Received: 26 March 2001
Revised: 14 June 2001
Accepted: 14 February 2002
Published online: 24 April 2002
© ISS 2002
Abstract Variable pathologies are
subsumed under the term “synovial
disease”, including common patholo-
gies such as rheumatoid arthritis.
While formerly radiologists had to
rely on conventional radiographs and
bone scintigraphy with their inherent
problems in visualizing soft tissue,
noninvasive imaging of the synovi-
um has recently improved substan-
tially with the technical development
of MRI and (Doppler) ultrasound.
These imaging modalities allow dif-
ferentiation of characteristic patho-
logic features based on a profound
knowledge of normal anatomy and
pathophysiology.
Keywords Inflammatory synovial
disease · Blastomatous synovial
disease · Rheumatoid arthritis · MRI ·
Doppler ultrasound
Skeletal Radiol (2002) 31:313–333
DOI 10.1007/s00256-002-0500-5
REVIEW ARTICLE
H. Imhof
I.-M. Nöbauer-Huhmann
A. Gahleitner
F. Kainberger
C. Krestan
I. Sulzbacher
S. Trattnig
Pathophysiology and imaging in inflammatory
and blastomatous synovial diseases
Anatomy and physiology
Most of the synovial joints are relatively mobile and
therefore inherently unstable. Stability is produced by
the capsule, ligaments and muscles. The capsule joins
the extremities of the bones and encloses the sealed ar-
ticular cavity which contains the synovial fluid – a color-
less, transparent, viscous fluid rich in hyaluronic acid
[1]. The capsule is composed of two layers: an external
fibrous layer and an internal synovial layer. Whereas the
first is a complex structure of collagen fibers with hardly
any metabolic activity, the synovial layer with its high
capillary content ensures a fast and extensive reaction to
any kind of agent. It is arranged in folds covered by one
or two layers of two types of lining cells. These cells are
either so-called A-cells derived from bone marrow and
capable of phagocytosis when presented with foreign
material, or B-cells which are special fibroblasts of mes-
enchymal origin that synthesize important proteins of the
synovial fluid such as glycosaminoglycans and hyaluro-
nate proteins, contributing to the lubrication of joint
structures (Fig. 1). No basal layer separates these lining
cells from the underlying synovial stroma, which con-
sists of a loose network of collagen fibers with many
vessels and varying amounts of fat cells (Fig. 2). These
vessels are the only intra-articular vessels. This facili-
tates the interchange between synovial fluid and vessels
[1].
The synovial fluid is a dialysate of plasma with a high
viscosity. It also contains cells, mostly phagocytes and
neutrophils. The fluid content of glucose, uric acid and
lactate is similar to that of plasma, but there is less total
protein. The low content of fibrinogen prevents clotting.
There is no complete cellular barrier between the fluid
and the more solid tissue. Thus, the only opposition to
free movement of chemical mediators and cells from one
tissue to the next is the physical (and chemical) charac-
teristics of the tissue matrices.
In some joints, such as the knee or the elbow, a partic-
ular part of the synovium is formed by incompletely re-
H. Imhof (
✉
) · I.-M. Nöbauer-Huhmann
A. Gahleitner · F. Kainberger · C. Krestan
S. Trattnig
Osteology,
Universitäts Klinik für Radiodiagnostik,
AKH Vienna, Wäehringer Guertel 18–20,
1090 Vienna, Austria
e-mail: mr@univie.ac.at
Tel.: +43-1-404005803
Fax: +43-1-404003777
I. Sulzbacher
Klinisches Institut für klinische Pathologie,
AKH Vienna, Vienna, Austria