Karantanas_edit.qxp 2/5/07 11:42 am Page 37
Imaging
Magnetic Resonance Imaging Findings in Early Osteoarthritis of the Knee
a report by
Apostolos H Karantanas
President Elect, European Society of Musculoskeletal Radiology
Osteoarthritis (OA) affects about 10% of adults over the age of 50 and cysts are considered findings of advanced disease regardless of
up to 70% of the population over the age of 65.
1
OA is a major cause whether the patients experience symptoms.
7
A knee is considered
of pain and physical disability associated with significant social and symptomatic if the patient states that he or she has pain or aching in
economical burden.
2
OA of the knee joint is one of the most common that knee on most days.
8
Early OA, according to two widely used
locations and is demonstrated with significant dysfunction.
3
Apart staging systems, is defined if in symptomatic patients there is,
from ageing, OA of the knee is associated with obesity, previous radiologically, joint space width of <3mm or if there are only minute
trauma, overuse in elite-level sports activities and genetic osteophytes.
9,10
Indeed, osteophyte formation is the most typical
predisposition. Therefore, OA probably represents a heterogenous feature of OA, is thought to precede JSN and is the most common
group of conditions resulting in similar pathological, radiological and finding in patients with early OA.
11
Moreover, the radiological
clinical features. The cause of pain in patients with knee OA remains appearance of osteophytes perhaps more accurately predicts knee
pain than JSN.
12,13
There are cases, though, where plain radiographs
are completely normal (see Figure 1). A substantial discordance
appears to exist between radiographic OA of the knee, knee pain and
The major limitations of plain
the clinical diagnosis of OA.
14–16
radiographs are related to
The major limitations of plain radiographs are related to
standardisation of the technique standardisation of the technique and the moderate accuracy and
and the moderate accuracy and
reproducibility for assessing joint space width. If used alone, plain
radiographs will miss a substantial proportion of cases with cartilage
reproducibility for assessing joint
loss in the knee joint.
17
One of the causes of inaccuracies for
space width.
assessment of the joint space is related to changes in the position and
degeneration of the meniscus (see Figure 1).
18
Others show significant
but moderate association between changes in JSN and changes in
cartilage volume or thickness in the knee joint of OA patients.
19
unclear.
4
In OA the characteristic pathologic finding is the loss of Meniscal tears are highly prevalent in both asymptomatic and clinically
hyaline articular cartilage, which contains no pain fibres. Other osteoarthritic knees of older individuals.
20
However, osteoarthritic
structures that are involved in late OA, such as joint capsule, knees with a meniscal tear are not more painful than those without a
ligaments, the outer third of the meniscus and the synovium, do tear, and meniscal tears do not affect functional status. Therefore, a
contain pain fibres. Periosteum and bone marrow are densely progression of JSN might result from a meniscal tear and extrusion and
innervated and represent a potential source of pain in patients with not from cartilage loss.
21
Limited data exist on how much cartilage loss
knee OA. It has been found that an association exists between pain has to occur before early radiographic OA can be detected. In
and bone marrow oedema.
5
Orthopaedic surgeons often come across conclusion, many patients may have considerably painful knees with
out-patient middle-aged female and male patients with a diagnosis of no radiological signs of OA.
early OA of the knee joint who complain of chronic knee pain and
present disproportionally minor or no radiological signs of early OA. It
has been shown that other disorders might be more common than OA
Apostolos H Karantanas is Associate Professor of Radiology
in the University of Crete, Greece and Vice President of the
in this category of patients.
6
With the advent of newer treatment
European Society of Musculokeletal Radiology. He is Chief
options, there is an increasing demand for early diagnosis before joint
of the Musculoskeletal Section and Head of the MDCT
Department in the Heraklion University Hospital. Professor
degeneration occurs. However, no established definition of early OA
Karantanas has published 90 Medline manuscripts and is
exists, either clinical or radiological. the author 16 book chapters, one book on theory and
praxis of MRI and 180 international announcements in
conferences. He has given 130 invited lectures in Europe
Plain Radiographs and Early Osteoarthritis
and South Africa. He is actively involved in the GALEN Project of the European Society of
Plain radiographs have been used for decades for the diagnosis and
Radiology, the School of MRI of the European Society for Magnetic Resonance in Medicine
assessment of progression of OA. In large clinical and epidemiological
and Biology, the Educational Committee of the European Association of Radiology and the
Sports Injuries Committee of the European Society of Musculoskeletal Radiology.
studies, the traditional radiographic method of assessing OA
progression is by estimating cartilage loss as measured by joint space
E:
apolsen@yahoo.com
narrowing (JSN). Osteophyte formation, sclerosis and subchondral
© TOUCH BRIEFINGS 2007 37
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