medical necessity for injections and advanced procedures.
• For injection claims using CPT 20550, document the specific tendon origin/insertion site injected, medication and dose administered, and laterality; add modifier RT to the CPT code.
• When conservative care has failed, document the duration and types of prior treatment (NSAIDs, physical therapy, bracing) — payers often require this history before approving corticosteroid injections or PRP.
• If both elbows are affected, code M77.11 and M77.12 separately; do not use M77.10 as a bilateral proxy.

Related CPT procedures

Procedure codes commonly billed with M77.11. 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 M77.11 and adjacent codes.

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

• Using non-billable parent code M77.1 instead of the laterality-specific M77.11 — M77.1 will reject on claims requiring a billable code.
• Confusing M77.11 (lateral epicondylitis, right) with M77.01 (medial epicondylitis, right) — they differ by one digit and represent anatomically distinct diagnoses on opposite sides of the elbow.
• Defaulting to M77.10 (unspecified elbow) when the note clearly documents the right side — this is a specificity downgrade that can trigger payer audits.
• Billing CPT 20551 for a tennis elbow injection when CPT guidelines direct use of 20550 for this indication — 20551 is for injection at a tendon origin/insertion, but the CPT manual specifically cites 20550 for tennis elbow injections.
• Omitting modifier RT on the CPT procedure code when M77.11 is the supporting diagnosis — mismatched laterality between the ICD-10 code and the CPT modifier is a common clean-claim failure.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

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