General radiographic picture
On radiographs, progressive osteoarthritis manifests as a complex of structural bone changes. Soft tissue components and the cartilage itself are not visible on the images, so their condition is judged by indirect signs.
Classical radiographic manifestations include:
- Joint space narrowing, the size of which can decrease by 2–3 times relative to the norm.
- Formation of osteophytes — coarse bone outgrowths localized along the edges of the acetabulum/joint fossa.
- Pronounced deformation of articular surfaces.
- Appearance of subchondral sclerosis zones in the area of the epiphyses (bone compaction under the destroyed cartilage).
- Formation of bone cysts, which look like oval areas of radiolucency.
Pathogenetic consequence: Changes in limb statics against the background of osteoarthritis significantly increase the load on intervertebral discs, which accelerates their degeneration.
Stages of osteoarthritis according to N.S. Kosinskaya
The Russian school of diagnostic radiology traditionally relies on N.S. Kosinskaya's classification, which identifies three stages of the pathological process (in addition to a normal joint).
Stage III appears most prominently on images:
- The joint space almost completely disappears.
- Articulating surfaces are sharply widened due to massive marginal outgrowths and deformed.
- Against the background of general local osteoporosis, areas of gross sclerosis and cystic radiolucencies stand out.
- Calcifications in the periarticular tissues and so-called "joint mice" — loose intra-articular bodies — may be detected.
Clinically, this stage is accompanied by almost complete loss of mobility (only rocking movements remain), persistent contractures, instability, atrophy of the thigh and lower leg muscles, as well as severe pain. In gonarthrosis, a flexion contracture with varus deformity of the limb axis is formed. In bilateral coxarthrosis, the patient moves only on crutches, and the thigh moves together with the pelvis ("bound legs" syndrome).
Kellgren & Lawrence scale
In international practice, the Kellgren & Lawrence radiographic classification is more widely used, dividing the process into five stages:
- Stage 0: no pathological changes.
- Stage I (doubtful): minor, barely noticeable osteophytes are detected.
- Stage II (minimal): clearly defined, but single osteophytes are determined, joint space is minimally narrowed.
- Stage III (moderate): joint space is moderately narrowed, multiple osteophytes are visualized.
- Stage IV (severe): sharp narrowing of the joint space, accompanied by subchondral sclerosis and coarse, massive osteophytes.
Method limitations and alternatives
The main disadvantage of traditional radiography is the inability to visualize initial degenerative changes in the cartilage and surrounding soft tissues. Because of this, therapy often starts already at the stage of "organ failure," when tissues lose their ability to regenerate.
Other methods are used for a deeper assessment:
- MRI (magnetic resonance imaging): Evaluates cartilage, subchondral bone, menisci, and synovial membrane most accurately. Allows seeing the earliest structural defects before the appearance of radiographic markers. However, there is no universally accepted MRI classification yet, for gonarthrosis for example, and existing scales are used mainly for research purposes.
- Ultrasound: Helps assess the condition of the capsule, ligaments, menisci, identify radiolucent intra-articular bodies, and clarify the localization of cysts.
- CT (computed tomography): Unlike other methods, CT has proven uninformative for routine diagnosis of osteoarthritis.
JSN-O-S-C: Joint Space Narrowing, Osteophytes, Sclerosis, Cysts — the classical radiographic tetrad of progressive osteoarthritis.
Class and exam questions
Is it possible to see initial cartilage changes on a radiograph?
No, radiography does not visualize cartilage and soft tissues. MRI is necessary to detect early structural disorders.
What is a joint mouse?
This is a loose intra-articular body (cartilage or bone fragment) that can be found in the joint in the late stages of the disease.
Is pain a sign of changes on a radiograph?
Pain is the leading clinical symptom, increasing with exertion. However, the severity of pain does not always linearly correlate with the radiographic stage, especially at the beginning of the disease.
Is it necessary to perform a CT scan to confirm osteoarthritis?
No, computed tomography has not shown high informativeness for diagnosing this disease. Preference is given to radiography or MRI.
What else to study on this topic
- ICRS articular cartilage lesion classification (2003)
- Specific MRI signs of synovial membrane pathology
- Differential diagnostic radiology with septic arthritis
- Clinical picture and pain pattern in gonarthrosis
- Capabilities of arthroscopy in the objective assessment of articular cartilage
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