Altman, R. (1991). Classification of disease: Arthritis. Seminars in Arthritis and
Rheumatism, 20(6), 40-47.
A model for the classification of OA of several joints
Classification criteria is used to separate patients with specific disease from patients
without the disease. Sub classification criteria is used to separate diseases or
subsets within a disease cluster: primary/ idiopathic (unknown cause) and secondary
(known cause). Primary then divided into anatomical site, and secondary divided into
aetiology or associated condition or disease.
Criteria contain major characteristics, but not the entire spectrum of the disease
manifestations.
OA defined by: heterogenous group of conditions leading to the clinical syndrome of
joint symptoms and signs.
Arthroscopy makes it easy to diagnose, but can’t do this on every joint and its
impractical, so radiographs are often used, although cannot be used exclusively to
diagnose OA. This defines changes or articular cartilage and reactive changes in the
joint (effusions, osteophytes, and changes in subchondral bone). 40% of patients
with radiographic changes are not symptomatic, so they cannot be used to define
clinical OA.
Classification criteria help to improve understanding of elements used in diagnosis of
OA, enable physicians to use the same terms, provide a definition of OA that can be
critiqued, and improve diagnostic acuity of inexperienced physicians.
Criteria for OA of the Knee: knee pain with crepitus on active motion, morning
stiffness for <30 mins, >38 years
Although knee pain and radiographic osteophytes can occur independently, when
they occur together, its usually OA. Osteophytes best separate OA from other
diseases. Narrowing of the joint-space is not specific to OA, as it can occur with
patients with severely damaged menisci. With no pain and with radiographic
osteophytes, patients are not classified as having OA.
Criteria for OA of the Hand: symptoms bilateral, handedness isn’t a factor in severity.
Clinical examination is greater value than radiograph.
Higher prevalence of radiological erosions make it hard to distinguish inflammatory
arthritis from control group. One view of the hand makes it hard to see possible
dorsal or palmar osteophytes. Loss of soft tissue may give the appearance of bony
enlargement.
Study evaluated several physical findings, such as bony enlargement, swelling,
tenderness, and radiographic findings such as narrowing, osteophytes, deformity
Hard tissue: DIP or PIP joints with minimal or no MCP swelling. Involves at least 2
DIP joints.
Soft tissue: swelling of less than 3 MCP (excludes rheumatoid arthritis). RA and OA
can coexist in the hand. The presence of 3+ swollen MCP excludes most patients
with coexistent disease.
Criteria for OA of the Hip: Pain is the major symptom, but distribution is poorly
separated as the pattern distribution and activities with pain was very broad and
inconsistent. Clinical examination and radiograph is not superior to radiograph alone.
Two groups with painful hip OA:
1. ≤15° IR and erythrocyte sedimentation rate ≤45mm/h
2. >15°IR and morning hip stiffness ≤60min and >50 years
The osteophyte on the radiograph was the criteria that best separated hip OA from
control group when combining clinical and radiographic changes.
The clinical syndrome of OA can only be described. Until a 100% sensitive and
specific test for OA is found, descriptive criteria will be necessary.