The Knee Joint

MRI is the investigation of choice for patients with unexplained pain, swelling or abnormal function, such as restricted movement or intermittent locking. An MR scan can demonstrate conditions such as the following:

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:

	Are osteoarthritic changes present?
	If so, how advanced is the degeneration
	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
	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.

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.

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.

MR scan of a knee showing trauma from a fall

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).

Magnetic Resonance Imaging showing small loose body in the kneww joint

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

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.

$Magnetic Resonance scan showing a fracture now diagnosed by xray$

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).

MR scan showing apophysitis of the patellar tendon

Sports Injuries

Foot and Ankle MRI scans can investigate degeneration or trauma from sports injuries or running and diagnose Mortons neuroma, Achilles tendonitis and Sever’s disease.

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Personal Injury Cases

We have done over 2000 medicolegal reports including attendance at Civil and Crown courts to present evidence.

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Chronic Joint Pain

An Open MR scan will investigate unexplained pain, swelling or restricted movement

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