What is an ultrasound?
Ultrasound is high-frequency sound waves produced by a special machine. They can provide very useful images of the tissues within the body, and it is extremely useful in assessing various musculoskeletal conditions involving the tendons, muscles, joints and adjacent soft tissues. Unlike X-rays, ultrasound is harmless and involves no radiation or other harmful side effects.
Do I need a hip ultrasound scan?
Hip ultrasound is very useful in assessing certain hip joint conditions. These include:
Hip joint effusion. This refers to the presence of excess fluid within the hip joint. This can happen due to different causes, including (hip injury, hip osteoarthritis, inflammatory arthritis and infection). An ultrasound scan can assess the size of the effusion and if there is any active inflammation (which can be seen in a specific type of inflammatory arthritis “like rheumatoid arthritis”.
Hip trochanteric bursitis/Greater trochanteric pain syndrome. This inflammatory condition affects the tendons (and possibly the bursa) at the outside of the hip, causing pain and discomfort. The condition is usually caused by irritation of a special group of tendons (called the gluteal tendons) that attach to a bony prominence at the outside of the hip (called the greater trochanter). Therefore, this condition is sometimes referred to as “gluteal tendonitis”. Sometimes, it is associated with inflammation of the adjacent "trochanteric bursa". The trochanteric bursa is a thin fluid-containing sac found at the outside of the hip, next to the greater trochanter and hence the name of the condition. Ultrasound is useful for assessing the gluteal tendons for any inflammation or tear. It can also assess the bursa for any inflammation, a condition termed "trochanteric bursitis". Trochanteric pain syndrome is an umbrella term used to describe the different conditions that could affect this area. To find out more, please read our article about Hip trochanteric bursitis.
Assessing soft tissue lumps around the hip joint. Ultrasound is particularly useful when there is a suspicion of a groin hernia.
Ultrasound is useful in performing dynamic assessment, particularly for snapping hip syndrome.
Probably the most important use of ultrasound in the hip is to guide injections and treatment. Ultrasound allows for direct visualisation of the needle to ensure that the medicines are injected into the exact targeted site. There is significant evidence that ultrasound-guided injections provide better levels of pain relief and more prolonged effects compared with injections done without imaging guidance. Performing these injections under ultrasound guidance allows for visualising the adjacent structures and reduces the risk of tissue injury at the injection site.
The different conditions where ultrasound-guided treatment can be useful include:
There are different treatment options/injections that can be done under ultrasound guidance to help manage hip pain. These include:
What are the limitations of a hip ultrasound scan?
The deep structures of the hip cannot be adequately assessed with ultrasound. These include the labrum and articular cartilage of the joint. While ultrasound is excellent in assessing soft tissue lumps, assessment with a hip X-ray or MRI would be more useful if there is a possible bone lesion.
Hip ultrasound vs hip x-ray and MRI
A hip X-ray (or hip radiograph) is a black-and-white image produced by sending an X-ray beam through the area of the hip and getting the images on a film. It is usually the first type of imaging done when there is a hip problem, particularly if there is suspicion of hip arthritis or fracture around the hip. The bones absorb the X-ray beam more than the other surrounding soft tissues, and therefore bones are usually very well seen on X-rays, unlike ultrasound. However, they cannot assess the soft tissues like ultrasound and involve a small dose of radiation. To find out more, please see our article about hip X-rays.
An MRI examination uses strong magnetic fields and radio waves to produce detailed images of the hip. MRI is useful to assess internal structures like the hip joint labrum and the articular surfaces. MRI, however, is more expensive and requires you to stay still for 20-30 minutes inside a special machine. To find out more, please see our article about hip MRI.