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PatelloFemoral Cartilage Defects – Is there always an Osteoarthritic Terminus?
243
New advanced imaging techniques are rapidly
improving in quality, in particular MR and
arthroscopy, revealing a spectrum of alterations
in the joint tissue that definitely identify more
pathology in the joint than thought, and loss of
joint homeostasis. The tissue changes in the
knee (in this case the PFJ) typically shows
changes in cartilage morphology (joint surface
fibrillation and single or multiple cartilage
defects), more diffuse cartilage loss, bone
marrow changes, slight subchondral sclerosis
and cysts, synovitis and some presence of joint
fluid… In these cases, MR and arthroscopy are
to a certain extent complementary thereby
providing an overall assessment of the knee
and its structural changes. It is with these tools
available in daily clinical practice, that it is
clear that in some patients early OA can be
diagnosed. Early OA would typically combine
slight clinical signs and symptoms as described
above but also displaying a number of structural
changes that are not seen on conventional
X-rays, and yet revealing by advanced imaging
changes identifying a knee that could progress
and develop established OA. With the current
knowledge of the development of these
technologies, it is surprising that the current
OA definition has not changed since 1986 to
capture early OA. Luyten
et al.
[14] suggested
that in view of an increasing number of clinical
investigations and trials with advanced imaging
techniques, it would be useful to define early
OA (with advanced imaging and arthroscopy
components of this classification). Having this
new classification system would be useful to
discriminate early OA from frank established
OA, and from patients with isolated (traumatic)
cartilage damage with an otherwise healthy
joint. It is suggested that there is a potentially
different (clinical) outcome for different
treatment approaches, so studied patient group
should be more specified in the future.
Classification criteria early knee OA
[14]
The ACR criteria for OA of the knee have been
published by Altman
et al.
[1], mostly the
combination of clinical and classical radio
graphic findings. It includes one of the
following three findings (age above 50 years,
joint stiffness with activity less than 30min,
crepitus of the involved joint), together with
radiographic changes i.e. osteophytes and joint
space narrowing on standardized X-rays. These
classification criteria have a 91% sensitivity
and 86% specificity.
The definition of classification criteria for
symptomatic early knee osteoarthritis is
certainly a challenge. However, these
classification criteria would be use in the future
based on the fact that the patient cannot be
classified as established OA by the current used
classification system. To make it clinically
relevant would still imply the combination of
symptoms/signs and structural changes.
However, strict radiographic criteria as defined
by Kellgren or Iwano will not suffice to capture
an early OA patient. Therefore, new
classification criteria allowing other methods
of structural assessment such as MR and/or
arthroscopy could be proposed.
As suggested above, and in view of the current
classification criteria for established OA,
Luyten
et al.
proposed the following [14]: A
patient can be classified as having early OA of
the knee based on the following clinical and
imaging criteria:
Clinical Criteria
Pain in the knee
(e.g. at least 40mm on VAS
scale, and/or duration e.g. for >10 days in the
last 3 months, or knee pain at least one day
during the last 4 weeks)
.
+ two of the three following criteria:
Imaging Criteria
1)
Iwano grade I-II (probable osteophytes and/
or joint space narrowing).
2)
Arthroscopic findings: ICRS grade 1-2.
3)
MR findings demonstrating articular carti
lage degeneration and/or subchondral bone
marrow lesions…