ICD code S83.015D – Lateral patellar dislocation of the left knee

Key takeaways

S83.015D is a billable ICD-10-CM code for lateral dislocation of the left patella at a subsequent (follow-up) encounter, valid for FY2026.

Use ‘D’ once active treatment ends and routine healing begins, never at the first ED or urgent care visit.

Recurrent patellar dislocation is typically coded from the M22.0- series, not S83.015D, which covers acute traumatic episodes only.

Practice management software like Pabau validates encounter type and laterality before the claim leaves your billing queue.

ICD-10 code S83.015D: Official descriptor and billable status

ICD-10 code S83.015D carries the official descriptor “Lateral dislocation of left patella, subsequent encounter”, as published in the CMS FY2026 ICD-10-CM Tabular List.

Most billing systems show the short descriptor, “Lat disloc left patella, subs.” The seventh character ‘D’ completes the code, so it is a valid leaf code and billable across all major payer types.

What is a lateral patellar dislocation?

A lateral patellar dislocation is the complete displacement of the kneecap from its groove in the femur. The patella shifts outward, toward the lateral side of the knee. Laterality matters twice over here. The left and right patellae have separate ICD-10-CM codes. Missing laterality in the note is also one of the most common reasons an S83.015D claim is denied.

The usual mechanisms are a planted foot with a rotational force, a direct blow to the inner side of the patella, or a non-contact pivot. Soccer and basketball produce plenty of the last kind. First-time dislocations are treated in an ED or urgent care setting and coded S83.015A. Follow-up visits are where S83.015D applies, whether that is the orthopedic review or the course of physical therapy.

• Acute presentation: sudden lateral shift of the kneecap, hemarthrosis, tenderness along the medial patellar retinaculum, positive apprehension sign
• Initial management: closed reduction, immobilization, and imaging where needed (X-ray or MRI to rule out osteochondral fracture)
• Subsequent encounters: brace fitting, physical therapy for quadriceps strengthening and VMO activation, a graded return-to-sport program
• Surgical cases: medial patellofemoral ligament (MPFL) reconstruction for recurrent instability, which changes the coding pathway (see the related codes section)

Why the seventh character ‘D’ decides the code

The seventh character in S83.015A, S83.015D and S83.015S sets the encounter type, not the severity of the injury. The ICD-10-CM Official Guidelines for Coding and Reporting (Section I.C.19.a) code active treatment as ‘A’. Once the patient is receiving routine care during healing or recovery, the correct character is ‘D’.

Here is the audit trigger. A patient dislocates the left patella at a soccer match on Monday, coded S83.015A, then attends a physical therapy assessment on Thursday. Billing S83.015A at that Thursday visit is compliant only if active reduction or acute management is happening.

For a functional assessment and exercise prescription, which is routine healing, S83.015D is the correct code. Misapplying ‘A’ at a therapy visit does more than invite a denial. It can flag the practice for a post-payment audit.

S83.015D and the codes it gets confused with

Several codes sit close enough to S83.015D to cause daily confusion. The table below maps the ones most often mixed up, across laterality, encounter type, subluxation versus dislocation, and recurrent-episode routing. When a neighbor looks closer to the note than S83.015D does, confirm it against the full ICD-10-CM code library before you submit.

Subluxation vs. dislocation: the distinction is clinical, and it must appear in the documentation. A subluxation is partial displacement, where the patella shifts but does not fully leave the trochlear groove. A dislocation is complete displacement.

If the note records “subluxation”, use S83.012D for a left-sided subsequent encounter. If it records “dislocation”, use S83.015D. Upgrading subluxation to dislocation without matching documentation is a compliance risk.

Recurrent vs. acute: where the patient has had several prior episodes and the provider documents recurrent patellar instability, the ICD-10-CM route is M22.02, not S83.015D. The S83 category is reserved for acute traumatic episodes.

Check the clinical record each time. A patient can sustain a new acute dislocation on top of a history of recurrence. In that case S83.015D still covers the acute episode, and M22.02 may be listed secondarily. The path from the note to the right code runs through three questions.

Excludes notes and instructional rules at category S83

Check the ICD-10-CM Tabular instructions at the S83 category level before you assign S83.015D. Two Excludes notes sit there, and they do different jobs.

Excludes1 at S83 covers birth trauma (P10-P15) and obstetric trauma (O70-O71). A knee injury from either cause is coded from those chapters, never from S83.

Excludes2 at S83 covers six conditions. An Excludes2 note means the condition is not part of S83, but both may be reported together when both are documented.

• Derangement of patella (M22.0-M22.3)
• Injury of patellar ligament or tendon (S76.1-)
• Internal derangement of knee (M23.-)
• Old or pathological dislocation of knee (M24.36)
• Recurrent dislocation of knee (M22.0)
• Strain of muscle, fascia and tendon at lower leg level (S86.-)

That fifth entry is why recurrent instability routes to M22.02 rather than S83.015D. M22.0 sits outside the S83 category by instruction, not by clinical judgment.

Two further instructions govern how the code is built and reported.

• Use additional code: pain documented as a separate clinical finding may take its own code, though straightforward subsequent encounters rarely need one.
• Seventh character required: every code in S83.01x needs one. A claim carrying “S83.015” alone is invalid and rejects at the clearinghouse or the payer edit.

Meniscal tears (S83.2-) and knee ligament sprains (S83.5-) are subcategories of S83 itself, not exclusions from it. They can be reported alongside S83.015D when each is separately documented. NCCI edits still apply at the procedure level, so check any CPT pair before submission.

Documentation requirements to support S83.015D

A claim carrying ICD-10 code S83.015D is read against the clinical documentation for four elements: laterality, directionality, injury type, and encounter context. Missing any one of them is grounds for a medical necessity denial.

• Laterality: the note must state “left” knee or “left” patella. “Bilateral” does not justify S83.015D, so use a separate code for each side. A right-knee note with a left-side code on the claim is among the fastest denial triggers.
• Directionality: the note should record a “lateral” dislocation. Many EHR templates default to “patellar dislocation” with no direction, so ask providers to specify lateral, medial or superior.
• Injury type: the provider records whether displacement was complete (dislocation) or partial (subluxation). Without that distinction, defaulting to dislocation is an assumption the documentation does not support.
• Encounter context: the note must read as a follow-up. Look for wording such as “continuing physical therapy” or “three weeks post-injury, recovering well”. Language describing active reduction, joint aspiration or closed manipulation signals an initial encounter instead.
• Prior initial encounter: the guidelines do not require the date of initial treatment in every subsequent note. Referencing the history of injury is still best practice, because post-payment reviewers look for a logical chronology.

Commonly paired CPT codes for subsequent encounters

ICD-10 code S83.015D pairs with evaluation and management or physical therapy procedure codes, depending on the setting. Practices handling a high volume of musculoskeletal follow-ups build these pairings into their billing templates. Software for billing teams can then flag an implausible CPT-ICD pair before the claim leaves the practice.

The pairings below cover most subsequent-encounter visits for a left patellar dislocation.

Confirm NCCI edits before submitting a CPT pair. Physical therapy CPT codes carry unit-per-day limits. Bundling rules can also apply when two timed codes, such as 97110 and 97140, fall on the same date.

Payer requirements and prior authorization

Requirements for subsequent patellar dislocation encounters vary by plan type. Authorization is one of the top reasons these claims sit unpaid, so check the rule before the visit rather than after the denial.

• Medicare: CMS requires documentation supporting the continued need for services. A physical therapy claim needs an active plan of care, and the therapy must be reasonable and necessary under the applicable Local Coverage Determinations. Statute caps no number of visits, though Medicare Advantage plans often impose their own limits.
• Commercial plans: many carriers require prior authorization for physical therapy beyond an initial block, commonly 6 to 12 visits. After that threshold, a functional progress note and re-authorization are needed. Without documented functional gains, continued therapy claims risk a medical necessity denial.
• Workers’ compensation: every submission needs the accepted claim number. Some states also mandate a physician referral for therapy under workers’ comp protocols. Jurisdiction-specific fee schedules govern the CPT reimbursement rate whatever the ICD-10 code.
• NCCI edits: the CMS National Correct Coding Initiative applies no edits at the ICD-10 level. Procedure-level edits on the CPT codes paired with S83.015D can still trigger automatic bundling denials, so check the current tables.

Common denial reasons, and how to prevent them

S83.015D claims come back for a predictable set of reasons. Most of the prevention work sits in the billing queue rather than the exam room.

A clearinghouse integration such as Claim.MD validates encounter-type and laterality fields before the claim reaches the payer. Steady denial management workflows then clear the ones that still come back, so the revenue cycle lag does not build.

• Wrong seventh character: submitting S83.015A at a follow-up therapy visit is the most common denial in this code family. Build a rule that flags ‘A’ codes when the encounter is documented as routine follow-up.
• Missing laterality: the claim codes left but the note says only “knee”. Require providers to select the side in the encounter template before sign-off.
• Dislocation coded as subluxation, or the reverse: the note records one and the billing team submits the other. Tie code selection to the provider’s documented diagnosis term, not to a generic patellar instability dropdown.
• Missing seventh character: a claim carrying “S83.015” alone is invalid and rejects at the front end. Configure the practice management system to require a complete seven-character code before the claim queues.
• Medical necessity at continued therapy: the payer decides the patient has plateaued. Have the treating therapist document measurable functional gains at each visit, such as KOOS scores or range-of-motion benchmarks, rather than attendance.
• Timely filing: claims submitted after the payer’s window, commonly 90 to 180 days from the date of service, are denied with no clinical appeal rights. Track date of service against submission date with automated alerts.

How Pabau keeps S83.015D claims clean before they leave the practice

A seventh-character error usually surfaces when the remittance advice arrives. By then the visit is weeks old, the coder has to reopen the note, and the appeal joins a queue nobody has time for.

Practice management software like Pabau keeps the coding decision next to the clinical record that justifies it. The treatment note, the laterality, the plan of care and the claim all sit on one patient record. Nobody reconciles two systems before submission.

Pabau’s claims management tools then check the claim before it goes out. Encounter type, laterality and CPT pairing are read against the note, and the clearinghouse integration catches the rest. Your team spends its week on patient care instead of reworking denials that were avoidable at the point of coding.

Stop losing revenue to seventh-character denials

Pabau’s claims management software validates encounter type, laterality and CPT pairs before submission. The Claim.MD clearinghouse integration catches what slips through, so your S83.015D claims reach payers clean.

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Conclusion

Three variables decide whether an S83.015D claim is right: the left side, a lateral dislocation rather than a subluxation, and a genuine subsequent encounter. Apply them consistently and the code stops being a denial source.

The seventh-character error is the one worth building a rule for. The difference between ‘A’ and ‘D’ looks small on the claim, and payers do not treat it as small. Put the check in the billing workflow, not in someone’s memory.

Pabau’s claims management software validates encounter-type logic and laterality at the point of claim generation. Book a demo to see how it handles musculoskeletal billing from the treatment note through to the remittance.

Continue your research

Want fewer S83.015D claims coming back? Clean claim explains what payers check before they pay, and which fields hold a claim up.

Want to understand the denial codes that come back on knee injury claims? Denial codes in medical billing decodes the CARC and RARC codes that accompany S83.015D rejections.

Need a plain-language overview of how clearinghouses work? Medical claims clearinghouse guide explains how electronic claim validation catches coding errors before payer submission.

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