Facet procedures rarely deny because the injection was wrong. They deny because it was the fifth diagnostic session in twelve months, the repeat ablation came too soon, or the relief scores never made it into the note.
Medicare’s Facet Joint Interventions for Pain Management LCD, in effect since May 2021, caps each procedure per spinal region over a rolling 12 months: four diagnostic medial branch block (MBB) or intra-articular (IA) sessions, four therapeutic IA sessions and two radiofrequency ablation (RFA) sessions. Those caps carry into 2026 unchanged, with one new RFA coding rule for the upper lumbar joints. Below, we walk through each limit, what qualifies a patient for the next procedure, and how to keep every session payable.
Facet Frequency Limits at a Glance
Every limit below applies per spinal region, per rolling 12 months, and assumes the documentation requirements are met (LCD L38773).
| Procedure | Codes | Qualifying response | Maximum per rolling 12 months |
|---|---|---|---|
| Diagnostic MBB or IA injection | 64490-64491, 64493-64494 | At least 80% relief of index pain | 4 diagnostic sessions |
| Therapeutic IA injection | 64490-64491, 64493-64494 | At least 50% relief or function gain for 3+ months to repeat | 4 therapeutic sessions |
| Radiofrequency ablation (RFA) | 64633-64636 | Two prior diagnostic MBBs at 80%+; repeat needs 50%+ for 6+ months | 2 RFA sessions |
A session is every facet procedure done on the same day, so an MBB and an RFA on one date count as one session.
Diagnostic Medial Branch Blocks: The 80% Gate
Diagnostic blocks decide everything that follows, so their limits are the ones to get right first.
- First block: must produce at least 80% relief of the primary (index) pain, recorded on a pain scale before and after.
- Confirmatory block: a second diagnostic block at the same level, usually at least two weeks later, also at 80% or better. Two positive blocks are required before RFA.
- Session cap: no more than four diagnostic sessions per region in a rolling 12 months.
- KX modifier: add KX to the diagnostic injection lines, usually only the two initial diagnostic injections. The billing article warns that unusual KX use can trigger focused medical review (A58364).
A block that falls short of 80% does not qualify the patient for RFA. Record the result anyway; it explains why the treatment plan changed.
Therapeutic Joint Injections: Repeat Coverage Rules
Therapeutic intra-articular (IA) injections are the exception path, not the default. Medicare covers them only for patients who are not RFA candidates.
- Before the first therapeutic injection: two diagnostic procedures with at least 80% relief each, plus a documented reason the patient cannot have RFA.
- Before each repeat: at least 50% consistent pain relief for at least three months, or at least 50% improvement in function compared with baseline.
- Session cap: no more than four therapeutic IA sessions per region in a rolling 12 months.
A frequent gap is the missing “why not RFA” statement. Without it, therapeutic IA claims fail medical necessity even when the relief numbers qualify. It is one of several documentation issues covered in our post on pain management billing mistakes.
Radiofrequency Ablation: Initial & Repeat Procedures
RFA has the strictest timing rule of the three procedures: a repeat must be earned by six months of documented relief.
- Initial RFA: only after two diagnostic medial branch blocks, each with at least 80% sustained relief.
- Repeat RFA: at least 50% consistent improvement lasting at least six months, or at least 50% functional improvement.
- Session cap: no more than two RFA sessions per region in a rolling 12 months.
- Thermal only: 64633-64636 describe thermal RF ablation. Chemical, pulsed or low-temperature RF denervation is reported with 64999, which the billing article treats as non-covered.
RFA codes are reported per joint, not per nerve: 64633 or 64635 for the first joint and 64634 or 64636 for each additional joint.
2026 update: for the T12-L1 and L1-L2 facet joints, use 64633 and 64636; for two-level ablation at those joints, 64636 is reported with 64633 instead of 64635 (Noridian billing article A58403, revision effective September 17, 2026). Check your own MAC’s billing article for the same change.
Rules for All 3: Levels, Modifiers & Rolling 12 Months
MBB, IA and RFA claims share the same level limits, diagnosis requirements and 12-month clock. Miss any of them and a session within its frequency limit still denies.
Level Limits per Session
One or two levels, unilateral or bilateral, are allowed per session in one spinal region. Third and additional level codes (64492, 64495) are non-covered and paid only on appeal with strong documentation. A bilateral injection at one level is still one level, billed with modifier 50 (or RT and LT on separate lines in an ASC). Our guide to modifier codes in medical billing explains the bilateral rules in more detail.
Diagnosis Codes That Support Coverage
Covered diagnoses for these codes are mainly spondylosis codes (M47.812-M47.817, M47.892-M47.897) and ankylosing hyperostosis codes (M48.12-M48.17). A general low back pain code alone does not support a facet procedure; see our post on low back pain ICD-10 M54 codes for where those codes fit.
Tracking the Rolling 12 Months
The window rolls from each date of service, not the calendar year, and it follows the patient across providers and sites. Before scheduling, check the patient’s facet history by region and procedure type, including sessions done elsewhere. Imaging guidance (fluoroscopy or CT) is required and included in these codes, and general anesthesia is not covered. For the full pain management code set, see our CPT, ICD-10 and HCPCS codes for pain management.
Count Sessions Before You Schedule Them
The takeaway is simple: count before you schedule. Every facet session draws from a fixed yearly allowance, so a quick look at the past 12 months of facet sessions for that patient, plus relief scores captured the same way after each block, prevents most denials before they happen. Payment follows the documentation, not the procedure.
If facet denials are already eating into your revenue, MBW RCM can help you put that check in place. Our pain management billing specialists review facet claims against the LCD and flag problems before the patient is booked.