Inflammation of a bursa at the left knee, classified under soft tissue disorders linked to use, overuse, or pressure — excluding prepatellar bursitis, which has its own code (M70.42).

Documentation tips

What should appear in the chart to support M70.52.

Source · Editorial brief grounded in 5 cited references ↓

• Explicitly name the bursa involved (e.g., pes anserine, infrapatellar, medial collateral ligament bursa) to distinguish M70.52 from prepatellar bursitis (M70.42) and to support audit defense.
• Document the mechanism: repetitive kneeling, prolonged squatting, overuse in sport or occupation — language that ties to the M70 'use, overuse, and pressure' classification.
• Record left-sided laterality by name in the assessment and plan, not only in the HPI; laterality must appear in the diagnostic section to support the '2' sixth character.
• Include physical exam findings (bursal tenderness, swelling, warmth) and any imaging results (ultrasound or MRI confirming bursal distension or wall thickening) to establish medical necessity for injections or physical therapy.
• Document prior conservative treatment (NSAIDs, activity modification, physical therapy) if the encounter involves escalation to aspiration or injection, as payers require evidence of conservative care failure for many procedures.

Related CPT procedures

Procedure codes commonly billed with M70.52. 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 M70.52 and adjacent codes.

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

• Confusing M70.52 with M70.42 (prepatellar bursitis, left knee): if the documentation specifies prepatellar location, M70.42 is correct — M70.52 is for all other knee bursae.
• Defaulting to M70.50 (unspecified knee) when the left side is clearly documented — this triggers downcoding and payer queries.
• Applying M70.52 to an acute traumatic bursitis caused by a direct blow; M70 codes are for use/overuse/pressure etiologies, not acute trauma.
• Failing to pair M70.52 with an external cause code on workers' compensation claims, which can result in denial when the payer requires occupational etiology documentation.
• Using an incorrect sixth character: '2' = left, '1' = right, '0' = unspecified — transposing right and left is a frequent data-entry error that creates claim and audit problems.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Sibling codes

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