Diagnostic imaging of arthrosis

General principles of radiograph interpretation

Analysis of conventional radiographs (CR) in joint pathology requires a strict systematic approach. The physician must sequentially evaluate several key radiological signs:

• Soft-tissue swelling (soft-tissue swelling): reflects effusion, synovial hypertrophy, or tissue edema itself.
• Joint space alteration: narrowing indicates cartilage destruction.
• Bone changes and osteopenia: assessment of periarticular bone density.
• Presence of erosions and enthesis involvement (enthesitis).
• Axis deviation and incongruity of joint surfaces.

The distribution pattern of the pathological process among various joints provides critically important information for differential diagnosis.

Basic radiological signs of osteoarthritis

Osteoarthritis most commonly affects major weight-bearing joints (knees, hips), as well as small joints of the hands, feet, and the spine. Conventional radiography reveals the following characteristic changes:

1. Non-uniform joint space narrowing (non-uniform alteration in joint space). Unlike inflammatory processes, cartilage degradation in osteoarthritis occurs locally in areas of highest mechanical stress. Exception: narrowing may be uniform in the small joints of the hands.
2. Osteophyte formation—marginal bone overgrowths that act as a compensatory reaction to joint instability.
3. Subchondral bone changes—development of osteosclerosis beneath the damaged cartilage.
4. Formation of intra-articular bodies and, in terminal stages, gross joint deformation with subluxation.

Erosive (inflammatory) osteoarthritis

Erosive osteoarthritis is a specific subgroup of the disease characterized by more pronounced inflammatory and destructive processes. It is significantly more common in women and carries a worse clinical prognosis compared to the classic non-erosive form.

• Localization: predominantly affects the distal (DIP) and proximal (PIP) interphalangeal joints of the hands.
• Specific signs: central erosions form in the subchondral bone zone. On radiographs, this creates the classic "seagull wing" sign (seagull wing). Marginal erosions are not characteristic of this form.
• Outcome: unlike conventional osteoarthritis, the erosive form may be accompanied by reparative changes that ultimately lead to the formation of true bony ankylosis (bony ankylosis).

Differential diagnosis

Imaging data reliably distinguish osteoarthritis from other joint pathologies:

• Inflammatory arthritides (e.g., rheumatoid arthritis): joint space narrowing is uniform. Marginal erosions are present, located on exposed bone between the cartilage and capsule. Periarticular osteopenia is characteristic.
• Gout (gout): the joint space remains preserved for a long time. Erosions have a juxta-articular location (further from the joint) and feature characteristic overhanging margins—the "punched-out" appearance (punched-out appearance). Soft-tissue swelling has an asymmetric, "lumpy" appearance.
• Diffuse idiopathic skeletal hyperostosis (DISH): this pathology reveals massive ossification of the spinal ligaments. The key difference from osteoarthritis (and spondylosis) is the relative preservation of intervertebral disc height at the affected levels.
• Secondary osteoarthritis in hemophilia: develops as a result of chronic hemarthrosis. In addition to joint space narrowing and subchondral cysts, specific signs such as widening of the intercondylar notch of the knee joint may be detected.

Role of cross-sectional methods (ultrasound and MRI)

Conventional radiography clearly demonstrates late, irreversible bone changes. Cross-sectional methods are used to detect early pathologies and soft-tissue abnormalities:

• Magnetic resonance imaging (MRI): has high sensitivity to subchondral zone changes. MRI allows visualization of bone marrow lesions (bone marrow lesion), which frequently accompany osteoarthritis (modern data show this is not true edema).
• Ultrasound (US): highly suitable for detecting a concomitant inflammatory component. Ultrasound easily visualizes anechoic effusion in joint recesses, hypertrophied synovium, and early osteophyte formation. The state of the menisci (e.g., their extrusion from the joint space) and the ligamentous apparatus can also be assessed.

Class and exam questions

What else to study on this topic

• Classification of bone tissue erosions: marginal, central, juxta-articular
• Radiological criteria for diffuse idiopathic skeletal hyperostosis (DISH)
• Bone marrow changes (bone marrow lesions) on MRI
• Radiological diagnostics of secondary osteoarthritis in hemophilic arthropathy
• Ultrasound assessment of effusion and synovitis in joint diseases

Other topics in the "Musculoskeletal System" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.