FAI: The ‘New’ Impingement?

Arthritis is a well-known condition and its prevalence is increasing each year. However, a newly discovered dysfunction of the hip is being discussed in the medical field and in various journals. This is Femoral Acetabular Impingement (FAI).

The purpose of this article is to look closer at what FAI is, treatment options, and most importantly, training strategies to prevent FAI with your clients.

The Shoulder Complex

The shoulder is a ball and socket joint comprised of four joints — the glenohumeral joint, the acromioclavicular joint, the sterno clavicular joint and the scapulothoracic joint. This construction allows someone to move his or her shoulder in six different motions. Because of this, the shoulder is vulnerable to injury. Each joint is surrounded by connective tissue(fascia), ligaments and muscles that support the shoulder both statically and dynamically.

The Hip Complex

The hip complex, like the shoulder, is also a ball and socket joint. It is designed slightly differently, however, and is supported via ischiofemoral, iliofemoral and pubofemoral ligaments. It has six different motions and is supported via anterior, lateral and posterior hip musculature that allows the lower body to perform daily activities such as walk, climb stairs or perform dynamic athletic movement in three different planes that involve forward, lateral, diagonal and movements that are combined such as stopping and turning as seen in most sports. As seen in Figures 1& 2, the iliopsoas muscle is a postural muscle (tight) whereas the glute medius is a phasic (muscle) weaker according to the research.

Figure 1. Anterior hip complex Figure 2. Posterior hip complex


Pathomechanics of the Hip

In the sagittal plane, during hip flexion (~120 degrees), the femoral head translates down (inferior) as the glute maximus creates a downward pull and the iliofemoral ligament is on slack. During hip extension (~20 degrees) iliopsoas is eccentric lengthened with the iliofemoral ligament. In the frontal plane, during hip abduction (~40 degrees) the femur outwardly translates and the movement is restrained by the adductors(adductor magnus and brevis primarily) as the pubiofemoral ligament is tensioned. During hip adduction (~25 degrees), the femur glides down and out as the tensor fascia latae, ischiofemoral ligament and glute medius is eccentrically lengthened.

Pathophysiology of FAI

The mechanism underlying femoral-acetabular impingement is that normal motion of the hip, most often flexion, results in abnormal contact between the femoral head or the proximal femur at the head-neck junction and anterior rim of the acetabulum. Increased or repeated wide movements, such as those associated with martial-arts kicks, promote FAI results in microtrauma. This can be a result of morphologic abnormalities in the proximal femur, the acetabulum, or more frequently a combination of the two.

Figure 3. Pincer and Cam Impingement

There are two main variants: pincer impingement, in which the acetabular rim impinges on the femoral neck at the limit of the range of motion; and cam impingement, in which the position of the femoral head is too large to pass in the acetabulum, and when the hip is flexed, this stresses the rim of the labrum.2 This is seen in Figure 3. There is substantial evidence supporting the hypothesis that FAI is a major etiologic factor in the pathophysiology of secondary osteoarthritis of the hip.3

Clinical Presentation

FAI, according to the research, typically affects the young- or middle-aged patient and typically presents with deep groin pain, frequently exacerbated by athletic activities that demand deep hip flexion, or by prolonged walking, sitting or driving. These symptoms overlap with those of labral tears where patients usually present with an insidious onset of deep groin pain, which is aggravated by walking, pivoting on the affected side, impact activities or prolonged sitting. Mechanical symptoms from the hip such as painful locking or giving way are common presenting features if a labral tear is present. It is now recognized that many patients previously diagnosed to have an isolated labral tear may actually have had unrecognized FAI. 4

Next month, we will focus on treatment options an training options for those with FAI.


1. Lawrence RC, Delson DT, Helmck CG et al. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Arthritis Rheumatology. 58(1) pgs: 26-35. 2008.

2. Laude, F. et al. Anterior femoroacetabular impingement. Joint Bone Spine. pgs: 127-132. 2007.

3. Clohisy, J et al. Surgical Treatment of Femoroacetabular Impingement: A Systematic Review of the Literature. Clinical Orthopedic Related Research.. Pp: 555-564. 2010

4. Hossain. M. et al. Current management of femoro-acetabular impingement. Current Orthopaedics. 22. Pgs: 300-310. 2008.

About the Author

Chris Gellert, PT, MPT, CSCS, CPT is the President of Pinnacle Training & Consulting Systems, LLC, a consulting and education company that is committed to create and provide evidenced based educational material in the form of home study courses, dynamic live seminars, mini-books, DVD’s and other electronic media that educates personal trainers taking their knowledge and training to another level. Chris has extensive clinical experience having worked with primarily orthopedic patients, spinal injuries, post-surgical conditions, traumatic and sport specific injuries. As both an experienced physical therapist and certified personal trainer, a national fitness presenter at the following conferences;(Club Industry, ECA, IDEA, IHRSA, NSCA, TSI Summit), he continues to write for various publications and websites, consults and is presently pursuing Postgraduate studies in Physical Therapy & Clinical Reasoning in Australia.




These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.
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