The Role of Medical Imaging in Physiotherapy Care

By: Samuel Yiu

A common question that I often get asked by clients is if they should go for medical imaging to confirm their injury. Oftentimes, the answer to this question depends on a few clinical variables. The two most important questions I consider are;

1. Will the image results significantly change the physiotherapy treatment plan or outcome?
2. Does this condition require more than Physiotherapy treatment, and if so, will imaging be needed to initiate the process?

Medical imaging such as X- Rays, Ultrasounds, and MRIs are helpful tools for diagnosing injuries and determining how long an injury might take to heal.  It can also inform which treatment options may be best for the patient (ie. surgery vs. conservative rehabilitation). The purpose of this blog post is to provide a brief summary of the different types of imaging that are commonly used to evaluate musculoskeletal/sport injuries and to discuss which situations may warrant consideration for medical imaging from a physiotherapy perspective.

X-rays

X-rays use electromagnetic waves and radiation to create images inside of your body. The images are formed through various shades of black and white. The density of a tissue affects how much radiation is absorbed, which in turn determines how dark/bright the structure will turn out on the image. The denser a structure is (ie. bones), the whiter the structure will be. Other structures such as muscles, ligaments, and nerves are not seen on X-rays as the density of these tissues are not sufficient to emit enough lighting from the radiation.

X-rays are best at telling us about the health of our bones and are often the first source of imaging used to determine if there are fractures and dislocations.  X-rays can also evaluate how bones interact and align with each other at their joints and can show underlying conditions such as arthritis.

Ultrasound

Ultrasound imaging uses sound waves to produce an image inside of your body.  The technician will place a transducer on the skin, which sends high-frequency sound waves in and out of the body.  The sound waves are then converted into an image by a computer.  Ultrasound does not use any radiation and can show motion of the structures in real-time.

When it comes to musculoskeletal injuries, ultrasounds work well for investigating structures such as tendons, muscles, and ligaments, that all lay outside of the joint. .  Common injuries that ultrasound imaging can pick up include muscle tears, inflammation around tendons, and ligament sprains.

MRI

MRI, also known as Magnetic Resonance Imaging, uses a magnetic field along with radio waves to produce a comprehensive image.  It is often considered the most robust form of medical imaging, as it produces a total view of joints (inside and outside), muscles, ligaments, cartilage, and bones.  MRIs are commonly used for injuries/conditions that are located deep into a joint or impact a large area of the body, such as ACL tears, meniscus injuries, spinal disc herniations, and hip labral tears.

MRIs are often in high demand and with limited machines and technicians across the country, there are often long wait times to receive an image.  As of September 2021, the average wait time for an MRI in Ontario is 68 days, although these wait times can vary based on which city you reside in and the urgency for imaging to be completed. *

Ultrasound vs. MRI

Ultrasounds present with limitations and there are scenarios where MRIs are required to investigate structures that ultrasounds cannot pick up. Generally, an MRI is required for investigating deeper structures inside a joint such as cartilage, bones, or deeper ligaments.  Ultrasounds work well for smaller surface areas and structures that are closer to the surface of the body such as muscles and tendons.  If a patient needs a more detailed view of an entire joint, MRIs are the better choice.  However, more often than not, physicians may send you for an ultrasound first as wait times are usually shorter.

Closing Thought

While the use of medical imaging may be helpful in informing a diagnosis, it should rarely be used alone to explain the cause of your pain.  Medical imaging only shows the structural integrity of body tissues.  Pain is complex and it is not always the case that structural damage equates to dysfunction or vice versa. For example, an individual could present with degenerative discs in their low back and not experience any low back pain, or another individual could present with chronic knee/shoulder pain without any structural damage to the joint, ligament, or muscles.  In addition, the findings from medical imaging are not always completely accurate, as the results are dependent on a radiologist’s or surgeon’s interpretation. In some cases, the range of agreement when interpreting imaging results can be shockingly inconsistent.

In Ontario, physiotherapists are unable to refer their clients directly for imaging. This means that an individual must see a physician first to get their requisition for the imaging procedure. However, physiotherapists can still play a critical role in helping determine whether or not you need imaging. If your physiotherapist suspects that you need medical imaging, they may educate you on what to say to your doctor and recommend a specific imaging procedure for you to ask for. Your physiotherapist may also choose to provide your doctor with a letter to further explain why their clinical findings warrant further investigation through imaging.