ICD-10-CM · Hip

M16.4

Post-traumatic osteoarthritis affecting both hip joints simultaneously, arising as a direct consequence of prior trauma to each hip rather than from primary degeneration or dysplasia.

Verified May 8, 2026 · 6 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Hip

Drawn from CDCICD10DataCMSAAPCAhcc

Documentation tips

What should appear in the chart to support M16.4.

Source · Editorial brief grounded in 6 cited references ↓

Document the specific traumatic event for each hip (fracture type, dislocation, date of injury) that establishes the causal link to current OA — bilateral trauma must be explicit for both sides.
Record imaging findings for both hips: joint space narrowing, osteophytes, subchondral sclerosis, or Tönnis grade to support degenerative change consistent with post-traumatic etiology.
Note the timeline: when the original trauma occurred, prior treatments (ORIF, closed reduction, physical therapy), and progression to symptomatic OA — this chain of events is what separates M16.4 from M16.0.
If workers' compensation is involved, attach external cause codes for the mechanism and place of injury alongside M16.4; WC payers require this pairing.
Specify functional limitations (gait, weight-bearing status, activity restriction) to support E&M complexity level and medical necessity for any surgical or procedural claims.

Related CPT procedures

Procedure codes commonly billed with M16.4. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

27130 $1,162.02

Primary total hip arthroplasty replacing both the acetabular socket and proximal femoral components with prosthetic implants, with or without bone graft.

27132 $1,504.04

Conversion of a previously operated hip — any prior surgery except total hip arthroplasty — to a complete total hip arthroplasty, replacing both femoral and acetabular components, with or without bone graft.

27134 $1,695.43

Revision of total hip arthroplasty involving replacement of both the femoral and acetabular components in a single operative session.

27235 $836.36

Percutaneous skeletal fixation of a proximal femur fracture (femoral neck), performed with in situ pinning rather than open reduction.

27236 $1,089.87

Open treatment of a proximal femoral fracture at the femoral neck, using internal fixation hardware or prosthetic replacement to stabilize the fracture site.

27246 $427.87

Closed treatment of a greater trochanteric fracture without any reduction or repositioning of the bone fragments.

27253 $869.76

Open treatment of a traumatic hip dislocation without the use of internal fixation hardware

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

73502 $48.77

Radiologic exam of a single hip, capturing two or three views, including the pelvis when performed.

73521 $41.75

Bilateral hip X-ray examination capturing two radiographic views of both hips, including the pelvis when performed.

Common coding pitfalls

The recurring mistakes coders make with M16.4 and adjacent codes.

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

Assigning M16.4 when documentation only says 'history of hip trauma' without establishing that trauma caused the OA — correlation is not causation in the coder's eye or the auditor's.
Using M16.4 when only one hip has a documented traumatic etiology; the bilateral code requires a traumatic cause documented for both hips — code M16.51 or M16.52 for the affected side and the appropriate M16 code for the other.
Defaulting to M16.4 when the provider documents 'degenerative joint disease, both hips' without specifying post-traumatic etiology — unspecified bilateral hip OA maps to M16.0 or M16.9, not M16.4.
Confusing M16.4 (bilateral post-traumatic) with M16.6 (other bilateral secondary OA) — M16.6 is the correct code when the bilateral secondary OA etiology is something other than trauma (e.g., inflammatory, metabolic).
Failing to code the original injury or its sequela separately when clinically relevant for workers' compensation or personal injury cases — M16.4 alone does not capture the injury mechanism for those payers.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

M16.4 applies when documented osteoarthritis of both hips is causally linked to prior trauma — fractures, dislocations, acetabular injuries, or significant contusions — that preceded and precipitated the degenerative joint disease. The trauma history must be documented for both sides; if only one hip has a confirmed traumatic etiology, use M16.51 (right) or M16.52 (left) for that side. If the contralateral hip has a different etiology, code it separately with the appropriate M16 subcategory.

Post-traumatic hip OA sits within a precise classification hierarchy under M16. M16.0 covers bilateral primary OA (idiopathic), M16.2 covers bilateral dysplasia-related OA, and M16.6 covers other bilateral secondary OA. M16.4 is correct only when trauma is the documented cause for both hips — not aging, not dysplasia, not inflammatory arthritis. If the documentation says 'degenerative joint disease' without specifying etiology, default to M16.0 (bilateral primary) per Q4 2016 Coding Clinic guidance, not M16.4.

This code is frequently billed ahead of total hip arthroplasty (THA) on one or both sides, intra-articular injections, or physical therapy. Payers reviewing medical necessity for bilateral THA will scrutinize whether the documented trauma history is specific enough to justify M16.4 over a primary OA code. Workers' compensation carriers additionally require external cause codes alongside M16.4 to document the mechanism of the original injury.

Sibling codes

Other billable codes under M16 (laterality / anatomic variants).

M16.7

Other unilateral secondary osteoarthritis of hip

M16.9

Osteoarthritis of hip, unspecified

M16.6

Other bilateral secondary osteoarthritis of hip

M16.0

Bilateral primary osteoarthritis of hip

M16.2

Bilateral osteoarthritis resulting from hip dysplasia

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01What distinguishes M16.4 from M16.0?

M16.0 is bilateral primary (idiopathic) OA of the hip — no known cause. M16.4 requires documented prior trauma to both hips as the precipitating cause. If the provider doesn't specify etiology, default to M16.0 per Q4 2016 Coding Clinic guidance.

02Can I use M16.4 if only one hip has a traumatic cause?

No. If only one hip has a documented traumatic etiology, use M16.51 (right) or M16.52 (left). Code the other hip separately under the appropriate M16 subcategory matching its documented etiology.

03Do I need to code the original trauma separately when billing M16.4?

For standard commercial claims, M16.4 alone is typically sufficient for the OA diagnosis. For workers' compensation or personal injury cases, add external cause codes for the injury mechanism and place of injury — those payers require it.

04Is M16.4 valid for bilateral THA medical necessity?

Yes, M16.4 is an accepted primary diagnosis for total hip arthroplasty (CPT 27130) on one or both sides, provided the documentation clearly ties the post-traumatic etiology to each hip's degenerative changes. Imaging and functional impairment documentation strengthen the medical necessity case.

05What if the trauma history predates the current records — how do I document it?

The provider should document the traumatic history as reported by the patient, reference any available prior records (operative reports, radiology), and note imaging findings consistent with post-traumatic changes (e.g., prior fracture malunion, hardware artifacts). The clinical note connecting old trauma to current OA is what supports M16.4 under audit.

06How does M16.4 differ from M16.6?

M16.6 covers other bilateral secondary OA of the hip — etiologies other than trauma, such as inflammatory arthritis sequelae or metabolic causes. M16.4 is specifically for trauma-caused bilateral hip OA. Don't use M16.6 as a catch-all if trauma is the documented cause.

07Is a 7th character required for M16.4?

No. M-codes in the musculoskeletal chapter do not use 7th-character extensions. The 7th-character A/D/S convention applies to injury S-codes, not to M16.4.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira's AI scribe captures the traumatic event history for each hip (injury type, date, prior surgical or nonsurgical treatment), current imaging findings (joint space narrowing, osteophyte formation, Tönnis or Kellgren-Lawrence grade), bilateral symptom onset and progression, and current functional limitations. That documentation locks in M16.4 specificity, prevents a downcode to unspecified M16.9, and satisfies medical necessity requirements for bilateral arthroplasty or injection claims.

See how Mira captures M16.4 documentation