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Femoral Acetabular Impingement (FAI)

Femoral Acetabular Impingement (FAI)The hip joint has become one of my favourite joints in the entire body. This seemingly simple ball-and-socket joint created for mobility, load-bearing, and stability plays a critical role in linking the trunk with the rest of the leg.  Thus, any issue with the hip joint can affect structures below, the knee, ankle, and foot, and/or structures above, the pelvis and low back.  For some people pain in these adjacent areas can occur prior to any pain, discomfort, or limitations in the actual hip are noticed.

What is Femoral Acetabular Impingement (FAI)?

Most people associate issues in the hip with arthritis and hip replacements; however, there is another common issue in the hip that can affect people of any age and activity level.  Femoral Acetabular Impingement or FAI for short.  To understand what an FAI is you need a basic understanding of the anatomy of the hip.  As mentioned, the hip is a ball-and-socket joint.  The “ball” is the head (top) of the femur (thigh bone) and contributes the “F” to FAI.  It would akin to a tennis ball stuck on the end of the blade of an upside-down hockey stick.  The “socket” is comparable to an ice-cream scooper in shape and is located in each pelvic bone.  The proper name for the socket is acetabulum and thus contributes the “A” to FAI. The “I” of FAI is a bit more self-explanatory.  Impingement refers to pinching together, and in this case, the of head of the femur and the acetabulum are pinching together.

hip dislocationNormally, the shape of the ball-and-socket allow for free movement of the hip joint (see below); however, with an FAI the actual anatomy of the hip joint changes.  The cause of these anatomical changes can vary.  Changes can be congenital, meaning they are present at birth. More often, these changes are occur as a result of repetitive stress, strain, and non-optimal loading through the hip joint during participation in sports; therefore, these changes occur over time.  Changes can also occur based on the anatomy of your pelvis as that may pre-dispose you to increased load or altered force transmission through the hip joint with everyday activities like walking.   Regardless of the cause there are 3 types of bony changes that occur:

  1. CAM-TYPE – flattening of the junction between the tennis ball and blade of the hockey stick, which decreases the space for movement resulting in the bones pinching together at the end of the available range of motion
  2. PINCER-TYPE – extra bone growth at the tip of the socket (acetabulum) or a naturally deeper socket, which decreases the space for movement resulting in the bones pinching together at the end of the available range of motion
  3. COMBINATION OF CAM AND PINCER – both of the above occur at the same time


The femur and acetabulum have to come together for pinching to occur and this typically only happens during mid to end range movements.  When the bones pinch together it can result in pain in the groin, hip, or buttock areas, stiffness, and/or clicking, clunking, or giving way. Some people may go through life with no symptoms or awareness that these changes exist, while others may experience one or all of the above symptoms on a daily basis or with certain movements or activities.  As mentioned at the beginning, the hip links the low back and pelvis to the rest of the leg.  Therefore, for some their body may adapt to these changes and they may never feel pain in the hip region but instead experience low back pain or knee pain secondary to a compensatory strategy they have unconsciously adopted in order to avoid the pinching of the bones.


An X-ray can be used to diagnose an FAI; however, there are a cluster of tests your physiotherapist or chiropractor can complete to determine whether an FAI is likely. However, imaging results typically do not change the treatment approach as it is based on your specific symptoms, mobility, and strength.


It depends a bit on what your symptoms are, what activities you do or would like to get back to, the strength of your core muscles and the muscles surrounding your hip, and the mobility of your hip, pelvis, and low back. Based on your individual presentation some or all of the following may be used:

  • Mobilization of the hip, pelvis, and/or low back
  • Massage of the muscles surrounding the hip
  • Acupuncture of the muscles surrounding the hip
  • Core stabilization exercises
  • Strengthening of the gluts/buttock muscles
  • Adapting your movement patterns and improving recruitment of key muscles
  • Balance exercises
  • Sport-specific retraining


Typically, most people that are compliant with their treatment plan and especially their home exercises do well over a 6-12 week period depending on the severity of their symptoms.  Their range will likely stay the same, but they learn how to work in their new available range and strengthen new muscles to help stabilize the hip and reduce the frequency of pinching.   It is important to remember that once these changes have occurred they will not naturally reverse on their own. Surgery is an option; however, unless pain, mobility, and daily function are severely influenced the outcome usually does not have an impactful improvement and is typically not the best option.

It should be mentioned that those with an FAI are at an increased risk of a labral injury.  The description of this is a blog in itself!


I truly prefer to assess a person before prescribing exercises so that I can create an individualized and tailored program based on the patients specific needs.  However, the main areas that typically require strengthening in those with an FAI are the gluteal and core muscles and adding some balance training doesn’t hurt.  There have already been some great blogs written with exercises targeting these regions by other Rebalance clinicians and you can find the links below.

Gluteal Strengthening

Core Strengthening

Balance Training

Written By: Kaitlin Turner, Physiotherapist


  1. Klij PV, Heery J, Waarsing JH, Agricola R. The prevalence of Cam and Pincer morphology and its association with development of hip osteoarthritis (Clinical Commentary). JOSPT. 2018;48(4): 230-238.
  2. Pope D (Producer), Kemp J (Guest). (November 23, 2017). Physio Edge 074: Hip pain and femoroacetabular impingement FAI with Dr. Joanne Kemp [Audio Podcast]. Retrieved from:  https://itunes.apple.com/ca/podcast/physio-edge-podcast/id454714085?mt=2&i=1000395206271

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