How to Properly Code Left Knee Pain with ICD-10: A Billing Guide
Left knee pain is one of the most common complaints seen in medical practices, from primary care and sports medicine to orthopedics and physical therapy. While the diagnosis may sound simple, coding it incorrectly can lead to denials, delayed reimbursement, and compliance risks.
This billing guide will walk you through how to correctly assign ICD-10 codes for left knee pain, covering common scenarios such as traumatic injuries, chronic conditions, and proper documentation requirements.
Table of Contents
Understanding the Basics of ICD-10-CM
The ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) is the standardized system used in the U.S. for coding diagnoses and inpatient procedures. Compared to ICD-9, ICD-10 provides much greater specificity, which is essential for accurate billing and reimbursement.
One important aspect of ICD-10 is laterality, meaning you must indicate whether the condition affects the left, right, or both sides. Also, many codes require indication of whether a condition is acute, chronic, or recurrent and what the underlying cause is (injury, arthritis, instability, etc.).
ICD-10 Code for General Knee Pain
A broad code for knee pain falls under Chapter 18: “Symptoms, Signs, and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified.”
M25.56 – Pain in joint, lower leg (general)
M25.562 – Pain in left knee (specific)
Using the detailed version (M25.562) when the documentation supports it helps avoid claim denials and ensures more precise data for your practice. For more insights, see our guide on what auditors look for in orthopedic coding
Coding Left Knee Pain from Traumatic Injury
When knee pain is due to a possible injury, such as a sprain, strain, dislocation, or fracture, ICD-10 codes from Chapter 19 come into play. Accurate documentation should include the type of injury, its severity, laterality, and whether it is an initial or subsequent encounter.
Examples include:
S83.91XA – Sprain of unspecified ligament of left knee, initial encounter
S82.122A – Displaced fracture of left tibial spine, initial encounter
The correct use of the 7th character (A / D / S) is critical for injury codes to reflect whether it’s initial, follow-up, or sequela. For more reference on specific knee pain coding, see the ICD-10 code details for left knee pain (M25.562).
Coding Left Knee Pain from Chronic Conditions
Chronic or non-traumatic causes of left knee pain are typically coded under Chapter 13, Diseases of the Musculoskeletal System. These might include osteoarthritis, tendonitis, bursitis, or meniscus issues when there's no recent injury. Examples:
Osteoarthritis: M17.12 – Primary osteoarthritis, left knee
Patellar tendinitis: M76.52 – Patellar tendinitis, left knee
Using Secondary Codes & Internal Audits
In many situations, one diagnosis code doesn’t fully capture the patient’s condition. For example, a patient may have a new injury superimposed on a chronic knee issue. In those cases, you might use:
A primary code for the acute injury (e.g. sprain)
A secondary code for the chronic pain (e.g. M25.562)
Also, to prevent coding errors and denials, internal reviews or audits are essential. If your practice doesn’t already have such a process, consider evaluating the Medical Coding and Audit Services offered by your RCM team. They can help catch inconsistencies, ensure documentation aligns with codes, and strengthen your audit readiness.
Documentation and Coding Guidelines
Provider documentation should clearly state: laterality (“left knee”), cause (injury, arthritis, etc.), whether the issue is acute or chronic, and whether the encounter is initial, subsequent, or a late effect (sequela). If the documentation lacks these details, payers often reject or demand supplemental information.
Avoid using nonspecific or unspecified codes (like M25.569) when the documentation actually provides more detail. For additional orthopedic-specific coding support, see our Orthopedic Surgery Coding Cheatsheet
Common Errors to Avoid
Some frequent pitfalls include mis-assigning laterality, using unspecified codes when specifics are known, misusing injury encounter characters, or failing to link the code to supporting documentation. These can all slow reimbursement, trigger audits, or cause denials.
Conclusion
Coding left knee pain correctly — using ICD-10 code M25.562 when documentation supports it — is more than just best practice. It’s essential for billing integrity, compliance, and ensuring your practice gets paid properly.
Including secondary condition codes, maintaining clean documentation, and performing internal coding audits (or accessing services like the Medical Coding and Audit Services) help safeguard your revenue cycle.
FAQs: Coding Left Knee Pain with ICD-10
- A = Initial encounter
- D = Subsequent encounter
- S = Sequela (late effect)
- Ensure provider documentation specifies laterality, cause, and encounter type.
- Use the most specific ICD-10 code available.
- Pair the diagnosis with the appropriate CPT code for procedures or imaging.
- Perform internal audits or use professional medical coding and audit services to catch errors before submission.
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