You feel it in the front of your hip or deep in the groin, a pinching sensation when you sit for too long, pull your knee toward your chest, or rotate your leg inward. It builds gradually, often dismissed as a muscle problem or labelled vaguely as "hip tightness." In athletes, it surfaces as a loss of range, an inability to get into certain positions, or groin pain that doesn't quite resolve with rest. Femoroacetabular impingement syndrome (FAIS) is one of the most common sources of hip pain in active adults and adolescents, and one of the most consistently underdiagnosed. Understanding what it is, what drives symptoms, and what actually needs to be addressed, rather than what is most commonly assumed, is the starting point for getting on top of it.
What Is Femoroacetabular Impingement?
The hip is a ball-and-socket joint. Under normal anatomy, the spherical femoral head rotates smoothly within the cup-shaped acetabulum, with the labrum, a ring of fibrocartilage, sealing and stabilising the joint. In femoroacetabular impingement, abnormal contact occurs between the femoral head-neck junction and the acetabular rim during hip movement, particularly in positions of flexion and rotation. This repetitive abnormal contact damages the labrum and, over time, the articular cartilage, a process that, if untreated, can progress toward early-onset hip osteoarthritis. There are three morphological types:
- Cam impingement, the femoral head is not perfectly spherical. A bony prominence develops at the head-neck junction, typically on the anterolateral side. When the hip moves into flexion and internal rotation, this bump jams against the acetabular rim, generating shear forces that strip cartilage from the acetabular surface adjacent to the labrum. Cam morphology is more common in males and is significantly more prevalent in athletes, present in up to 55% of athletic populations compared to 14–24% of the general population.
- Pincer impingement, the acetabulum over-covers the femoral head, either focally or globally. As the hip flexes, the femoral neck contacts the acetabular rim prematurely, crushing the labrum in between. Pincer morphology is more common in women and is associated with a better long-term prognosis than cam, as cartilage damage tends to be less severe in isolated pincer presentations.
- Mixed impingement, the most common presentation overall, with both cam and pincer elements present simultaneously. Mixed morphology has been reported in 73% of cases in some studies and tends to produce more rapid joint damage than either type in isolation.
Critically, the presence of impingement morphology on imaging does not automatically mean symptoms. A high percentage of asymptomatic individuals have cam or pincer morphology on X-ray or MRI. FAI syndrome, the clinical entity that requires treatment, is defined by the combination of morphology, symptoms, and clinical examination findings. Imaging findings alone do not constitute a diagnosis.
FAI and Adolescents: Why This Matters
The relationship between adolescent sport participation and the development of cam morphology is one of the most important and least well-known aspects of this condition, particularly for young athletes and their parents. Cam morphology is not present at birth. The bony prominence develops during skeletal maturation, and the weight of evidence now supports that high-intensity sport participation during adolescence, while the growth plates of the proximal femur are still open, significantly increases the risk of developing it. The repetitive loading and rotational forces on the maturing physis drive aberrant bone formation at the femoral head-neck junction. Adolescent males participating in football, ice hockey, basketball, and similar high-load sports training three or more times per week are at particularly elevated risk. This does not mean adolescents should not play sport. The overwhelming benefits of physical activity far outweigh the risk. But it does mean that hip pain in an adolescent athlete should not be dismissed as "growing pains" or assumed to be a soft tissue problem without proper assessment. Early identification allows for appropriate load management and monitoring that may limit the severity of morphological change and reduce the risk of significant intra-articular damage developing. A study of adolescent FAI patients found that 82% demonstrated improvement in symptoms after two years of conservative management, reinforcing that early, appropriate non-operative intervention can be highly effective in this population. Up to 96% of adolescent FAI patients participate in organised sport, which underlines how central athletic activity is to both the development and the management of this condition in young people.
FAI and Hypermobility: A Complex Relationship
The intersection of FAI and generalised joint hypermobility (GJH) is clinically important and frequently overlooked in standard assessments. It might seem counterintuitive, impingement (too little room in the hip) alongside hypermobility (too much movement generally), but these two presentations frequently coexist and interact in ways that significantly complicate both assessment and management. In hypermobile individuals, the reduced passive stabilisation provided by lax connective tissue means the hip relies more heavily on active muscular control. When that muscular control is insufficient, which is the rule rather than the exception in hypermobility presentations, the femoral head is not well-centred within the acetabulum, allowing it to translate anteriorly and jam against the acetabular rim during flexion and rotation. This means that impingement symptoms in a hypermobile individual may be driven not primarily by bony morphology but by femoral head microinstability and inadequate dynamic stabilisation of the joint. The clinical implication is significant: aggressive stretching and joint mobilisation, which might be appropriate in a stiff, morphologically impinged hip, can be actively harmful in a hypermobile patient with impingement symptoms. Stretching an already lax capsule and over-mobilising an already poorly-controlled joint increases instability and amplifies the very mechanism causing pain. Hypermobile patients with hip impingement symptoms require a fundamentally different management approach: the emphasis must be on building the muscular control and dynamic stability that their passive structures cannot provide. Assessment must identify which component is dominant, morphological impingement or dynamic instability, to ensure the treatment is actually addressing the right problem.
Common Treatment Mistakes
Mistake 1, Treating the Imaging Rather Than the Patient
Because FAI is structurally defined on X-ray and MRI, there is a tendency to manage the image rather than the clinical presentation. Patients are sometimes told they have a "bone problem" that will inevitably require surgery, or conversely, that their scan "looks fine" when their symptoms are significant. Neither approach serves the patient well. The Warwick Agreement on FAI syndrome, the landmark international consensus statement, explicitly states that clinical diagnosis requires the combination of symptoms, examination findings, and imaging, and that imaging alone is insufficient. Cam morphology is present in a large proportion of asymptomatic people. The decision about treatment should be driven by the clinical picture, not by the alpha angle on a radiograph.
Mistake 2, Skipping Physiotherapy and Going Straight to Surgery
Hip arthroscopy for FAI produces good results, but it is not a first-line treatment and it does not replace the need for rehabilitation. The British Hip Society's 2024 physiotherapy guidelines and multiple NHS young adult hip referral pathways recommend that structured physiotherapy should precede surgical consideration in all but the most severe presentations. Well-designed conservative programmes have produced outcomes comparable to surgery in appropriately selected patients. More importantly, surgery that is not followed by comprehensive rehabilitation addressing the underlying strength deficits and movement pattern issues carries a high risk of symptom recurrence. Removing excess bone does not resolve the neuromuscular dysfunction that contributed to the problem, and those deficits will continue to load the joint adversely unless they are explicitly addressed.
Mistake 3, Stretching Into Pain
Patients with FAI frequently report being told to stretch their hip flexors and rotators more aggressively. In most cases, this is counterproductive. In cam impingement, stretching into hip flexion and internal rotation drives the femoral head-neck junction directly into the impingement zone. In pincer presentations, full flexion compresses the labrum. In hypermobile patients, as discussed above, stretching is potentially harmful. Stretching is not contraindicated in FAI management, but it must be applied selectively, within pain-free range, and targeted at structures that are genuinely restricted (often the iliopsoas, posterior hip capsule, and short external rotators) rather than used as a blanket approach.
Mistake 4, Ignoring the Lumbar Spine and Pelvis
The hip does not function in isolation. Lumbar spine mobility, particularly extension and rotation, directly influences the effective range available at the hip. When lumbar mobility is restricted, the hip compensates by moving into end-range positions more frequently and with less control. Similarly, pelvic tilt significantly affects the femoroacetabular relationship: anterior pelvic tilt increases effective acetabular anteversion and can exacerbate impingement in flexion. A comprehensive assessment that does not evaluate the lumbar spine, pelvis, and lumbopelvic control will miss clinically important contributors to symptoms.
Mistake 5, Underloading the Rehabilitation Programme
Conservative physiotherapy for FAI frequently fails not because the approach is wrong but because the loading is insufficient. A programme of gentle range-of-motion exercises and low-resistance band work does not produce the strength adaptations needed to meaningfully stabilise and offload the hip joint. The evidence for FAI rehabilitation consistently points toward progressive strengthening with meaningful resistance, weight-bearing, compound exercises that challenge the hip in the planes of movement that matter functionally.
What Needs to Be Assessed
Hip Morphology and Symptom Correlation
A clear understanding of the morphological type (cam, pincer, mixed) and how it correlates with the patient's symptomatic movements is the foundation of the assessment. The FADIR test (flexion, adduction, internal rotation) is the most sensitive clinical test for FAI and should be performed alongside FABER, internal and external rotation range assessment, and the quadrant test. Crucially, we assess whether these tests reproduce the patient's symptoms, a positive test is only meaningful when it mirrors what the patient actually experiences.
Strength Testing, Where the Real Work Begins
The neuromuscular profile of patients with FAI consistently reveals specific and significant strength deficits. A 2024 study demonstrated that even following hip arthroscopy and six months of rehabilitation, hip abductor and external rotator strength remained below pre-operative levels, confirming how difficult these deficits are to restore and how important it is to address them comprehensively. Deep hip external rotators, the piriformis, obturator internus and externus, gemelli, and quadratus femoris, are the primary dynamic stabilisers of the femoral head within the acetabulum. Their weakness allows excessive anterior femoral head translation and internal rotation, both of which drive impingement. These muscles are rarely specifically targeted in generic hip programmes and are among the most underdeveloped in FAI presentations. Gluteus medius and hip abductors, as in most hip pathologies, abductor weakness is a consistent finding in FAI. Weakness here contributes to pelvic drop during single-leg stance, altering the femoroacetabular contact mechanics with every step. The British Hip Society 2024 guidelines specifically recommend hip abductor strengthening as a core component of conservative FAI management. Gluteus maximus and posterior chain, weakness of the glute max contributes to overuse of the hip flexors and anterior structures, increased anterior pelvic tilt, and compensatory lumbar loading. Restoring gluteal dominance through hip extension is a fundamental component of rehabilitation. Hip flexors (specifically iliopsoas), in FAI, the iliopsoas is often overloaded as a compensation for posterior chain weakness, and its anterior pull on the femoral neck can contribute to anterior impingement. Assessment of both its strength and its length is important, tightness here increases anterior pelvic tilt and exacerbates the impingement position. Core and lumbopelvic stability, FAI rehabilitation that does not address lumbopelvic control produces inferior results. The ability to maintain a neutral pelvic position under load is the foundation upon which all hip-specific strengthening is built. We use hand-held dynamometry to quantify strength deficits objectively rather than estimating them, giving us precise data for each muscle group and a clear baseline against which to measure progress.
Movement Pattern Assessment
Beyond isolated strength, we assess how the patient loads and controls the hip during functional movement, squatting, single-leg stance, step-downs, and sport-specific patterns. Common findings include:
- Excessive hip adduction and internal rotation during single-leg loading, driven by abductor and external rotator weakness
- Anterior pelvic tilt under load, driven by hip flexor dominance and posterior chain insufficiency
- Excessive lumbar flexion substituting for hip flexion, a compensation that increases posterior hip loading
- Ipsilateral trunk lean during single-leg tasks, a compensation for hip abductor weakness identical to the Trendelenburg pattern seen in other hip pathologies
Hypermobility Screening
Every FAI assessment at IP Physio includes a Beighton score and a broader connective tissue assessment. As discussed, identifying hypermobility changes the management approach fundamentally, prioritising stability over mobility and avoiding techniques that would be appropriate in a stiffer, non-hypermobile presentation.
What the Rehabilitation Programme Targets
Phase 1, Education, Load Management, and Symptom Control
Understanding the condition, what FAI is, what does and does not cause pain, and what the long-term picture looks like, is a core part of early management. Patients who understand their condition engage more effectively with rehabilitation and make better decisions about activity modification. Load management means identifying the specific movements and activities that provoke symptoms and modifying them temporarily, while maintaining as much activity as possible. Deep hip flexion, prolonged sitting with hip flexion past 90 degrees, and activities involving repeated hip flexion and internal rotation are the typical provocations to manage initially.
Phase 2, Deep Hip Stabiliser and Posterior Chain Strengthening
This is where the rehabilitation substance lives. The programme targets:
- Deep external rotator activation and loading, clamshells with progressive resistance, hip external rotation in various positions, prone hip extension with rotation
- Gluteus medius strengthening, side-lying abduction, hip hikes, single-leg stance progressions
- Gluteus maximus loading, hip thrusts, Romanian deadlifts, step-up and step-down variations, single-leg press
- Iliopsoas eccentric control, controlling anterior pelvic tilt rather than simply stretching the hip flexor
- Core and lumbopelvic stability, dead bugs, pallof press, and functional progressions that challenge the ability to maintain pelvic neutral under load
For hypermobile patients, all exercises emphasise control and end-range stability rather than mobility, the goal is building the muscular tension that passive structures cannot provide.
Phase 3, Functional Loading and Movement Retraining
As strength develops, rehabilitation moves into weight-bearing, multi-joint loading that replicates the demands of daily life and sport. Single-leg squats, lateral step-downs, split squats, and sport-specific patterns are introduced progressively. Movement analysis at this stage ensures the patient is loading the hip correctly rather than reinforcing the compensatory patterns that contributed to the problem.
Phase 4, Return to Sport or Full Activity
Criteria-based progression, not time-based, guides return to full activity. Objective strength testing confirms that hip abductor, external rotator, and posterior chain capacity has reached appropriate thresholds relative to the contralateral side and to the demands of the patient's sport. For adolescent athletes in particular, load management guidance for return to sport is combined with monitoring of any ongoing morphological changes.
When Is Surgery Appropriate?
Conservative physiotherapy is recommended as the first-line treatment for FAI syndrome. It is effective for a substantial proportion of patients, particularly those with pincer or mixed morphology and without significant cartilage damage. Hip arthroscopy is considered when:
- Structured physiotherapy over a minimum of 3–6 months has not produced adequate improvement
- There is significant labral pathology or cartilage damage documented on MRI
- Cam morphology is severe and is mechanically restricting function in ways that cannot be compensated conservatively
- The patient's sport or occupational demands require a degree of hip range or load that cannot be achieved conservatively
When surgery is appropriate, physiotherapy before the procedure (prehabilitation), building as much strength and movement quality as possible before the operation, and comprehensive rehabilitation afterwards are both essential to optimising outcomes.
How IP Physio Can Help
FAI is a condition where getting the assessment right from the outset is what determines whether conservative management succeeds. We assess hip morphology in the context of clinical symptoms, screen for hypermobility and its influence on management approach, and use objective strength testing with hand-held dynamometry to quantify exactly which muscle groups need targeted development. Our rehabilitation programmes are progressive, weight-bearing, and functional, not generic band exercises, and are monitored with objective data at regular intervals. For adolescent athletes, we combine clinical management with practical guidance on sport participation and load monitoring. For patients who have had or are considering surgery, we provide both prehabilitation and post-operative rehabilitation guided by the 2024 International Society for Hip Preservation consensus guidelines. If you have hip or groin pain that has been vaguely attributed to tightness, or a scan report that has left you uncertain about what to do next, a thorough assessment will give you a clear picture of what is actually driving your symptoms, and a structured plan for addressing it. Get in touch with us today.
References
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