Pubic instability

Definition

Dysfunction or instability of the symphysis pubis (a subset of pelvic instability) is a condition that may cause chronic groin pain and is associated with a range of differing aetiologies that include sport-related repetitive micro-trauma that accelerates degeneration of the symphysial disc, high-energy direct pelvic trauma, low-energy pelvic ‘strains’ in individuals with pre-existing hypermobility, and parturition. In sport, this may limit athletic performance and is potentially career-ending.

Synonyms

Osteitis pubis, Athletic osteitis pubis, Pubalgia, Athletic pubalgia, Pelvic instability, Groin disruption injury.

Symptoms

As the clinical setting and underlying aetiology of pubic instability can be diverse, patients presenting with this condition include both sexes and vary widely in age. In sport, the typical patient is an 18-35 years old athlete (most commonly a male footballer) with chronic groin and/or lower abdominal pain that is poorly localised and associated with both pelvic impact loading and lower limb twisting & swing loading activities such as running, pivoting and kicking. The pain is gradual in onset, at first occurs only after exercise with associated stiffness but eventually develops as soon as exercise begins, is initially unilateral but eventually bilateral with broad distribution across the lower abdomen & groin, generally includes a midline component, and often radiates to medial thigh or perineum (Fig 1). Stiffness on getting out of bed the morning after sport is frequent. The symptoms may be aggravated by running, kicking, pivoting, pushing off, coughing, sneezing or sit-ups. Rarely, the patient may report ‘clicking’ on getting up from a chair, turning over in bed, or walking on uneven ground. There may be associated pain at one or both sacroiliac joints.

Fig 1. Location of ‘pubic instability’ pain

Physical findings

Physical examination findings are limited and variable. The most helpful findings are (a) tenderness in the midline directly over the symphysis pubis, and (b) a positive adductor ‘squeeze’ test (i.e. reproduction of pain with accompanying weakness when the adductors are isometrically contracted against a clenched fist held between the knees at varying degrees of hip flexion, Fig 2)[1]. Central groin pain may also be reproduced by ‘springing’ the symphysis (i.e. via direct pressure applied simultaneously to each pubic bone) or hopping on one leg. Frequent but less specific findings include tenderness over one or more of the para-symphysial tendons (conjoint, rectus abdominis or adductor longus) either unilaterally or bilaterally, pain to resisted sit-up, and pain to resisted hip flexion. Many patients also exhibit features of sacroiliac joint dysfunction, restricted internal rotation at the ipsilateral hip joint, and significant leg length discrepancy [2].

Fig 2. Adductor ‘squeeze test’ [source STMS]

Anatomy

The anatomy of the symphysis pubis and adjacent soft tissues is a key to understanding the pathology, clinical features and imaging findings that characterise pubic instability. The design of the symphysis is similar to the intervertebral discs of the spine, having a central disc of fibrocartilage that cushions against compressive loads, provides shock absorption and contributes to passive stabilisation (Fig 3). The articular disc often develops a central non-synovialised ‘primary cleft’ by the mid-to-late teen years that probably reflects a rising functional demand on the symphysis as loads increase and greater translational motion occurs. Similar to the intervertebral discs in the spine, the articular disc of the symphysis is also vulnerable to both degeneration and injury particularly when subject to violent or repetitive shear forces & torsion. Passive stability of the symphysis is further reinforced by a joint capsule comprised of: (a) the ‘superior pubic ligament‘, which extends laterally as far as the pubic tubercles, (b) an ‘arcuate’ ligament at the inferior margin, (c) a relatively thin & weak posterior capsule, and (d) a thin anterior capsule that blends inseparably with a very thick overlying sheet of aponeurotic tissue that, for want of a simple term, the author prefers to call the ‘pubic plate’ (alternatively the ‘pubic aponeurotic plate’). The pubic plate constitutes a central hub of mechanical linkage between the abdominal wall and the lower limbs (Fig 4). It is confluent with the external oblique aponeurosis, conjoint tendon, rectus abdominis tendon, pyramidalis muscle, inguinal ligament, adductor longus tendon, adductor brevis tendon, gracilis tendon and fascia lata of thigh. Viewed from the front, the anterior capsule of symphysis pubis is roughly triangular in distribution as it matches the related footprint of the anterior ‘facet’ of the pubic bone and, in skeletally immature subjects, also encompasses the pubic apophysis (Fig 5). The pubic plate linkages between abdominal wall and lower limbs provide a dynamic cross-brace for active stabilisation of the symphysis (Fig 6).

Fig 3. Symphysis pubis. A schematic diagram of the symphysis pubis in coronal-oblique cross-section (left) is shown with matching PD-weighted MR image (right). The central fibrocartilagenous disc (black arrow) shows a midline ‘primary cleft’ (vertical black line). This is sandwiched between layers of hyaline cartilage, which coat the articular cortex of the symphysis bilaterally (black arrowhead) but are too thin for standard clinical MRI protocols to resolve (thickness 200-400 µm in adults). The superior pubic ligament (white arrowheads) is very broad, extending between the pubic tubercles. White arrows indicate the arcuate ligament.

Fig 4. Anatomy of the pubic plate. The pubic plate is a thick wad of aponeurotic tissue that blends tightly with the anterior capsule and articular disc of the symphysis pubis (white arrowhead on anatomical drawing A and axial PD-weighted MR image B) and is comprised of both superficial and deep layers. The superficial layer (C) cross-links the external oblique to contralateral superficial fibres of adductor longus. With the superficial layer removed, the deep layer (D) can be appreciated as a structure of roughly pentagonal shape into which multiple structures insert, thus forming a central hub or “modiolus” (PM) of force transmission between the abdominal wall and lower limbs. Pubic modiolus linkages include the rectus abdominis tendon (RA), pyramidalis muscle, conjoint tendon (in this photograph located deep to, and obscured by, pyramidalis), inguinal ligament, deep fibres of adductor longus origin, anterior fibres of adductor brevis origin, upper fibres of gracilis insertion and a cord-like thickening of the fascia lata of the thigh (black arrowheads). Cadaveric dissection photographs and anatomical insights provided by Isaac Lui & Dzung Huu Vu (UNSW 2012).

Fig 5. Anterior facet of the symphysis pubis. Volume-rendered CT images of the male symphysis pubis are shown both (i) after the pubic apophysis has closed (left image, age 28), and (ii) before the pubic apophysis has closed (right image, age 21). The anterior pubic ‘facet’ is roughly triangular (arrowhead). Contained within this footprint is the attachment of the anterior capsule of symphysis pubis which is tightly blended to the overlying pubic aponeurotic plate. In skeletally immature subjects, the pubic apophysis is also a component of the anterior pubic facet, located along the anterior corner of the symphysis and shown most clearly on corresponding axial CT sections. This apophysis normally closes at age 20-26 years (males generally later than females). Note intra-articular extension of the physeal plate!

Fig 6. Active stabilisation of the symphysis pubis. The pubic plate is a hub or “modiolus” that links the adductor muscles & fascia lata of the lower limbs to the tendons & pyramidalis muscle of abdominal wall. This allows muscle co-contraction to actively stabilise the symphysis when walking, running, pivoting, etc. Correlated MR images show an oblique plane of section through the pubic plate (green lines in panel A) that provides an en face view of the plate and many of its attachments (hypointense central zone in panel B). Yellow arrows indicate the direction of pull of various muscles that insert at the pubic plate. Note the sum of the force vectors of the contracting abdominal muscles opposes the force vector of the contracting adductor muscles, thus forming a symphysial “cross-brace” (panel C). EO = external oblique. IO = internal oblique. TA = transversus abdominis. RA = rectus abdominis. ADD = adductor longus.

Pathology

Depending upon the particular anatomical structures that are most actively overloaded and symptomatic at any given point in time, the clinical and imaging features of pubic dysfunction or instability are variable. Although isolated para-symphysial tendonopathies and tendon injuries can and do occur, pelvic ‘dysfunction’ or frank pelvic instability is typified by multiple unilateral or, more frequently, bilateral co-existing pathologies (some of which may be asymptomatic) for which the single best unifying explanation is increased mechanical loading mediated by the central hub or cross-road of the pubic symphysis. ‘Dysfunction’ is a term used to describe the status of a joint with predominantly intact passive stabilizers that is able to maintain normal alignment despite applied stress but is nevertheless exposed to larger than normal stresses due to failure of the active stabilizers (also described as ‘failure of load transfer’ but, in the author’s view, better conceptualised as ‘micro-instability’). By comparison, true ‘instability’ exists when there is failure of BOTH the passive and active stabilizers of a joint, a condition in which applied stress is able to elicit frank joint mal-alignment. As true instability can be regarded as a higher grade of joint ‘dysfunction’, a more accurate descriptive term would be ‘macro-instability’. There are various pathways to pubic micro and/or macro-instability, including: (i) degeneration or tears of the articular disc, most common in sports such as football and hockey that repetitively subject the pubic symphysis to high torsional or shear loads; (ii) high-energy trauma to the pelvis which disrupts the symphysis, particularly crush and side-impact injuries; (iii) low-energy ‘strains’ of the symphysis in individuals with pre-existing hypermobility; (iv) isolated muscle or tendon injuries that create an imbalance of the normal forces that dynamically brace the pubic symphysis; and (v) parturition. Any of these pathways can, in turn, contribute to a vicious feedback cycle of further injury (Fig 7).

Fig 7. Aetiology of pubic instability. Pubic dysfunction or instability can have a variety of causes and a range of secondary effects (any of which may contribute to pain) that may form a vicious feedback loop and predispose to further injury. Macro-trauma may disrupt the articular disc & capsular ligaments of the symphysis, separate the pubic apophysis, or fracture the pubic bone(s). Repetitive micro-trauma may accelerate degeneration of the articular disc. A chronic force imbalance across the symphysis arising from asymmetrically increased loading or weakening of one or more the dynamic stabilisers may result in pubic instability. Other intrinsic factors that predispose to pubic instability include (i) leg length discrepancy of 5mm or more, which significantly increases loading on the shorter leg relative to the opposite side [20]; (ii) restricted hip joint range of motion, which can increase shear forces that act across the symphysis during activities that require maximal range; and (iii) ligamentous laxity in situations such as pregnancy, parturition and hypermobility syndromes.   

Sporting activities that typically place large adverse torsional and/or shear loads across the symphysis (e.g. ‘cutting’ and kicking in football, Fig 8) predispose to early degeneration with an associated loss of articular disc thickness and resilience, e.g. elite footballers, even in early adult life, often show features of premature osteoarthrosis [3]. An unstable symphysis further predisposes to a wide range of secondary mechanical effects, including: (a) pubic bone stress, manifesting variously as ‘osteitis’, stress fracture, or pubic apophysitis; (b) ‘tendonitis’ with or without complicating tendon tears involving any or all of the structures attaching at the pubic plate; (c) conjoint tendon dysfunction causing insufficiency of the posterior inguinal wall; and (d) a range of other features of pelvic instability more generally, e.g. sacro-iliac joint strain, ITB & gluteal tendinopathy, dynamic stretch-related irritation of various nerves that exit the pelvis (e.g. pudendal, lateral femoral cutaneous, sciatic). Although sacroiliac joint symptoms are generally not a striking feature of the condition, many patients will admit to low-grade pain or discomfort in the sacroiliac region if specifically asked.

Fig 8. Forces acting on the symphysis pubis. The symphysis is exposed to heavy compression loading, strong shear stresses and large torsional forces in many sports (e.g. when cutting or kicking in football). Green arrows indicate direction of weight force. Red arrows indicate direction of ground reaction force. Black arrows indicate direction of innominate motion and/or force vectors.

The significance of symphysial bone changes described as ‘osteitis pubis’ on x-ray, isotope bone scan & MRI has been debated. This uncertainty arises because the imaging findings do not consistently correlate with the presence, site or duration of pain [2, 4]. Use of the term ‘osteitis pubis’ is also problematic, as this lacks any agreed definition and does not infer any specific underlying pathology. It most often describes a clinical scenario of central groin pain with associated features of a tender symphysis, positive adductor squeeze test, and either pubic bone marrow oedema on MRI or increased radiotracer uptake on isotope bone scan (Fig X). However, bone marrow oedema is a non-specific finding which has a range of possible causes. At the symphysis, these include insertional tendinopathy, osteoarthrosis, avulsion fracture, symphysial diastasis injury or instability, pubic apophysitis, subchondral stress fracture, pubic insufficiency fracture, seronegative arthritis and infection. Thus, careful consideration must be given to the exact distribution of marrow oedema, the overall clinical context and any additional clues provided by accessory imaging features before the actual underlying pathology can be suggested.

In cases of pubic instability, the subchondral marrow changes observed on MRI at the symphysis are virtually identical to degenerative changes described by Modic in the spine at the vertebral end-plate, where the presence of low T1 and high T2 signal (Modic “Type 1” change) has an association with both disc-related pain [5-8] and active segmental instability [5]. The reported histopathology in spine includes disruption and fissuring of the chondral end-plate, vascular granulation tissue sprouting into the bone marrow, and reactive woven bone with thickened trabeculae [5]. Additionally, disc extrusions in the spine frequently contain fragments of hyaline cartilage avulsed from the end-plate [9-12], and the degree of end-plate marrow oedema correlates directly with the amount of avulsed chondral material [12]. In cases of pubic instability, where MRI often shows similar signal changes described as ‘osteitis’ at the symphysis, a corresponding mechanism of micro-fracturing along the pubic osteochondral junction secondary to chondral shear is therefore suggested. Another likely mechanism of marrow oedema at the symphysis is simple compression overload and, in the same way that MRI often shows marrow oedema at asymptomatic AC joints, this does not uniformly predict symptoms.

Imaging findings

At a minimum, the imaging diagnosis of pubic dysfunction or instability requires an appropriate clinical setting, an abnormal symphysis pubis, and associated para-symphysial tendonopathy. The pertinent information provided by imaging tests is summarised as follows:

1. Standing AP xray of pelvis

• Detect risk factor of leg length discrepancy (Fig 9);
• Assess the symphysis pubis and sacroiliac joints for premature degenerative change & evidence of chronic pelvic instability (Figs 9,12);
• Detect soft tissue calcification (e.g. at the adductor origin, Figs 9,10);
• Assist the exclusion of other causes of athletic groin pain (e.g. pelvic or proximal femoral stress fracture, hip joint dysplasia).

Fig 9. Indirect features of pubic instability. A standing AP radiograph of pelvis shows multiple findings associated with pubic instability, some of which infer underlying pelvic instability: (1) pelvic tilt secondary to leg length discrepancy; (2) degenerative changes at the symphysis pubis which include joint space narrowing, articular cortical irregularity and subchondral sclerosis; (3) slight pubic malalignment with associated traction osteophyte at the superior joint margin; (4) widening of the right sacroiliac joint inferiorly (arrowhead); and (5) ossification at the left adductor origin secondary to an old tear (arrow). Not all such changes are seen in every case.

Fig 10. Xray changes of pubic instability. Young adult footballer with marked irregularity of sub-articular bone density at the pubic symphysis that either reflects degenerative joint change or chronic pubic apophysial stress. Also note soft tissue calcification at the right adductor origin that could be secondary to either chronic ‘tendonitis’, previous adductor tear or avulsion of the pubic apophysis (arrow).

2. Flamingo stress views

Pubic instability is directly measured as the amount of vertical displacement observed at the symphysis on ‘flamingo’ stress radiographs:

Normal	< 2mm
Macro-instability	≥ 2mm
Micro-instability	< 2mm

As the aim of flamingo views is to assess passive ligamentous stability, optimal radiographic technique requires the patient to de-activate all dynamic stabilisers on the non-weight bearing side (see illustration). Note that pubic micro-instability falls within the range of normal variation and therefore cannot be diagnosed from flamingo views. Micro-instability must instead be inferred from secondary effects at the symphysis pubis (Figs 9, 16, 19, 20). Thus, the role of flamingo views is to:

• Detect pubic macro-instability (Figs 11, 12). This has valuable prognostic significance, as “the greater the instability, the more difficult to treat successfully” using physical therapy alone.

Fig 11. Pubic macro-instability. Flamingo stress views, obtained with the patient alternately weight-bearing on each leg, show significant displacement at the symphysis pubis (≥ 2 mm). Note underlying degenerative changes, which include a prominent subchondral cyst superiorly on the right. Image from: Atlas of Imaging in Sports Medicine.

Fig 12. Pelvic macro-instability. Flamingo stress views show (a) > 2 mm displacement at the symphysis pubis, and (b) associated widening of the left sacroiliac joint. Note subtle subchondral cystic changes indicative of degeneration at the symphysis.

2. High-resolution ultrasound

• Detect an abnormal symphysis pubis with features such as tenderness, capsular tear, mal-alignment, articular cortical irregularity, other degenerative changes (Figs 13,14);
• Detect changes of pubic apophysitis ± apophyseal separation (Fig 15);
• Detect para-symphysial ‘tendonitis’ ± tear at one or more locations (Figs 16, 17,18);
• Use real-time imaging and provocative stress to detect ‘Sports hernia’;
• Help exclude other musculoskeletal causes of groin pain (including acetabular labral tear, iliopsoas pathology, and non-athletic groin hernias).

Fig 13. Ultrasound of pubic instability. As demonstrated here, ultrasound is often more sensitive than xray for the detection of cortical irregularity. The transducer was angled obliquely from the sagittal plane in directions “a” and “b” as shown by arrows on the image at top right to obtain right & left “sagittal” views respectively on the image at bottom right. There is diffuse marked irregularity of articular cortex along both sides of the symphysis (arrowheads), either reflecting micro-avulsive injury at the osteochondral junction secondary to chondral shear or alternatively an irregular physeal plate secondary to pubic apophysitis. The joint is generally tender to probe when ‘osteitis‘ is symptomatic.

Fig 14. Pubic enthesopathy. A transverse ultrasound image obtained over the superior aspect of symphysis pubis shows marked enthesial bone surface irregularity corresponding with the left-side attachment of superior pubic ligament (solid arrowheads). Arrow indicates superior pubic ligament. Asterisk indicates pyramidalis muscle. Open arrowhead indicates inferior extension of conjoint and rectus abdominis tendons deep to pyramidalis muscle. Image from: Atlas of Imaging in Sports Medicine.

Fig 15. Ultrasound of pubic apophysitis. Transverse images of the symphysis pubis in an 18 year old footballer with right-sided groin pain show an irregular and widened physeal plate of right pubic apophysis (solid white arrow) when compared with the normal left side (arrowhead). Additionally, a thin echogenic line of non-displaced physeal separation complicates this case of apophysitis (stippled arrow). 

Fig 16. Para-symphysial tendonopathy in pubic instability. Comparison long-axis ultrasound images obtained over each adductor longus origin in a case of pubic instability show features of right-sided tendonopathy. Localised tenderness was elicited to probing over: (a) a hypoechoic thickened pubic plate & superficial-fibre component of adductor longus (arrow), (b) a hypoechoic thickened deep-fibre component of adductor longus (asterisk), and (c) enthesial bone surface irregularity at the pubic attachments of adductor longus and superior pubic ligament (arrowheads). Although unilateral in this case, such changes are more typically bilateral but asymmetric. Any preceding history of a significant episode of sudden-onset adductor pain which occurred under active athletic load would suggest a complicating partial tear, even if tear cannot be directly visualised by ultrasound. MRI is both more sensitive and more specific than ultrasound for adductor tears.

Fig 17. Ultrasound of adductor longus origin partial tear. A long-axis ultrasound image obtained at the pubic bone origin (P) of adductor longus tendon (t) shows a peel-back tear at the para-symphysial tendon-bone junction appreciated as a markedly hypoechoic or anechoic interruption of normal fibrillar echotexture (arrow). Para-symphysial tears that extend in continuity with the symphysial joint space are strongly suggestive of pubic instability. In this case, a longitudinal intrasubstance tear also involves the superficial tendon fibres (arrowhead). Image from: Atlas of Imaging in Sports Medicine.

Fig 18. Ultrasound of adductor longus ‘tendonitis’ with complicating insubstance tear. Coronal PD-weighted MR image (left) with correlating short-axis (top right) and long-axis (bottom right) ultrasound images of the adductor longus tendon origins. The right adductor longus origin shows asymmetric tendon thickening (black arrows) with subtle increased tendon signal on MRI and relative tendon hypoechogenicity on ultrasound indicative of tendinosis. Typically, as illustrated in this case, low-grade tendinosis is more conspicuous on ultrasound than MRI and, importantly, localised tenderness to probing over this point with the transducer also helps to confirm significance. Additionally, there is a small superimposed linear defect of complicating insubstance tear on both MRI and ultrasound (white arrowheads).

3. Isotope bone scan

• Detect increased radiotracer uptake of typical distribution at the pubic bone (Fig 19).
• Assist the exclusion of other musculoskeletal causes of groin pain (e.g. stress fractures, seronegative inflammatory arthropathy).

Fig 19. Isotope bone scan of pubic instability. Note the triangular distribution of increased radiotracer uptake at the pubic bone corresponds with the footprint of anterior pubic facet and marginates the symphysial joint line. Pelvic tilt is present. Image from: Atlas of Imaging in Sports Medicine.

4. MRI

• Detect signal changes of bone stress or ‘osteitis’ in the pubic marrow (Figs 22,23,24).
• Detect disco-capsular tear or ‘peel-back’ capsulo-periosteal stripping injury (also described as a ‘secondary cleft’) at the symphysis pubis (Figs 20,23).
• Detect changes of pubic apophysitis ± apophyseal separation (Fig 24).
• Detect para-symphysial ‘tendonitis‘ ± tear at one or more locations (Fig 23);
• Help exclude other causes of groin pain (e.g. hip OA, acetabular labral tear, iliopsoas pathology, stress fracture of the pelvis or proximal femur, other spine or pelvic pathology).

Fig 20. MRI of pubic instability. Sequential fat-suppressed PD-weighted coronal MR images of the symphysis pubis are shown. There is subtle pubic mal-alignment. The articular disc shows both a primary cleft (solid arrowhead) and a degenerative posterior protrusion (black arrow). A line of fluid signal extends laterally from the primary cleft beneath the left adductor longus tendon origin (white arrow), described in the radiology literature as a “secondary cleft” but better regarded as a peel-back periosteal stripping tear of the anterior capsule of symphysis which partially involves the intimately related adductor longus origin (and, in the author’s opinion, is pathognomonic of pubic instability). In this case the smoothly marginated tear plane and lack of surrounding soft tissue swelling/hyperintensity indicates a ‘non-acute’ injury. No significant sub-articular marrow hyperintensity is seen to suggest active ‘osteitis’ in this case. Asterisk indicates left adductor longus tendon.

Fig 21. MRI of pubic instability. Sequential fat-suppressed PD-weighted axial MR images of the symphysis pubis show a primary cleft within the articular disc (solid arrow) with second thin hyperintense line of fluid-equivalent signal extending along the osteochondral junction of symphysis pubis on the left side (indicative of chondral shear injury, solid arrowheads) that communicates with the primary cleft and also involves the para-symphysial portion of left adductor longus origin (indicative of tear, open arrowhead). The anterior pubic facet shows very mild enthesial marrow hyperintensity, but no significant sub-articular marrow hyperintensity is seen to suggest active ‘osteitis’. Asterisk indicates left adductor longus tendon.

Fig 22. Instability-related changes in sub-articular marrow on MRI. Matching coronal T1 and fat-suppressed PD-weighted MR images demonstrate sub-articular marrow changes of symphysial degeneration. Note different areas of subchondral sclerosis (black arrow), fatty change of Modic Type 2 signal abnormality (white arrowheads), and marrow hyperintensity of Modic Type 1 signal abnormality indicating active ‘osteitis’ (white arrows). These changes are bilateral but asymmetric. Image from: Atlas of Imaging in Sports Medicine.

Fig 23. MRI of pubic instability in an athlete. Fat-suppressed axial (top) and coronal (bottom) PD-weighted MR images demonstrate marrow hyperintensity of active ‘osteitis’. Note the distribution of abnormal marrow signal: bilateral, slightly asymmetric, marginating both the symphyseal joint line & anterior pubic facet. Other features in this case include (a) a degenerate articular disc with posterior bulge (arrow); (b) anterior capsulo-periosteal stripping at the symphysis which involves the adductor longus origin (black arrowhead); and (c) right adductor longus origin ‘tendonitis’ (white arrowhead).

 Fig 24. Pubic stress fracture. Xray shows localised sub-articular sclerosis along the inferior half of symphysis on the left side. Corresponding fat-suppressed coronal PD-weighted MR image shows a corresponding hypointense fracture line (arrowed) with surrounding marrow oedema. 

Diagnosis

The differential diagnosis of chronic athletic groin pain is wide (Fig 25) and clinical evaluation therefore requires a careful synthesis of history taking, physical examination and appropriately directed investigation. Isolated muscle and/or tendon injuries are not uncommon and must be differentiated from, not confused with, a background setting of pubic instability in which multiple co-existing abnormalities are typically found. It is also important that both the radiologist and sports physician remain alert to the possibility of an underlying seronegative spondylarthropathy (e.g. ankylosing spondylitis), as an early diagnosis allows appropriate disease-modifying drug therapy. Clinical ‘red flags’ for spondylarthropathy include a positive family history, persistent low back or buttock pain with associated morning stiffness that lasts more than 1 hour, and concurrent skin or eye symptoms.

Fig 25. An abbreviated list of causes for chronic athletic groin pain

At a minimum, a diagnosis of pubic instability requires: (a) an appropriate clinical setting; (b) an abnormal symphysis pubis; and (c) an associated symptomatic para-symphysial tendonopathy that is usually multiple. In our clinic, the routine imaging work-up of chronic groin pain includes: (1) functional (weight-bearing) radiographs of the pelvis comprised of standing AP and ‘flamingo’ stress views to assess alignment and directly measure motion at the symphysis pubis, evaluate the hip joints, screen for stress fractures and unsuspected bone pathology, and detect soft tissue calcifications; (2) high-resolution real-time ultrasound examination to assess the conjoint tendons, dynamically assess the straining inguinal canal, and identify specific anatomic sites of tenderness; and (3) MRI to assess the symphysis & supporting ligaments, pubic bones and pubic apophyses, adductor origins, rectus abdominis insertions and pyramidalis muscles (at the same time providing a limited assessment of the hip joints, iliopsoas structures and obturator nerves).

Treatment

Although any of the secondarily affected para-symphysial structures may be the dominant source of pain at presentation, the main goal of treatment is to restore pelvic stability. This primarily involves a physical program of graduated core strengthening that requires pain-free exercise and is guided by an absence of pain to key clinical provocation tests (Fig 26). Although some athletes are able to continue playing while still achieving a slow resolution of the condition, this carries several risks which include increased time to resolution, a further loss of ligamentous competence, and sudden breakdown due to complicating tendon tear. For the athlete who cannot or will not suspend competition to follow an appropriate physical therapy program, symptoms may be temporarily suppressed by using (a) corticosteroid therapy, administered either as short oral course or more directly by injection of the symphysis pubis [13], and (b) the use of compression shorts which improve pelvic support and have been shown to reduce pain during exercise [14].

Fig 22. Physical therapy for pubic instability. An example of physical therapy for pubic instability is shown. Therapy commences at 12 o’clock and progresses in a clockwise direction. The circle shows that at any stage, depending on progress, an athlete can move either forward or backward. In the centre are the baseline clinical tests (including pubic symphysis stress tests) that are used to assess an athlete’s ability to transfer load without pain/discomfort. Until these are negative, the athlete should not be allowed to progress. As pain-free function is achieved at each milestone, the rehab program progresses from initial straight linear to controlled lateral and eventually uncontrolled movements. A chart of this kind offers a standardised conceptual framework for meaningful communication between all parties – sports physician, physiotherapist, trainer, strength & conditioning coach – involved in the care of an athlete. With permission from Anna-Louise Bouvier & Dr Sharron Flahive.

If the response to an adequate 3 – 6 months trial of conservative physical therapy is poor, a variety of surgical procedures have been described. These include adductor tenotomy & conjoint tendon repair [15], arthrodesis or debridement of the symphysis [16], and placement of laparoscopic pre-peritoneal mesh to brace the symphysis [17]. Rigidly fusing the symphysis can lead to significant symptoms of sacroiliac joint overload and is rarely performed in athletes. However, the use of laparoscopic mesh offers an exciting new surgical option that can improve passive stability without rigidly fixing the joint and compromising its essential role in pelvic shock absorption. In the author’s view, adductor tenotomy may also be counterproductive in the longer term if this serves to exacerbate the fundamental underlying problem of pubic dysfunction or instability by further weakening the dynamic cross-brace mechanism that normally stabilises the symphysis. Experimental treatments include intravenous bisphosphonate drug therapy [18] and symphysial prolotherapy [19,21], but experience with these remains limited and their role is uncertain.

Acknowledgement

The author thanks Dr Ken Crichton, Sports Physician, North Sydney Sports Medicine Centre, for his expert clinical advice.

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