Recurrent subluxation of the left patella — repeated episodes of incomplete kneecap displacement from the trochlear groove, left side only, not caused by a single acute traumatic event.

Documentation tips

What should appear in the chart to support M22.12.

Source · Editorial brief grounded in 4 cited references ↓

• Specify left knee explicitly in the clinical note — laterality drives the 6th character (2 = left); 'knee pain' or 'patellar instability' without side documented forces M22.10 (unspecified).
• Document that episodes are recurrent: note the number of prior subluxation events, when they first began, and any triggering activities to distinguish this from an isolated first-time event.
• Record physical exam findings consistent with instability: positive patellar apprehension test, J-sign, medial patellofemoral ligament laxity, patellar tilt, or abnormal glide.
• Include relevant imaging findings — patellar height (Insall-Salvati ratio), trochlear dysplasia grade, tibial tuberosity–trochlear groove (TT-TG) distance, or MRI evidence of medial retinacular injury — to support medical necessity for conservative or surgical management.
• If conservative treatment has been attempted (bracing, PT, NSAIDs), document duration and response; payers commonly require this before authorizing surgical repair.

Related CPT procedures

Procedure codes commonly billed with M22.12. 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 M22.12 and adjacent codes.

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

• Using M22.12 for a first-time subluxation event — 'recurrent' is a clinical requirement; a single episode does not satisfy this code.
• Confusing M22.12 (recurrent subluxation) with M22.02 (recurrent dislocation, left knee) — subluxation is partial displacement; dislocation is complete. The provider's documented language should dictate which code is assigned.
• Applying M22.12 when the encounter is for an acute traumatic patellar dislocation — the Excludes2 note at M22 directs traumatic events to S83.0- with the appropriate 7th character.
• Assigning M22.10 (unspecified knee) when laterality is clearly documented in the note — this is an audit flag and may trigger a payer query or downcoding.
• Coding M22.12 alone when bilateral instability is documented — bilateral involvement requires M22.11 + M22.12; there is no standalone bilateral code in M22.1.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

Sibling codes

Other billable codes under M22.1 (laterality / anatomic variants).