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Diagnosis of knee pain

Diagnosing knee pain usually consists of a physical examination, as well as a careful look at your medical history.

Diagnosing your knee pain: the first steps to take

If you are worried about your knee pain, it is important to discuss your concerns with your GP or a specialist. They can then help diagnose the cause of your knee pain and recommend treatment based on your needs and requirements. 

We discuss the importance of an accurate diagnosis and how knee pain can be diagnosed. 

The various causes of knee pain can almost always be reliably diagnosed by an experienced musculoskeletal doctor or physiotherapist. To reach a diagnosis, a careful history of any previous pains or issues with joints is undertaken, as well as performing a physical examination.

Fortunately, there are effective treatment options and pain relief available for knee pain, including knee replacement and specialist exercises managed by a physical therapist.

Knee pain is a common complaint, and many of us will have experienced some form of it a number of times. Slips, trips, twists, knocks and other forms of knee injury all have the potential to damage the knee in various ways and cause pain.

There are many different reasons you may have knee pain, and self-diagnosis can be difficult. While some types of knee pain, such as those caused by a slight sprain or strain, can sometimes clear up naturally within a short time, when the pain is more severe or long-term, it is sensible to have your knee problems examined by an experienced doctor. 

A consultation is the by far the easiest way of finding out what exactly is causing your knee pain, and of making sure you get the best possible treatment without delay.

A physical examination of your knee is an important part of any assessment. As part of this, your doctor may bend or move your leg and knee into various positions to see how the joint is functioning and when and where you are getting pain.

To help with diagnosis, additional investigations such as X-rays or scans may be needed. These include:

  • X-ray: X-rays are a type of radiation. They can be used to produce images that show the bones of the knee clearly, and are useful when querying an injured area caused b fracture, dislocation or arthritic damage to the knee.
  • CT scan: Computerised tomography (CT) uses X-rays to produce cross-sectional images of the knee joint. These ‘slices’ can vary in width and are used to build up a very accurate three-dimensional image of the knee joint.
  • MRI scan: Magnetic resonance imagining (MRI) uses strong magnets and radio waves to produce very detailed images of the knee. Similar to CT, an MRI scan produces cross-sectional images of the knee.
  • Ultrasound: Uses high-frequency sound waves to create an image. Unlike other imaging options, ultrasound can be used to show movement of the joint in real time.
  • Arthroscopy: If your doctor thinks you may have damage to a cartilage or ligament, they may recommend an arthroscopy. This is a form of keyhole surgery, where a small cut is made in your knee and a thin tube (arthroscope) placed through it into the joint. The arthroscope has a bright light and camera at one end and allows the doctor to see clearly inside the knee joint.

Once the cause of your knee pain has been determined, your doctor will talk with you about treatment options and advise you on the best treatment options to get you out of pain and back to normal again.

Not all knee pain is equal. Even the phrase “knee pain” is a fairly generic way of describing a wide range of possible symptoms. For example, the pain you have may be:
  • Dull or sharp (aching knee pain);
  • Infrequent or constant (aching knee pain);
  • Generalised or localised (pain above knee cap), and
  • Short or long-term.

Mild, short-term knee pain is often a bit simpler to manage and treat than severe or long-term pain. However, any knee pain can significantly affect the quality of your life.

Knee osteoarthritis

Knee osteoarthritis is an extremely common cause of knee joint pain and is caused by erosion or damage to the cartilage shock absorber of the knee, with consequent severe knee pain.

Pain is usually on weight-bearing and gets gradually worse. This form of arthritis affects approximately eight million people in the UK. The knee is the joint most commonly affected by osteoarthritis.

Bursitis, or “housemaid’s knee”

This is caused by repetitive friction of the knee, from activities such as kneeling, resulting in a build-up of fluid over the knee, leading to pain and swelling at the front of the knee.

Usually responds well to self-management advice. Pain usually improves before the swelling, which can take longer to completely disappear.

If it becomes red or hot, more painful, or you feel unwell, clinician advice should be sought in case of potential infection.

Cruciate ligament injury (anterior and posterior)

The cruciate ligaments, anterior and posterior, prevent forward and backward movement of the femur on the tibia respectively. Similar to collateral ligaments, they are injured during sudden trauma, usually in high velocity injuries such as rugby, skiing etc. It is a significant injury that requires clinical assessment.

A joint swelling within 6 hours suggests bleeding in the joint and an urgent assessment via A&E is appropriate. Swelling arising over a longer period can be assessed more routinely. Difficulty with weight-bearing also demands more urgent assessment.

Knee cartilage pain

The knee joint has two different forms of cartilage. When clinicians refer to torn cartilage or cartilage pain, they are usually referring to a problem with the menisci. This is sometimes known as a meniscus tear. 

Pain from a tear to the medial meniscus, which lies on the inside aspect of the knee, is normally felt as a focused pain in this area and sometimes at the back of the knee. Lateral meniscal tears often result in focal pain to the outer aspect of the knee. Lateral meniscal tears are far less common than medial meniscal tears. Both forms of cartilage damage can be painful.

Anterior knee pain

Anterior knee pain is a generic term used to describe pain at the front of the knee. The term is descriptive and relates to a number of different diagnoses.

Collateral ligament injury

The collateral ligaments (medial – inside of the knee and lateral- outside) connect the bones across the knee joint.

These are usually injured during sudden twisting or changes of direction, often in contact sports such as football or rugby.

Patellar tendinopathy

This is generally a result of overuse, particularly from jumping-type or lunging activities, such as basketball or netball.

It causes pain, at the front of the knee, in the patellar tendon which runs from the knee cap (patellar) to the upper tibia.

Simple strain

Usually comes about after a minor injury, over activity or unusual activity, involving the knee. This should settle with self-management.

Kneecap (patellar) dislocation or instability 

Patella dislocation is usually obvious as the kneecap will become stuck to the side of the knee. Pain will be severe and require an assessment at accident and emergency. Instability is however, more common.

Your Consultant will be able to discuss medical advice, diagnosis or treatment with you in detail.