Derangement vs. Tear
Internal derangement of the knee is a mechanical disorder of the knee which interferes with normal joint motion and/or mobility. A fragment of soft tissue or bone that suddenly becomes interposed between the articular surfaces is the classic cause of internal derangement. The misplaced fragment can be radiolucent or radiopaque. The most frequent cause of locking is entrapment of the radiolucent meniscus.
The most common IDK is the torn meniscus.
There are two principal cartilaginous structures in the knee joint - the articular cartilage and the menisci. The articular cartilage envelopes the bony ends of the tibia, femur and patella in contact with the joint. The menisci play a vital role in providing joint stability, impact absorption, and lubrication. Both of these structures can be acutely damaged by trauma or chronically damaged by cumulative joint trauma. Injury to the menisci generally results from traction, compression, torque forces, or a combination of all three.
The cruciate ligaments are most important in ensuring normal knee function. Damage to these ligaments contributes to significant impairment and disability. The anteriorcruciate ligament (ACL) is the more critical and is the most frequently involved in injury.
The complex interplay between instability, torn menisci, athletic activities, muscle control, and cumulative joint trauma ultimately leads to a degenerative change in the knee. It is often unclear what mechanism caused the disability, e.g. the original injury, repeated locking, instability, high athletic demands, powerful muscular contractions, repeated trauma or altered mechanics.
Osteochondritis dissecans of the femoral condyle is one of the most common conditions which generate radiopaque osteocartilaginous loose bodies. It is three times more common in men than in women. Osteochondritis dissecans of the patella, in some cases, appears to be due to a tangential or shear fracture secondary to subluxation. Persons with intra-articular loose bodies of the knee will develop degenerative arthritis. Time until presentation of arthritis is dependent, in part, on activity level, insofar as the more active the person, the earlier the onset of arthritis.
In ICD-9 CM there are 2 codes to choose:
717 â€“ Derangement (derangement MIGHT include a torn meniscus, but involves more than the meniscus, such as inclusion of the ligaments etc- Basically the knee is completely messed up inside, not just a simple torn meniscus). The 717 codes in general include â€śold meniscus tearsâ€ťâ€¦because clinically many patient suffer degenerative changes related to the surgery itselfâ€¦. So they can then DEVELOP a derangement later.
836.0 â€“ Tear of Medial Cartilage or meniscus of knee-,current. This is a simple meniscus tear. No other knee joint involvement and it is â€śnew or currentâ€ť.
Brian R. Boyce, CPC, CPC-I
Healthcare Operations, Regulatory Compliance & Coding Consultant