Radiology Coding Alert

Question: We have a patient who presents for a magnetic resonance imaging (MRI) scan of the right knee for chronic knee pain following an injury three weeks ago. The radiologist documents a tear of the articular cartilage within the knee joint in the impression without any other definitive findings. We coded this as S83.31XA and received a denial for medical necessity from the insurance company. Should we appeal?

Indiana Subscriber

Answer: Unfortunately, S83.31XA (Tear of articular cartilage of right knee, current, initial encounter) does not fall under the coding crosswalk for CPT^® code 73721.

When considering whether another diagnosis is applicable, you should check the ICD-10 guidelines. The 2018 ICD-10 guidelines state: "Codes that describe symptoms and signs, as opposed to diagnoses, are acceptable for reporting purposes when a related definitive diagnosis has not been established (confirmed) by the provider."

In this example, a definitive diagnosis has been established, so you should not resubmit with a different diagnosis, such as an unspecified injury of the knee. If, after checking your Local Coverage Determinations (LCDs) and confirming with the payer that the diagnosis code is not eligible for payment, you may consider an appeal since the claim was denied for medical necessity.

In your justification for the appeal, you should state that the patient presented for imaging due to an underlying injury, with the final diagnosis being a result of said injury. You may include information that explains how MRI imaging is vital in identifying injuries of the tendons, ligaments, and cartilage of the knee. You should also consider including a handwritten note from the provider explaining the medical necessity behind the procedure.

Caution: Some coders may consider submitting a generic knee injury code such as S89.91XA (Unspecified injury of right lower leg, initial encounter) or even S89.81XA (Other specified injuries of right lower leg, initial encounter) in place of S83.31XA. However, these would both be equally incorrect. While ICD-10 guidelines state that coders should apply the "causal" condition as the primary diagnosis, you should consider the tear of the articular cartilage to be the causal condition in this specific instance. That's because the articular cartilage tear is not the result of a knee injury, it is a knee injury. You should only consider a code such as S89.81XA when there is a clearly defined knee injury that cannot be classified under the ICD-10 index. If, for example, the provider documents "hyperextension of the cartilage within the knee joint," you could confidently apply code S89.81XA for lack of a better, more specified diagnosis code.