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The Knee Joint
An MRI scan is
the best way to find the cause of knee pain, stiffness or
locking. Mobile diagnostics MRI scans are performed on a an
open mobile MR scanner operating in Cambridge, Carlisle, Essex,
Brentwood, St Albans, Highgate and London. Scans are low cost...£250
for an uninsured patient. Private and NHS patients can be
examined.
Osteoarthritis
("Wear and
tear" or "degeneration"). This is one of the commonest joint
conditions and while typically a disease of the elderly, can
occur in young and middle-aged patients for a variety of reasons.
These include previous joint trauma, genetic factors, high body
mass index (overweight patients)or damage to the joint cartilages.
The value of MR is to answer the following questions:
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Are
osteoarthritic changes present? |
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If
so, how advanced is the degeneration |
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Are
there any treatable lesions, such as a torn meniscus (cartilage)
or loose body, which can be corrected
and slow the progression of the osteoarthritis |
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Is
the degeneration at a stage where joint replacement should
be considered? |
The main feature of joint degeneration is the wearing away and
thinning of the articular cartilage, which is the slippery substance
which lines the joint surfaces and normally allows free and
painless movement of the joint. Once
the cartilage has worn away the bone will become damaged and
the joint becomes more painful and may be restricted in movement.
MRI will demonstrate the amount of articular cartilage loss,
the presence or absence of associated bone damage and the state
of the menisci. This
information will allow planning of optimum therapy.
MRI will give far more information than the plain radiograph,
which only shows the bone and is generally most useful in end
stage disease. The plain films give no information
about articular cartilage, and damage to the menisci and ligaments
of the knee. However the MR scan will show any damage to the
internal structures of the knee, and also provide information
about the tendons, muscles and other soft tissues , and will
identify any inflammation within or adjacent to the knee joint.
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An
MRI scan of a normal knee. The cartilage (meniscus) is shown
as a small black bowtie like structure sandwiched between the
bones on either side of the joint, which appear white. Note
the articular cartilage, which appears grey on this image, lying
between the meniscus and the bone. |
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| This
is the knee of a an 46 year old man who had had increasing pain
in the right knee following an awkward fall 4 years previously.
A damaged meniscus is shown (red circle) with a blue arrow indicating
a region of articular cartilage loss. The loss of the
meniscus, which should act as a shock absorber, has caused the
articular cartilage (joint lining) to wear away. |
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Loose Bodies
A
fragment of cartilage, or small chip of bone from an old injury may
become loose within the joint and cause pain and intermittent stiffness
or locking. There is usually an effusion (fluid) within the joint
when a loose body is present and the loose bodies are usually well
shown on the MRI scan. Once identified and located, the orthopaedic
surgeon can remove the offending material during a telescope examination
of the joint (arthroscopy).
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This
young man had complained of variable swelling and pain in the
knee over the last 18 months.The MRI scan showed a small loose
body (circled) within the joint. This was easily removed at
arthroscopy and the patient's symptoms resolved. Luckily, no
damage to the articular cartilage had been sustained and the
cartilage, which appeared normal on the scan, was confirmed
to be normal by the surgeon |
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Unsuspected
Fracture
Small fractures will not always be shown up on standard knee x-rays.
| This
amateur footballer had complained of pain in the knee since
a bad fall following a hard tackle.. He had been unable to continue
playing. X-rays obtained on the day of the injury had not shown
any abnormality.The MRI scan shows a fracture of the tibia (arrowed),
which included the attachment of the posterior cruciate ligament.
This is an important ligament which stabilises the knee. Tears
and detachments of this ligament are relatively rare.This patient
was able to return to his football two months after surgical
fixation. |
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This 14-year-old boy, who was a keen athlete, complained of persistent
pain in the right knee joint, which was mainly at the front of the
knee. Clinical examination did not demonstrate any weakness of the
ligaments and was a full range of movement. MR showed abnormality
at the patellar tendon insertion to the tibial tubercle, and fluid
immediately posterior to the distal tendon. This is the typical appearance
of Osgood Schlatter's disease. This condition is more descriptively
known as a traction apophysitis of the patellar tendon and is due
to recurrent minor stresses where the patellar tendon attaches to
the tibia. It is common in adolescents, particularly when there is
a high level of physical activity. This diagnosis cannot be made reliably
with x-rays (which do not show fluid, or inflammation in the bone
and tendon).
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