FAI (femoroacetabular impingement)

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Femoroacetabular impingement

Femoroacetabular impingement (FAI) is a multifactorial hip disease in which pain is a direct result of a collision of femoral head (the ball of the hip joint) with the edge of the acetabula (the socket of the hip joint). The hallmark of the disease is pain provoked by hip flexion. Although impingement occurs during flexion of the hip joint such as with sitting, squatting and lifting the hip. Once the impingement is established the pain may appear on walking, kicking and sporting activities involving body rotation over the planted leg. This occurs because the hip joint labrum becomes damaged and the capsule becomes inflamed. The joint space may not become decreased until the progression of the disease. Labral tears may or may not be present with FAI.


Most common location of pain is in the groin,

Pain presentation

however it may appear on the side or the back of the hip.


FAI is a disease of young athletic adults. However, hip impingement also occurs in middle age population as well and account for 10-15 % of adults with any hip diseases. In older adults the changes in the hip joint occur earlier but may manifest later in life.


There are 2 types of FAI; Cam and Pincer deformity. However majority of cases are of a mixed type.

CAM type – is a widening of the femoral neck. Pincer type is when there is an outgrowth of the edge of the bony acetabula.

Types of hip impingement: normal
Types of hip impingement: cam
Types of hip impingement: princer
Types of hip impingement: mixed


Anatomy of the hip

Hip joint is anatomically the most complex joint in the human body. It is a part of functional unit called lumbopelvic-hip complex and as such plays a decisive role in mobility of this complex .The intrinsic stability of this joint is provided by the labrum and the capsule-ligamentous complex. The labrum is a fibrocartilagenous pad which smoothes the surface of the acetabula providing adherence and congruency to the movement of the femoral head (the ball) in the acetabula (the socket).

The articular surface of the joint is layered with hyaline cartilage- which functions to decrease friction and helps to increase range of motion. The anatomy of the hip is designed in such a way to create negative pressure between the surface of the femur and the acetabula. With Femoroacetabular impingement this pressure is lost.


Research shows that children with abnormal structural development of hip bones are predisposed to developing FAI, however there are many patients with FAI who don’t have any predisposing factors. The collision of the head of femur with an acetabula as an abnormal contact results in decreased range of motion, inflammation, and eventually may lead to wear and tear of the joint cartilage.. Functionally, FAI will lead to hip and pelvic instability, pelvic misalignment, muscle misbalance ,compensatory weight distribution and loss of balance.




Heavy laborers

Heavy laborers

Trauma to the hip

Trauma to the hip

Inflammatory arthritis

Inflammatory arthritis

Congenital hip dysplasia

Congenital hip dysplasia

Congenital hip dislocation

Congenital hip dislocation

Legg-Calves-Perthes disease

Legg-Calves-Perthes disease

Significant anterior pelvic tilt

Significant anterior pelvic tilt

Structural anatomical abnormalities of the hip joint

Structural anatomical abnormalities of the hip joint



Patient history and clinical examination are sufficient for diagnosing FAI. Diagnostic ultrasound may show impingements, labrum tears and associated soft tissue damage. However, MRI is much more accurate for determining the stage and extent of FAI. If surgery is not being considered, a combination of Xray and ultrasound is enough to guide rehab and/or injection therapy.


Please explore more advanced diagnostic option unavailable anywhere else:


Hip dysfunction and pain can be a complex issue due to interactions of the trunk, pelvis, low back, groin and hip joint. Physical therapy and rehabilitation that is based only on subjective clinical analysis often addresses the symptoms without resolving the underlying cause.


At NYDNRehab, our groundbreaking motion analysis technology and high resolution diagnostic ultrasonography have enabled us to develop a battery of tests that perfectly reveal the dynamic functional pathology of the hip joint and pelvis. Our tests are evidence-based protocols that are considered to be the gold standard in the world of research.

Our testing protocol includes:


Combined lumbopelvic hip stability test using DLEST methodology with C.A.R.E.N., our computer assisted rehab environment


Hip joint stability test using DLEST methodology with C.A.R.E.N.


3D star excursion banner test (SEBT) for assessing the involvement of the hip joint and muscles in postural stability


3D gait or running analysis


3D kinematic joint angle analysis during a squat, lunge, drop jump and pelvis on hip rotation


Rehabilitative ultrasonography for viewing intrinsic hip stabilizing muscle activation patterns

We also perform neuromotor testing with DD Robotech for:

  • Proprioception
  • Tracking ability
  • Force sense
  • Critical power
  • Reactive power
  • Flexibility


Surface electromyography (SEMG) may be added to any of the above tests when needed.

Based on our experience and evidence-based information, we believe that physical therapy and rehabilitation should be based on objective quantifiable data.


Although arthroscopic techniques have been dramatically improved and there is much more research data in the last five years the first treatment of choice is certainly conservative. Research shows that 85% of patients with Femoroacetabular hip impingement will improve with physical therapy.Research also shows that those patients with FAI who prehabed have better outcomes after the surgery.


At NYDNRehab we have extensive experience treating FAI. Based on functional evaluation and gait analysis we create an individualized treatment plan. Treatment options may vary depending on type and stage of the FAI. FAI treatment is always a combination of manual therapy, hip specific physical therapy exercises. We use our unique C.A.R.E.N (Computer Assisted Rehabilitation Environment) technology to retrain symmetrical weight bearing and equalize weight shifting which is always disturbed in patients with Femoroacetabular impingement. However, in our experience of trying different physical therapy methods for hip impingement pain we found DNS (dynamic Neuromuscular Stabilization) approach to be the most effective.

Treatment in clinic NYDNrehab


Femoroacetabular impingement (FAI)

Femora Acetabular Impingement ( FAI) is a relatively new hip joint diagnosis, which produces pain mostly in active individuals or people with predisposing occupations. The condition itself is not new at all, however current understanding of its pathology came with recent advancement in skeletal imaging.In this condition bony conflict between anatomical prominences of pelvis and femur occur during hip movement. This contact occurs during hip flexion and is pathological due to its destructive effect to the hip labrum and eventually to the hip cartilage.
This condition is a precursor of hip arthritis( arthrosis).

Patients experience symptoms of hip movement stiffness to sharp pain in the groin after sporting activities.

The sports, which usually lead to FAI, are: soccer, hockey, martial arts, ballet and yoga.

This is a list of anatomical predisposing factors:

  • Congenital hip dysplasia
  • Prominent femoral head-neck junction
  • Elliptical femoral head
  • Femoroacetabular anteversion
  • Femoroacetabular retroversion
  • Coxa valga
  • Coxa Varum
  • Coxa profunda
  • Protrusio acetabulum

Other predisposing factors are more functional or traumatic. These range from direct trauma to distant trauma resulting in alteration of biomechanical relationship in the kinetic chain.

The progression of this disease is interesting occurrence. One may ask himself that if all anatomical predisposing factors are congenital why does one develop symptoms in the 3d or 4th decade of life, (professional athletes develop symptoms in the second decade)?
The answer is simple. In FAI congenital bone anomalies are varied in combination of it’s severity and overplay with joint and movement dysfunction in other regions of the body. Majority of people with these congenital anatomical defects in the hip area may never experience pain or only develop hip arthritis(arthrosis) in 7 the decade of life. This is because these people simply don’t participate in sports or choose sports, which are not damaging to the hip with congenital imperfections.

Many people with FAI suffer from back pain and herniated disc disease for years prior to developing symptoms of hip pain. Majority of these patients are operated for disc hernia without successful outcomes or only with temporary pain relieve.

FAI Diagnosis

The golden standard of radiological diagnosis for FAI is special CT scan series. This is, however only necessary in case surgical intervention is entertained as there is enormous dose of radiation involved in this special procedure.
Otherwise, a combination of X- ray with MRI or diagnostic ultrasound and clinical examination can be specific enough for treatment.

Femoracetabular Impingement (FAI) Pain Treatment

FAI pain treatment depends on precise structural and functional diagnosis as well as consideration of compensatory factors, which usually play a significant role in the rehab process. The challenge of conservative treatment of FAI lies in its complexity of presentation, as no FAI patient is similar to another FAI patient as far as rehab is concerned. Also, since hip joint is a major weight bearing joint in the human body it’s gait deviations are engraved in the motor control and the biomechanics of the whole human body.

Femoraceabular (FAI) pain treatment also depends on careful elimination of provoking movement and postures.
Video gait analysis is the best technological modality to tease out and precisely describe all movement aberrations in pelvis and the rest of lower extremity. These aberrations are not visible to human eye and therefore biomechanical relationship of all the components of lower kinetic chain cannot be properly addressed without it.

Please explore our gait analysis page.

Even with all the complexity of the FAI pain syndrome, conservative care is successful in experienced hands within 6-8 weeks in initial presentation and up to 6 month of rehab in chronic cases.

Surgical Intervention

Surgical intervention should only be reserved to professional athletes or very few patients with greater damage of hip intrarticular tissues.
The surgical intervention does not correct the cause of impaired movement but only remove the bone conflicting anatomy.
Since data for arthroscopic FAI repairs is relatively new , we can not estimate yet how successful these surgeries are. Especially giving very , very long recovery from this surgery this type of procedure should only be reserved as a last reserve.

Please check out our pages for the running gait lab, the alter-g treadmill, Biofeedback motor control training with real time force plate analysis, and shockwave therapy to see how these technologies can help you.


In this instance, an athlete was originally diagnosed with minor quadriceps muscle strain and was treated for four weeks, with unsatisfactory results. When he came to our clinic, the muscle was not healing, and the patients’ muscle tissue had already begun to atrophy.

Upon examination using MSUS, we discovered that he had a full muscle thickness tear that had been overlooked by his previous provider. To mitigate damage and promote healing, surgery should have been performed immediately after the injury occurred. Because of misdiagnosis and inappropriate treatment, the patient now has permanent damage that cannot be corrected.

The most important advantage of Ultrasound over MRI imaging is its ability to zero in on the symptomatic region and obtain imaging, with active participation and feedback from the patient. Using dynamic MSUS, we can see what happens when patients contract their muscles, something that cannot be done with MRI. From a diagnostic perspective, this interaction is invaluable.

Dynamic ultrasonography examination demonstrating
the full thickness tear and already occurring muscle atrophy
due to misdiagnosis and not referring the patient
to proper diagnostic workup

Demonstration of how very small muscle defect is made and revealed
to be a complete tear with muscle contraction
under diagnostic sonography (not possible with MRI)


Complete tear of rectus femoris
with large hematoma (blood)


Separation of muscle ends due to tear elicited
on dynamic sonography examination

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