Femoroacetabular impingement (FAI) is characterized by pathologic contact during hip range of motion (1). The idea of hip impingement, although noted in the 1930s, is becoming an increasingly prevalent concern with today’s athletes and the general population (2,3). The purpose of this review is to describe FAI pathology, explore current treatment approaches, and outline example exercise interventions that may improve quality of life for individuals diagnosed with FAI.
The hip joint is a synovial articulation of the pelvis with the femur, connecting the axial skeleton with the lower extremity (Figure 1). The femoral head is a ball-like structure resting inside the acetabular socket of the pelvic girdle. This ball and socket feature allows the hip to operate in a multiplanar fashion, a foundational necessity to facilitate human ambulation and functional movement patterns such as lunges and squats. The normal femoroacetabular joint functions as a concentric ball and socket joint in hip range of motion between 30 degrees of flexion and 15 degrees of extension. Outside of that range, femoral head translation occurs (4).
In athletes or clients with an FAI diagnosis, the joint motion between the skeletal architectural prominences of the femoral head and the acetabular rim is faulty. The impingement involves a change in the surface of the hip joint that predisposes it to damage, resulting in stiffness and pain. The two main classifications of FAI are cam impingement and pincer impingement.
Cam impingement (Figure 2) has abnormal morphological features at the aspherical portion of the femoral head. This can be referred to as the femoral cause of FAI (1,5). There can be abnormal bone growth on the neck or head of the femur, which sometimes lends itself to the nickname of the “pistol grip” deformity. The pinch occurs when the femoral head rotates inside the acetabulum into flexion, adduction, and internal rotation (FADIR). Such rotation of the femur inside the joint capsule can be incredibly painful and reduce the ability to properly load in movement patterns. Cam impingement is more common in males than females (6). Males also have greater height of deformity, even when normalized for the size of the femoral head (6). Cam deformities have an incidence of 14% to 24% in the general population and are more common in athletes (7).
Cam deformities are most often measured with alpha angles and femoral head-neck offsets via radiographic imaging (6). Both increased alpha angles and femoral head-neck offsets are associated with cam deformity (6,7). Athletes have a four-degree higher alpha angle than nonathletes. Athletes who participated at a national or international level had a seven-degree higher alpha angle than nonathletes (7).
Cam deformities seem to develop before closure of the epiphysis of the femoral head (6,7). They consistently have increased extension of the capital femoral epiphysis down the superior femoral neck with the cam location close to the location of the physis (6). The fastest increase in alpha angles can occur between ages 12 and 14 years old (7). If soft tissue hypertrophy at the femoral head-neck junction precedes extension of the ossified epiphysis, then this may suggest a reason for loss of internal rotation before radiographic evidence of cam deformity (6). Alpha angles have been found to increase from nonpathologic to pathologic range at the time of growth plate closure (6).
In pincer impingement (Figure 3), there is an excessive prominence of the anterolateral rim, or an over-coverage and abnormal bone growth of the outer rim of the acetabulum (3). The primary movement that elicits pain is flexion as the femoral head rolls and abuts the over-coverage of the socket. This can lead to consistent microtraumas that compress the labrum and articulating joint structures (3). The pincer impingement is common in middle-aged active women (8). Nearly 86% of persons diagnosed with FAI present both cam and pincer pathologies (1).
The causes of FAI are not well understood. Faulty mechanics during activities of daily living or during exercise could be contributing factors to the compressive forces between the femur and acetabulum. Engaging in vigorous sporting activities has been associated with cam deformation (6). Repetitive high-intensity loading during sport played throughout a critical period of hip development may be the most salient factor for cam development, causing epiphyseal hypertrophy with extension along the anterosuperior femoral neck (7). This may be due to juxtaphyseal trauma or physeal shear stress, which leads to reshaping of the physis (6). The potential degenerative nature of FAI impacts the integrity of the labrum, the rim of soft fibrocartilage that surrounds the acetabulum. Such a disruption to the labrum may reduce the natural ability of the body to protect the joint surfaces of the hip. FAI may be a contributing factor to early onset of osteoarthritis (9). Adolescent athletes with cam deformity and limited range of motion are at increased risk of early degenerative arthritis (4,10).
FAI SIGNS AND SYMPTOMS
In a recent consensus statement, Griffin et al. describe FAI as a motion-related clinical disorder of the hip presenting patient-reported symptoms, clinical signs, and image findings indicating premature contact between the proximal femur and the acetabulum (2). The symptoms are pain presenting in the hip, groin, back, and buttocks with motion (2). Other common symptoms include the following:
- A deep ache (3,7,10,11),
- Difficulty sitting (2,12),
- Sharp pain when standing up from a squat (3,13,14),
- Pain with movements like cutting, jumping, pivoting, or lateral movements (3,14,15),
- Feelings of inflexibility at the hips (3,13).
Patients may describe the experience of the abutment of the articulations as clicking, catching, locking, restricting, and stiffening (2). Pain relief may be briefly achieved in execution of the “C” palpation strategy (Figure 4). To execute this palpation strategy, an individual with FAI can place their cupped hand above the greater trochanter with their thumb, place their fingers anteriorly into the groin and hold; this pressure can often attenuate symptoms temporarily (3).
DIAGNOSIS, SURGERY, AND SURGICAL OUTCOMES
Diagnosis usually occurs with assessment of patient-reported symptoms, a physical exam, and diagnostic imaging. A physical examination maneuver may involve gently rolling the thigh internally and externally as the patient lies supine, otherwise known as the log roll test as shown hereinafter (3,16) (Figure 5A, B).
Patient hip internal rotation and flexion range of motion are assessed to determine clinical criteria. Often, magnetic resonance imaging is required to get a clearer picture of the bony impingement. Although nonsurgical interventions such as therapy and physical activity modification can be pursued, surgery for FAI is on the rise. Recent reports indicate a 25-fold increase from 2006 to 2013 (17). The Warwick Agreement on FAI (2) presented three main areas for surgical intervention: symptoms, clinical signs (range of motion), and diagnostic imaging.
However, in a review article to determine standardized criteria for open and arthroscopic surgical treatment for FAI, criteria for surgery may be incongruent with recommendations from the Warwick Agreement (9). For example, 56% of the included studies (n = 60 of 108) reported at least one component in all three categories from the Warwick agreement. Yet, 92% of 108 studies reviewed reported that hip diagnostic imaging was the most important criteria for determining FAI surgery (9). Diagnostic imaging is a critical criterion for surgery but may have limitations. Holistic assessment should use clinical evaluation such as restrictions in range of motion and consider failed nonsurgical approaches such as nonsteroidal anti-inflammatory drugs (NSAIDs), activity modification, and physical therapy along with diagnostic criteria for surgical intervention. In the emerging focus on hip pathology and the rising number of surgeries, consistent criteria to determine surgery intervention can ensure proper patient selection for surgery (9).
Outcomes from hip surgery to treat FAI have been mixed, but arthroscopy may have fewer complications with better outcomes. In a recent systematic review of eight studies with more than 400 patients undergoing surgery for FAI or labral tears, patient-reported outcomes postsurgery depended upon the pre-existing level of degenerative change in the hip before the surgery (5). Similarly, Minkara et al. (18) reported that preoperative osteoarthritis and joint space narrowing impact surgery success rate; yet, these authors contend that return to sport (RTS) is favorable after surgery. Furthermore, in a comparison of elite female and male competitive athletes, researchers examined athletes’ ability to return to competitive sports activity after arthroscopic surgery. More than 84% of females and 83% of males were able to return to competitive sport activity within 8 to 9 months (19). Additional discussion on RTS criteria was provided in an article by Reiman et al. (20) who contend arthroscopic hip surgery, which includes bony debridement and potentially labral reconstruction as an option to control pain and improve function in FAI patients, is still unclear. The authors conducted a meta-analysis using RTS criteria, defined as athletes returning to sport at or above the pre-injury level (20).
Although 35 studies were included in the analysis, authors deduced that there was poor outcome reporting on the ability of individuals with FAI to return to their respective level of athletic performance postsurgery. Such a gap in reporting of patient outcomes may make it challenging to formulate decisions about surgery. With the average RTS and activities after surgery being 7 months (20), more consistent reporting on RTS outcomes is needed. Nonetheless, Banerjee and McClean (8) contend that younger athletes may not have the option to discontinue sport or recreational activities, thereby increasing the likelihood for surgery.
Morphological correction and prevention of hip osteoarthritis are often primary reasons to support arthroscopy (21). However, exploration of nonsurgical approaches such as exercise intervention may improve motor control and hip stabilization strength to provide an alternative to surgery (11). Mansell et al. (19) compared arthroscopic surgery or physical therapy as a treatment for individuals who suffered with FAI in 80 (n = 80) active duty service members to determine differences in self-reported disability, costs, and ability to return to work (11). This randomized controlled trial with a 2-year follow-up reported no significant difference in outcomes between the two groups. Descriptive data in this study used the Hip Outcome Score, which uses a range of 1 to 100, with a lower score indicating a greater disability. However, the study presented limitations as several patients in the physical therapy group eventually had surgery (crossover effect), which reduced the number of participants in each group for comparison and the generalizability of the results. However, an individual dealing with FAI often has to weigh the pros and cons of surgery to nonsurgical treatment. Although surgery is on the rise for FAI, consistency in criteria for surgery along with patient variability indicates a need for further exploration into nonsurgical approaches in athletes and patients, such as focused exercise programming.
EXERCISE PROGRAMMING CONCEPTS
Hip pathologies are complex and it is possible for hip joint disorders to go undetected. Consequently, individuals may develop compensatory patterning that can lead to secondary symptoms (3,12). These symptoms may present as gluteal pain, for example. Even in patients diagnosed with FAI, compensatory patterning can have kinetic chain implications.
Diamond et al. postulate that persons with FAI who demonstrate compensatory patterning during activities of daily living could develop long-term unfavorable consequences (13). Participants with symptomatic cam-type or combined cam plus pincer FAI and age- and sex-matched controls without FAI underwent three-dimensional motion analysis during squatting tasks with analysis of the trunk, pelvis, and hip. Speed of descent was slower in the FAI participants.
During the constrained squat, individuals with FAI demonstrated greater pelvic rise and hip adduction on the symptomatic side. Researchers postulated that individuals with symptomatic FAI can squat to a depth comparable with controls, but there are problematic compensations, with greater ipsilateral pelvic rise and adducted hip position. Consequently, such alterations may put additional stress on adjacent regions of the body including increased load on the contralateral hip, sustained muscle weakness leading to suboptimal joint mechanics, and disruption to the hip's structural integrity (13). A systematic review of lower limb biomechanics recently published in the British Journal of Sports Medicine indicates similar trends (22). In the 14 studies analyzed, patients with FAI performed the squat to a reduced depth. They also demonstrated biomechanical impairments with walking, especially in hip extension and internal and external rotation (22). The altered hip biomechanics may be a strategy to reduce anterior hip activity during movement patterns and may be a maladaptive technique that reduces hip stability and integrity over time.
There are currently no validated formal exercise prevention programs for FAI (12,23). Conservative treatment relies on early identification and modifying lifestyle variables that may increase symptoms (12). Kolber et al. (15) indicate that FADIR, or combined movements of FADIR, can aggravate FAI. Consequently, exercise professionals should avoid prescribing exercises that could further perpetuate FAI aggravation (14). Impact activities such as running or jumping may need to be reduced or eliminated completely. Altering squats and lunges so as to avoid end range flexion also may be necessary. Even pivoting or turning toward the affected side, found in sports such as golf, or in the execution of certain agility drills, may need to be reduced or removed (15). Furthermore, additional lifestyle activities such as avoiding sitting in a cross-legged position, sleeping on one’s side with legs together, or staying in static postures for an extended period of time can be implemented to reduce FAI aggravation (15).
Wall et al. (21) contend that a well-constructed exercise program and activity modification may allow an individual with FAI to reduce symptoms, and potentially prevent future reoccurrence of symptoms (21). Interventions that include resistance training and focused stretching without aggravating symptoms can be an appropriate place to begin nonoperative treatment (15) (Table). Individuals with FAI should seek clearance from qualified medical personnel before beginning an exercise program. Palmer et al. believe that interventions to reduce cam deformity should commence before age 10 and may not be effective beyond skeletal maturity (7). This adds credence to the notion of addressing physical literacy early in the life span.
Four key goals in the exercise intervention are to:
- Improve postural alignment,
- Increase strength and endurance of core stabilizers,
- Increase strength and endurance of hip muscles, such as the gluteus medius, maximus, and minimus, and,
- Increase flexibility of lower body muscles that have hip and pelvis attachments.
In linking posture and the core to the hip, better postural alignment and core stabilization capability will minimize the stress on the hip flexor tendons. In addition, neutral posture also may reduce compensation patterns when the athlete or client is loading asymmetrically at the hip. Individuals with FAI can present a swayback posture and subsequent anterior pelvic tilt (15). The concept of “core” has many definitions, but exercises should include key musculature such as the diaphragm, pelvic floor, transverse abdominus, and multifidus. Pelvic floor strengthening has been used in a variety of pathologies (24) and also should be a staple in exercise programming for FAI. The gluteal musculature has key responsibilities in hip abduction and external rotation and may be weaker in individuals with FAI (15). Open kinetic chain exercises to strengthen the gluteal musculature can be progressed to close kinetic chain and functional activities in time. Flexibility and stretching of the hip without aggravated positions also are warranted; moreover, any of the example exercises should not reproduce pain.
In time, and in accordance with appropriate consultation, an individual could pursue returning to sport-specific tasks such as sustained jogging, running, cutting, and pivoting for at least 30 minutes without disruptive self-reported pain levels.
FAI has become a commonly recognized cause of limited hip range of motion and pain in adults and athletes (18). FAI can impact quality of life, reduce physical and recreational activities, and may warrant surgical intervention. Although arthroscopic surgery is on the rise as a treatment for individuals who suffer with FAI, nonsurgical approaches should be pursued. Exercise programming for nonoperative FAI should target improving postural stability, core stabilization, hip strength, and both static and dynamic mobility with an eventual goal of pursuing pain-free physical activity. The exercise professional can help individuals who suffer with FAI to optimize movement patterns, reduce compensatory tendencies, and potentially delay or detour surgical intervention.
BRIDGING THE GAP
Femoroacetabular impingement (FAI) is characterized by pathologic contact during hip range of motion, with aggravating movements most noted in hip flexion, adduction, and internal rotation. Hip impingement diagnoses and surgeries are becoming an increasingly prevalent concern with today’s athletes and general population. Exploration of nonoperative exercise interventions is warranted. Exercise professionals can safely improve postural alignment, core stabilization, gluteal activation, and range of motion in individuals with FAI.
The authors would like to thank Helena Norrstrom, Brittany Aubley, Linda Metts, and Micaela Lynch for providing photos and artwork to support this article.
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Keywords:© 2019 American College of Sports Medicine.
Cam-Pincer Impingement; Femoroacetabular Impingement; Hip Pathologies; Nonoperative FAI Treatment