Cartilage and bone damage in rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA), which is a chronic inflammatory disease with a multifactorial aetiology, leads to partial or permanent disability in the majority of patients. It is characterised by persistent synovitis and formation of pannus, i.e. invasive synovial tissue, which ultimately leads to destruction of the cartilage, subchondral bone, and soft tissues of the affected joint. Moreover, inflammatory infiltrates in the subchondral bone, which can lead to inflammatory cysts and later erosions, play an important role in the pathogenesis of RA. These inflammatory infiltrates can be seen in magnetic resonance imaging (MRI) as bone marrow oedema (BME). BME is observed in 68-75% of patients in early stages of RA and is considered a precursor of rapid disease progression. The clinical significance of synovitis and bone marrow oedema as precursors of erosions is well established in daily practice, and synovitis, BME, cysts, hyaline cartilage defects and bone erosions can be detected by ultrasonography (US) and MRI. A less explored subject is the inflammatory and destructive potential of intra- and extra-articular fat tissue, which can also be evaluated in US and MRI. Finally, according to certain hypotheses, hyaline cartilage damage may trigger synovitis and lead to irreversible joint damage, and MRI may be used for preclinical detection of cartilage biochemical abnormalities. This review discusses the pathomechanisms that lead to articular cartilage and bone damage in RA, including erosion precursors such as synovitis and osteitis and panniculitis, as well as the role of imaging techniques employed to detect early cartilage damage and bone erosions.

Keywords: cartilage; erosions; magnetic resonance imaging; rheumatoid arthritis; synovitis; ultrasound.

Fig. 1

Angiogenesis in the synovium of an rheumatoid arthritis patient with numerous proliferating vessels seen in hypertrophied villi. H&E, × 200.

Fig. 2

Inflammatory infiltrates in the adipose tissue. H&E, × 200.

Fig. 3

Ultrasound of the hand: metacarpophalangeal joints 2 joint synovitis, evident in both colour Doppler and low-velocity microvascular flow detection scan (left part of the image).

Fig. 4

Knee joint hyaline defect in a 17-year-old adolescent with juvenile idiopathic arthritis presenting with increased echogenicity of cartilage, despite smooth outline.

Fig. 5

Oedema of the prefemoral fat pad of the knee joint in a 64-year-old patient with rheumatoid arthritis. Thickened hypoechoic synovium is seen superficial to thickened fat tissue.

Fig. 6

Magnetic resonance imaging of the right elbow: axial PD (A), coronal T1 FS contrast medium (CM): effusions, significant thickening and post-contrast enhancement of the synovium seen as a lobulated, polycyclic mass, distending the capsule and penetrating between extensor and flexor muscles (B); cysts, hyaline cartilage loss in the lateral part and erosions in the medial part of the elbow joint.

Fig. 7

Magnetic resonance imaging of the knee in a 19-year-old man with RA: axial PD (A), axial T2 TIRM (B), axial T2 TIRM with overlapped T2 mapping (C), axial T2 mapping: focal chondromalacia on the lateral surface of the patella (D); yellow colour on T2 mapping indicates cartilage degeneration.

Fig. 8

Planar whole-body delayed-phase ^99mTc-MDP bone scan in the anterior and posterior projections in a 65-year-old woman with rheumatoid arthritis: increased uptake in the spine and multiple joints: right sternoclavicular, in multiple distal and proximal interphalangeal joints, metacarpophalangeal joints and right wrist, as well as left knee.