Prepatellar bursitis of the right knee — inflammation of the bursa sac situated directly anterior to the patella, attributed to use, overuse, or sustained pressure on the joint.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 6
- Region
- Knee
Documentation tips
What should appear in the chart to support M70.41.
Source · Editorial brief grounded in 4 cited references ↓
- Explicitly state 'right knee' in the assessment — 'prepatellar bursitis' alone maps to the unspecified code M70.40.
- Note the mechanism or contributing activity (e.g., prolonged kneeling, repetitive squatting) to support medical necessity and enable Y93 external cause coding for occupational cases.
- Record objective findings at the prepatellar bursa: anterior patellar swelling, fluctuance, warmth, and tenderness distinct from the joint line.
- If aspiration or injection is performed, document the specific bursa targeted (prepatellar) and the substance injected or volume aspirated to support CPT code selection.
- Document any conservative care already attempted (NSAIDs, activity modification, padding) when the encounter supports injection or surgical intervention — this strengthens medical necessity.
Related CPT procedures
Procedure codes commonly billed with M70.41. 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 M70.41 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M70.40 (unspecified knee) when the provider has clearly documented right-side involvement — always code to the highest specificity supported by documentation.
- Confusing prepatellar bursitis with infrapatellar (Hoffa's) or pes anserine bursitis — each has its own code path; the anatomic location of swelling must match the code selected.
- Coding M70.41 for septic (infectious) prepatellar bursitis — infectious bursitis requires a code from M71.0- (Abscess of bursa) or M71.1- (Other infective bursitis), not M70.4-.
- Omitting a Y93 external cause code when the clinical note documents an occupational or activity-specific cause — M70 category guidelines instruct use of an additional code to identify the causative activity.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
M70.41 is the correct code when the provider documents prepatellar bursitis with explicit right-side laterality. The prepatellar bursa sits between the skin and the anterior surface of the patella; when inflamed — typically from repetitive kneeling, direct trauma, or occupational pressure — it produces anterior knee swelling, tenderness, and warmth at the patella. Because M70 covers soft tissue disorders related to use, overuse, and pressure, the code carries an implicit occupational link. If the encounter note reflects an occupational origin, add an external cause code from Y93 to identify the activity causing the disorder.
Laterality is built into the 6th character: M70.41 = right, M70.42 = left, M70.40 = unspecified. Don't default to M70.40 if the provider documents a side — payers expect the specific code, and leaving laterality unspecified is a common audit trigger. Bilateral prepatellar bursitis cannot be coded with a single code; report M70.41 and M70.42 together.
Key excludes to know: M70 excludes bursitis NOS (M71.9-), bursitis of the shoulder (M75.5), and enthesopathies (M76–M77). Septic bursitis requires a different code path entirely. MS-DRG v43.0 groups M70.41 into DRG 557 (Tendonitis, myositis and bursitis with MCC) or DRG 558 (without MCC) for inpatient encounters.
Sibling codes
Other billable codes under M70.4 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M70.41 and M70.40?
02Can I use M70.41 for septic prepatellar bursitis?
03How do I code bilateral prepatellar bursitis?
04Should I add an external cause code when the bursitis is work-related?
05Which CPT codes are commonly paired with M70.41?
06What MS-DRG does M70.41 map to for inpatient encounters?
07Is M70.41 valid for the 2026 coding year?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
Mira AI Scribe
Mira's AI scribe captures laterality (right knee stated explicitly), the anatomic focus of swelling (anterior/prepatellar, not joint line), mechanism or occupational exposure, and any prior conservative treatment — preventing a downcode to M70.40 (unspecified) and flagging when a Y93 activity code should accompany the claim.
See how Mira captures M70.41 documentation