ICD-10 Code for Chronic Left Knee Pain Explained

The problem of pain in the knees is one of the most widespread musculoskeletal complaints that can be observed during consultation in primary care, orthopedic surgery, sports medicine, physiotherapy, and pain management departments. Pain in the left knee, in turn, causes numerous claim submissions, and the ICD-10 diagnosis for left knee pain included in every billing encounter holds more value than people who create claims might expect. 

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The current guide provides information on all possible ICD-10-CM codes for left knee pain in the FY2026 Tabular List, specifies cases when their use is appropriate, shows the diagnoses that usually accompany left knee pain encounters, pays attention to the problems of chronic pain coding, and highlights documentation requirements and billing mistakes.

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How ICD-10-CM Organises Knee Pain Coding

ICD-10-CM codes for knee pain cannot be placed under a single heading. Depending on the case scenario, whether it is the primary diagnosis, whether there is an underlying structure involved, or whether it is the coding for chronic pain, codes for the same can lie within several chapters and codes.

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Chapters and Codes Relevant for Knee Pain Coding Include:

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• M25.56x: Pain in knee (laterality-specific symptom codes). It is used whenever the knee pain is the only primary finding noted during documentation without any other more specific structural injury.
• M17.x: Osteoarthritis of knee. It is employed when there is documentation of degenerative joint disease of the knee.
• M23.x: Internal Derangement of Knee. This includes knee problems involving torn menisci, cruciate ligament conditions, knee body problems, etc.
• G89.29 / G89.4: Chronic pain and chronic pain syndrome (Chapter 6: Diseases of the Nervous System). These codes are employed when chronic pain is documented by the physician.
• S80-S89 – Codes for knee and lower leg injury due to trauma such as fractures, sprains, and ligament tears.

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The proper primary code would be that of the structural disease itself when there has been a diagnosed structural disease like osteoarthritis, meniscus tear, or ligament tear. This code is used only when there has been no structural diagnosis.

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Core ICD-10 Codes for Left Knee Pain - FY2026 Reference

The following table covers the primary ICD-10-CM codes applicable to left knee pain presentations in outpatient, orthopaedic, and inpatient settings, verified against the FY2026 tabular list effective October 1, 2025.

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Left Knee Osteoarthritis Related Codes 

M25.562 - Pain in Left Knee

Code M25.562 is used in the case of pain in the left knee during evaluation, meaning that a specific diagnosis has not yet been made by the physician, or when the diagnosis that the patient has pain in their knee has been established but there is no structural pathology that causes it documented in the patient’s record. The code can be applied to many scenarios, but it is often incorrectly utilized despite a more specific code having been documented.

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Use M25.562 when:

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• When the patient comes for an initial consultation on the issue of pain in the left knee and no specific diagnosis has yet been determined.
• The imaging test results for the knee pain have not yet been acquired or analyzed in conjunction with diagnosing a problem.
• When the assessment of the patient’s condition documents only “left knee pain” with no specific condition causing it.
• To assess whether a diagnostic procedure such as MRI or surgery is medically necessary when no diagnosis has been established.

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Do not use M25.562 when:

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• The physician has indicated a definitive diagnosis such as "left knee osteoarthritis" (M17.12), "meniscal tear" (M23.2x2), or "patellar tendinopathy" (M76.52). The structural diagnosis code is the correct code, and M25.562 is not needed as well because using it is considered redundant.
• The pain is definitely due to an acute injury with the specified mechanism, for which you would use the injury code from Chapter 19.

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M17.12 – Unilateral Primary Osteoarthritis, Left Knee

When physicians document “Left knee OA,” “Degenerative joint disease left knee,” or “Left knee arthritis” during an exam or on imaging, then M17.12 would be the correct ICD-10 code for unilateral left knee pain due to such OA. Note that primary osteoarthritis is synonymous with idiopathic degenerative joint disease or arthritis where the OA develops as a result of wear-and-tear changes without an identifiable preceding injury leading to the OA.

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The M17.12 code can be used to justify medical necessity for:

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• Intra-articular corticosteroid injections (code 20610)
• Hyaluronic acid viscosupplementation injections (Examples include J7321–J7325)
• Physical therapy for left knee OA
• Total knee arthroplasty (TKA) after failure of conservative treatment
• Imaging studies for monitoring the disease, such as X-rays and MRIs

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M17.32 - Unilateral Post-Traumatic Osteoarthritis, Left Knee

While similar to the above M17.12, post-traumatic OA occurs after an identified documented injury to the joint (fracture, ligament tears, or joint dislocation), which injures the joint surface and hastens the development of degenerative changes in the joint. This scenario is common among trauma patients and athletes. The critical difference between these codes requires identifying and documenting the injury and attributing the OA to the injury.

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Guidelines on sequencing: Where the particular structural disease is documented (e.g., osteoarthritis of the left knee joint), M17.12 should generally be used as the principal code, while G89.29 can be the secondary code. When coding pain management, G89.29 should be considered for sequencing as the principal diagnosis depending on how this fits with ICD-10-CM criteria and insurance payer policies.

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It is important not to use G89.29 where G89.4 (Chronic pain syndrome) should be used instead. Chronic pain syndrome refers to a particular condition that is different from the mere presence of chronic pain. The physician should specify chronic pain syndrome to use G89.4.

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Documentation Requirements for Accurate Left Knee Pain Coding

The ICD-10 code used by your billing department for "left knee pain" depends on how specific the physician is in his documentation. Below are the required documentation criteria used in selecting the right code:

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• Laterality is specifically documented: It should read "left knee" and not simply "knee pain." Undocumented laterality uses a generic code of M25.569, which does not meet payer laterality edits where the procedure was done specifically on one side.
• Acuity: Acute vs. chronic. The time duration of the pain will affect coding and selection of the correct code. G89.29 may be additionally reported when chronic pain is specifically documented and clinically relevant to the encounter. However, "new onset left knee pain" will not justify the use of this additional code.
• Structural diagnosis is made or pending: When there is evidence from imaging that shows the diagnosis made for osteoarthritis, meniscus tear, etc., that code takes precedence rather than using the musculoskeletal pain code of M25.562. If the diagnosis is pending, the latter is used.
• Mechanism of injury: Where applicable, the cause of the knee injury/pain is required to be coded according to Chapter 19 codes and external cause codes.
• Activity limitation and effects on activity: The physician should document what activity limitations have been caused by the pain in the patient's left knee, including mobility, activities of daily living, work, and gait problems.

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Common ICD-10 Coding Errors for Left Knee Pain

• Error 1: Using M25.562 when a documented structural diagnosis is known. Since there is a structural diagnosis of left knee OA, code M17.12 should be assigned, not M25.562. Code the structural diagnosis over a symptom code since both are documented.
• Error 2: Assigning M25.569 (unspecified laterality) when left/right has been documented. Laterality information is usually provided in the clinical note; coding it as unspecified laterality when documentation is available can be considered an assignment error and could be rejected by the laterality edits linked to a procedure code.
• Error 3: Assigning M17.12 for bilateral knee osteoarthritis. Since the physician indicates that this is bilateral OA, assign code M17.2. M17.12 is specific for unilateral left knee OA.
• Error 4: Not using the correct 7th digit for injuries. Since the encounter is a follow-up encounter for the left knee injury, it cannot be coded with the "A" extension. The "D" extension should be applied during all follow-ups.
• Error 5: Assignment of G89.29 in absence of chronic pain documentation. Since this code requires documentation from the physician indicating "chronic pain," G89.29 is inappropriate in this case, even though the patient had left knee pain for one year.

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How RapidClaims Supports Accurate Left Knee Pain Coding

ICD-10 codes for left knee pain will determine the payment decision, pre-auth status, and medical necessity review results of each procedure included in the claim. With RapidClaims, accuracy of such decisions for each provider and each claim will be achieved consistently and reliably.

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RapidClaims enables the use of intelligent coding suggestions integrated into the claim creation process to verify each ICD-10 code based on the documentation provided, a tabular list for FY2026, and medical necessity guidelines of different payers. When coding left knee pain, RapidClaims allows you to:

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• Advise on use of more specific structural diagnosis codes like M17.12 or M23.x in cases where more specific condition documentation is present than unspecified knee pain coding
• Identify lack of laterality documentation and advise use of M25.562 in cases where left knee documentation is provided rather than unspecified knee coding
• Confirm accuracy of 7th character injury extensions and ensure that “A” is utilized for initial encounter codes and “D” for subsequent encounter codes
• Advise on Z96.652 coding for patients who have left total knee arthroplasty (TKA) documentation in their records
• Identify chronic pain coding cases by suggesting G89.29 when “chronic left knee pain” is documented
• Identify denials trend analysis for M25.562, M17.12, and other injury-related codes

Conclusion

The net effect of using this platform is that left knee pain claims are being properly coded based on the level of documentation provided by the physician – left knee, appropriate specificity, secondary codes, and first pass approval.

Coding the appropriate ICD-10-CM code for left knee pain will distinguish those claims from those that are going to get a denial, a query, or even be under-reimbursed due to inappropriate codes used – M25.562 for left knee pain, M17.12 for OA, M23.x for meniscal pathology, and G89.29 for chronic pain.

By the year 2026, the orthopaedic insurance payers will be increasingly focused on medical necessity and will look at the ICD-10 code for left knee pain on all claims very closely.

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FAQs

What is the ICD-10 code for pain in the left knee?

The ICD-10-CM code to use for left knee pain is M25.562 if the physician does not identify any other problem or structure causing the pain.

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What is the ICD-10 code for left knee pain, unspecified?

The code M25.562 is often assigned to unspecified left knee pain if there are only symptoms such as “pain in the left knee” but no diagnosis that identifies the underlying cause such as arthritis, torn ligament, etc.

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What is the ICD-10 code for left knee pain caused by osteoarthritis?

The proper ICD-10 code assignment is M17.12 if the physician has determined that the left knee pain is due to osteoarthritis.

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Can M25.562 be used together with structural knee diagnosis codes?

No, since the physician will usually provide documentation of an exact diagnosis of any structural damage or disease and not use terms such as pain to describe the left knee.

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When should coders avoid using M25.562 for left knee pain?

Coders need to refrain from using M25.562 when it is clear that there is another diagnosed condition or structural damage in the knee joint.