M25.569 — Pain in unspecified knee

Clinical Definition

Pain in the knee joint (gonalgia) is one of the most common musculoskeletal complaints encountered in primary care and orthopedic settings. ICD-10-CM code M25.569 specifically designates knee pain where the laterality — right or left — has not been specified in the clinical documentation. The knee is a complex hinge joint formed by the femur, tibia, and patella, and pain may originate from any of its structural components including articular cartilage, menisci, ligaments, bursae, tendons, or the synovial membrane.

Laterality is a fundamental coding principle in ICD-10-CM, and M25.569 exists as the unspecified-side option within the M25.56x subcategory. The laterality-specific codes — M25.561 (right knee) and M25.562 (left knee) — should always be used when the affected side is documented. The unspecified code M25.569 should only be reported when the medical record genuinely does not indicate which knee is painful, such as in incomplete referral documentation or when a patient reports bilateral knee pain that has not been further differentiated. Payers increasingly reject unspecified laterality codes, making accurate side documentation essential.

M25.569 is appropriate when knee pain is the primary clinical finding and a more definitive diagnosis (such as osteoarthritis, internal derangement, or ligamentous injury) has not yet been established. It captures the symptom of knee pain rather than an underlying pathology. Once diagnostic workup — including imaging, laboratory testing, or arthroscopic evaluation — identifies a specific structural or systemic cause, the code should be replaced with the corresponding diagnosis code. This code is commonly used at initial encounters, in urgent care settings, or when a patient presents with acute knee pain of unclear etiology pending further investigation.

When to Use M25.569

• ✓The patient presents with knee pain and the medical record does not specify whether the right or left knee is affected, making laterality-specific codes M25.561 or M25.562 inapplicable.
• ✓Initial encounter for knee pain of unclear etiology before a definitive structural or pathologic diagnosis (such as meniscal tear, osteoarthritis, or ligament injury) has been established through imaging or examination.
• ✓The patient reports diffuse or alternating bilateral knee pain and the documentation does not differentiate between the two sides for the purpose of the current encounter.
• ✓Urgent care or emergency department visit for acute knee pain where the clinical documentation is limited and does not include laterality, pending follow-up with an orthopedic specialist.
• ✓Referral documentation or external records indicate knee pain without specifying the affected side, and the receiving provider has not yet examined the patient to determine laterality.
• ✓Use as a secondary diagnosis to capture knee pain as a symptom when the primary diagnosis addresses a systemic condition (e.g., obesity, gout) that contributes to knee pain but laterality was not separately documented.

Common Coding Mistakes

Related & Differential Codes

Documentation Requirements

• 1Specify the laterality of the affected knee (right, left, or bilateral). This is the single most important documentation element for knee pain coding. Without laterality, the unspecified code M25.569 must be used, which may result in claim denials or reduced reimbursement.
• 2Document the onset, duration, and character of the knee pain (acute vs. chronic, constant vs. intermittent, sharp vs. aching, weight-bearing vs. at rest) to establish medical necessity for diagnostic workup and treatment.
• 3Record the physical examination findings including range of motion measurements, joint stability testing (Lachman, McMurray, varus/valgus stress), presence of effusion or crepitus, and any tenderness localization (medial, lateral, anterior, posterior).
• 4Include relevant patient history such as prior knee injuries, surgeries, or injections; occupational or recreational activities that may contribute to knee pain; and comorbid conditions (obesity, diabetes, gout) that affect treatment planning.
• 5Document any imaging results (X-ray, MRI, ultrasound) obtained to evaluate the knee pain, including specific findings such as joint space narrowing, meniscal tears, ligament integrity, or effusion.
• 6Note the functional impact of the knee pain on the patient's daily activities, gait, and mobility to support medical necessity for interventions such as physical therapy, bracing, injections, or surgical referral.
• 7If the knee pain is associated with a systemic condition (rheumatoid arthritis, gout, psoriatic arthritis), document the underlying diagnosis separately so the knee pain can be coded as a manifestation rather than an isolated symptom.
• 8Record the treatment plan including medications prescribed, physical therapy referrals, activity modifications, and any planned follow-up imaging or specialist consultation.

Reimbursement & Billing Notes

M25.569 is a valid, billable ICD-10-CM code accepted for claims submission across all major payers. It supports medical necessity for office visits, diagnostic imaging (knee X-rays, MRI when clinically indicated), physical therapy, durable medical equipment such as knee braces, and referrals to orthopedic specialists. However, because it is an unspecified laterality code, some payers — particularly Medicare Advantage plans and commercial insurers with quality-based reimbursement models — may flag or deny claims that use M25.569 when laterality could reasonably have been documented.

For optimal reimbursement, providers should use the laterality-specific codes M25.561 (right knee) or M25.562 (left knee) whenever possible. If M25.569 is used at an initial visit, it should be updated to a more specific code (either laterality-specific knee pain or a definitive diagnosis such as M17.x for osteoarthritis) at subsequent visits once additional clinical information is available. Prior authorization for advanced imaging (MRI) or interventional procedures (corticosteroid injections, viscosupplementation) typically requires a specific diagnosis rather than a symptom code; M25.569 alone may be insufficient for authorization of these services. Pairing M25.569 with supporting secondary diagnoses such as E66.01 (morbid obesity) or M17.9 (knee osteoarthritis) can strengthen the clinical justification when the symptom code is used.

Frequently Asked Questions