M70.51 identifies bursitis of the right knee involving a bursa other than the prepatellar bursa, typically arising from occupational use, overuse, or repetitive pressure on the joint.

Documentation tips

What should appear in the chart to support M70.51.

Source · Editorial brief grounded in 6 cited references ↓

• Explicitly document 'right knee' — laterality is required to bill M70.51 over the unspecified M70.50.
• Identify the specific bursa involved (e.g., pes anserine, infrapatellar, semimembranosus) to distinguish M70.51 from prepatellar bursitis (M70.41).
• Note whether bursitis is occupational or activity-related, and append a Y93.- external cause activity code per the M70 tabular instruction.
• Record imaging findings (ultrasound or MRI confirmation of bursal fluid/thickening) to support medical necessity for injection or aspiration procedures.
• Document failure or inadequacy of conservative management (rest, NSAIDs, physical therapy) when pursuing procedural intervention to satisfy payer LCD requirements.
• For infectious bursitis, shift to M71.161 — document culture results or clinical indicators of infection to justify the code change.

Related CPT procedures

Procedure codes commonly billed with M70.51. 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 M70.51 and adjacent codes.

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

• Using M70.51 for prepatellar bursitis — that bursa has a dedicated code (M70.41); M70.51 covers all other right knee bursae.
• Defaulting to unspecified M70.50 when the operative or clinical note clearly states 'right knee,' causing avoidable specificity downcoding.
• Omitting the Y93.- activity code when the note documents an occupational or sport-related mechanism, leaving the claim incomplete per tabular instructions.
• Coding M70.51 for infectious right knee bursitis — infected bursae belong in the M71.1- category (M71.161 for right knee).
• Billing M70.51 alone on a 20610 claim without verifying the payer's active LCD; Aetna/Coventry Medicare has previously denied 20610 claims citing no valid LCD even with a covered bursitis diagnosis.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M70.5 (laterality / anatomic variants).