Psychological Factors in Chronic Pelvic Pain in Women: Relevance and Application of the Fear-Avoidance Model of Pain

Abstract

Chronic pelvic pain in women is a debilitating, costly condition often treated by physical therapists. The etiology of this condition is multifactorial and poorly understood, given the complex interplay of muscles, bones, and soft tissue that comprise the pelvis. There are few guidelines directing treatment interventions for this condition. In the last decade, several investigators have highlighted the role of psychological variables in conditions such as vulvodynia and painful bladder syndrome. Pain-related fear is the focus of the fear-avoidance model (FAM) of pain, which theorizes that some people are more likely to develop and maintain pain after an injury because of their emotional and behavioral responses to pain. The FAM groups people into 2 classes on the basis of how they respond to pain: people who have low fear, confront pain, and recover from injury and people who catastrophize pain—a response that leads to avoidance/escape behaviors, disuse, and disability. Given the presence of pain-related cognitions in women with chronic pelvic pain, including hypervigilance, catastrophizing, and anxiety, research directed toward the application of the FAM to guide therapeutic interventions is warranted. Isolated segments of the FAM have been studied to theorize why traditional approaches (ie, medications and surgery) may not lead to successful outcomes. However, the explicit application of the FAM to guide physical therapy interventions for women with chronic pelvic pain is not routine. Integrating the FAM might direct physical therapists' clinical decision making on the basis of the pain-related cognitions and behaviors of patients. The aims of this article are to provide information about the FAM of musculoskeletal pain and to provide evidence for the relevance of the FAM to chronic pelvic pain in women.

Chronic pelvic pain (CPP) is a prevalent, costly condition for which diagnosis and management often are difficult because of the complexities of causative factors and the multitude of involved structures. Chronic pelvic pain is defined as nonmalignant continuous or recurrent pain in structures related to the pelvis, lasting at least 6 months, and often associated with negative cognitive, behavioral, sexual, and emotional consequences. If nonacute and central sensitization pain mechanisms are present, then the condition is considered chronic, regardless of the time frame.¹ The multifactorial etiology of CPP contributes to the challenges of its medical and rehabilitative management and has been described as a medical “nightmare” for clinicians.² Chronic pelvic pain is not a disease; rather, it is a condition associated with dysfunction in one or usually more of the following body systems: gynecological, urological, gastrointestinal, musculoskeletal, and neurological (Table).² The community prevalences of CPP in the United States, United Kingdom, and New Zealand are estimated to be 14.7%, 24%, and 25%, respectively,^3–5 and an estimated prevalence of CPP in primary care of 3.7% is comparable to those for low back pain (4.1%) and asthma (3.8%).⁶ A recent study estimated the annual costs of endometriosis alone in 2002 to be $22 billion.⁷ In addition to the economic impact, CPP is costly in terms of emotional and psychological distress. Women with CPP are likely to report depression, anxiety, and sleep disturbances, in addition to limitations in sexual activity and mobility.^8,9

Table.

Organic and Nonorganic “Psychological” Causes of Pelvic Pain^a

^aReproduced with permission from Ghaly AF, Chien PW. Chronic pelvic pain: clinical dilemma or clinician's nightmare. Sex Transm Infect. 2000;76:419–425. Copyright 2000, BMJ Publishing Group.

In addition to specific organs, the following supportive structures may contribute to CPP: abdominal and pelvic-floor muscles (PFMs), ligaments, tendons, fascia, blood vessels, and peripheral and central nervous systems.¹⁰ Surgical procedures or any organic inflammatory process, such as endometriosis or irritable bowel syndrome, may result in scarring and adhesions, leading to pain in the affected viscera, pain in the PFMs, or both.¹¹ Pelvic-floor muscles affected by adhesions or inflammation caused by an organic (pathologic) process or surgery may spasm, become shortened, and have trigger points, all of which are believed to result in pain.¹²

There is evidence that CPP is associated with musculoskeletal pain in the PFMs¹³; therefore, physical therapists trained in pelvic-floor rehabilitation are increasingly being included as part of a multidisciplinary treatment approach to CPP.^14,15 Treatment interventions may include manual therapy of PFMs, electromyographic biofeedback, electrical stimulation, relaxation, and exercise. Although treatment approaches directed at improving physical impairments are fundamental in physical therapist practice, increasing evidence suggests that women with CPP may fare better with a treatment approach that incorporates cognitive-behavioral interventions directed at decreasing certain pain-related cognitions, including pain-related fear, pain-related anxiety, and catastrophizing.^16,17 These variables are the cornerstone of the fear-avoidance model (FAM) of musculoskeletal pain,¹⁸ a conceptual model that theorizes how particular psychological variables may contribute to the maintenance of musculoskeletal pain. The model was originally introduced to explain potential psychological causes of chronic low back pain,¹⁹ and other authors have since demonstrated how these psychological variables contribute to the maintenance of pain and disability in people with knee pain,^20–22 ankle pain²³ and, to a lesser extent, pelvic girdle pain.^24,25 Given the increasing evidence for the presence of the aforementioned psychological variables in women with CPP, using the FAM to identify women who may benefit from interventions that target psychological variables in addition to standard physical therapy interventions has the potential to improve the functional outcomes of women who have CPP and are referred to physical therapists. Therefore, the aims of this article are: (1) to briefly provide background information about the FAM of musculoskeletal pain and discuss its pertinence to other musculoskeletal conditions commonly treated by therapists and (2) to demonstrate the relevance of the FAM of pain to women with CPP to provide support for the use of physical therapist–directed interventions that target pain-related cognitions in women with CPP.

The FAM of Pain in Common Musculoskeletal Conditions

Lethem et al¹⁹ introduced the FAM as a theoretical model to explain why some people recover from a painful injury, whereas others who exhibit certain pain-related behaviors and cognitions develop chronic pain. The initial model was based on the central idea of fear of pain and was developed to provide an understanding of how exaggerated pain perception contributes to the maintenance of chronic pain problems, particularly low back pain. The model includes 2 extremes on a spectrum of coping responses to pain: confrontation and avoidance. People who confront pain adapt positively to an injury; they are motivated to return to their prior activities and view pain only as a temporary annoyance. People at the other extreme, who avoid pain, are motivated to avoid activities and experiences that they perceive as painful. This avoidance behavior is believed to lead to negative physical and psychological consequences, such as immobility and increased reinforcement of the discrepancy between pain sensation and pain experience and behaviors.

Other authors^18,26–28 further refined the FAM to include additional variables thought to contribute to the cycle of fear and avoidance behaviors exhibited in chronic pain disorders, including pain-related anxiety and pain catastrophizing (Figure). These 3 variables—pain-related fear, pain-related anxiety, and pain catastrophizing—are the central components of the current FAM and are believed to lead to avoidance/escape behaviors, disuse, and disability, placing an individual at risk for reinjury, perpetuation of negative pain-related cognitions and behaviors, or both.

Figure.

Fear-avoidance model of chronic pain. Reproduced with permission from Leeuw M, Goossens ME, Linton SJ, et al. The fear-avoidance model of musculoskeletal pain: current state of scientific evidence. J Behav Med. 2007;30:77–94. Copyright 2007, Springer Publishing Co.

Pain-related fear includes fear of the sensation of pain, fear of movement or reinjury, and fear of physical activities that are assumed to cause pain.²⁷ People with pain-related fear are likely to avoid activities or movements that they believe will cause pain, further exacerbating negative pain-related cognitions about these activities, disuse, and deconditioning. Pain-related fear is believed to contribute to the shift from acute low back pain to chronic low back pain,²⁸ and numerous studies have demonstrated the association of pain-related fear with disability in patients with chronic^27,29,30 and acute³¹ low back pain, hip and knee osteoarthritis,^32,33 and foot and ankle dysfunction.²³

Pain catastrophizing is used to describe how an individual responds to an actual or impending pain experience, and its presence is thought to be a risk factor for the development of chronic pain.^28,34 Catastrophizing involves the tendency to focus on the pain sensation (rumination), to exaggerate the threat of pain (magnification), and to negatively self-evaluate the ability to deal with pain (helplessness).³⁵ There is considerable evidence of the association between catastrophizing and pain intensity in acute³⁶ and chronic^32,34,37 pain conditions and between catastrophizing and physical and psychological disabilities.^28,32,38 In experimental settings, catastrophizing has been shown to be related to increased temporal summation of pain with thermal stimuli (increase in pain ratings in response to repetitive, low-frequency heat stimuli) for patients with chronic low back pain.³⁹ In that study, pain sensitivity was assessed with thermal stimuli at the forearm, a site distant from the low back, suggesting that overall pain sensitivity was enhanced in the patients who had catastrophizing thoughts about their pain. Pain catastrophizing also has been identified as a potential predictor of postoperative outcomes. Preoperative pain catastrophizing scores in patients who underwent total knee arthroplasty were used to predict short-term (6-week) and long-term (24-month) persistent postoperative pain^20,22; the results indicated that screening for catastrophizing before surgery may help identify patients who may be at risk for the development of chronic pain.

Pain-related anxiety is the third key component in the FAM of pain. Although the terms “fear” and “anxiety” are used interchangeably in the literature, pain-related anxiety is thought to be less intense than pain-related fear. Pain-related fear leads to defensive behaviors in the presence of a painful stimulus, whereas pain-related anxiety leads to preventive behaviors, including avoidance of and hypervigilance for perceived impending pain.¹⁸ People who are hypervigilant tend to direct their attention toward the potential threat of a painful stimulus while they disengage themselves from neutral stimuli. A recent study⁴⁰ examined the attentional bias toward different facial expressions in patients with chronic musculoskeletal pain, primarily of the upper extremity. Patients with chronic pain and high levels of fear of pain attended more to painful facial expressions, suggesting that the presence of fear mediated the attention to a painful stimulus. In a study of patients with fibromyalgia and temporomandibular joint disorder, amplification of a pressure stimulus occurred even at innocuous levels, suggesting that selective attention over time to a stimulus associated with pain (ie, to pressure in patients with fibromyalgia) will amplify pain intensity with a minimally noxious stimulus.⁴¹ These studies highlight the relationship between pain-related anxiety and pain-related fear, and they suggest that the presence of pain-related anxiety may blur the lines between an actual stimulus and an expected stimulus.

The presence of pain-related psychological variables has been shown to contribute to the maintenance of common musculoskeletal conditions managed by physical therapists. An emerging area of physical therapist practice is pelvic pain in women, and physical therapists are increasingly being included as part of a multidisciplinary team approach to the treatment of PFM dysfunction and pain. Next, we provide an overview of the etiology of CPP in women, present evidence for the presence of pain-related psychological variables in women with CPP, and theorize how the FAM of musculoskeletal pain may be pertinent to physical therapists' management of CPP in women.

CPP in Women

Organic Causes of Pelvic Pain

Gynecological causes of CPP include endometriosis and vulvar pain syndrome.^2,42 In endometriosis, endometrial tissues grow outside the uterus, typically on the ovaries or the pelvic peritoneum, and result in an inflammatory response associated with scarring, adhesions, fibrosis, decreased fertility, and pain.^43,44 The chronic pain symptoms typically associated with endometriosis include noncyclic or recurrent pain, dyspareunia, and dysmenorrhea.⁴⁵ Vulvar pain syndrome, or vulvodynia, is defined as vulvar discomfort, often described as burning pain, that occurs in the absence of physical findings or a specific, clinically identifiable neurological disorder.⁴⁶ Vulvodynia is classified by the location of the pain—generalized (entire vulva) or localized (eg, vulvar vestibule, clitoris)—and whether the pain is provoked (eg, penetration), unprovoked, or both. Numerous etiological factors are thought to contribute to this pain disorder; these factors include embryological abnormalities, hormonal factors, inflammation, infection, and neuropathic changes.⁴⁶

A common genitourinary cause of CPP is painful bladder syndrome, which is defined by the International Continence Society as the “complaint of suprapubic pain related to bladder filling, accompanied by other symptoms such as increased daytime and nighttime frequency in the absence of proven urinary infection or other obvious pathology.”⁴⁷ Although used interchangeably in the literature, painful bladder syndrome is different from its subcomponent, interstitial cystitis, which is a condition confirmed by specific histological and cystoscopic features of the bladder.⁴⁸ There is no diagnostic test or measure to validate the presence of painful bladder syndrome; rather, a diagnosis of painful bladder syndrome is based on a patient's symptoms. Pain complaints in women may involve structures of the lower urinary tract, vulva, vagina, or any combination of these. Painful bladder syndrome is more common in women,⁴⁹ with an estimated US prevalence of 25 to 30 million women.⁵⁰

Increasing evidence suggests that PFM dysfunction is associated with CPP.^51,52 In a recent study, Montenegro et al⁵³ found a significant difference between the prevalence of PFM pain in women with multiple CPP conditions and that in women who were healthy, suggesting a relationship between the presence of an organic pain condition and PFM pain. A 2010 systematic review⁵⁴ concluded that myofascial pain in the PFMs is associated with several different CPP conditions that occur in women; these include but are not limited to vulvodynia, endometriosis, and interstitial cystitis. Physical therapy interventions, such as electromyographic biofeedback, myofascial release of painful trigger points of the pelvic floor, and Thiele massage techniques, have been recommended for patients with secondary PFM dysfunction due to CPP conditions.^10,14,55,56 These recommended interventions, however, should be applied with caution because they are based on clinical expert recommendations, observational studies, or both.

Pain-Related Psychological Variables Associated With CPP in Women

In addition to the evidence of visceral and muscle pain in women with CPP, several studies over the last decade have begun to shift the focus from the biomedical mechanisms to the psychological variables associated with CPP and, specifically, how these variables may contribute to the maintenance of different types of CPP. In 1988, Kellner et al⁵⁷ demonstrated that levels of depression and anxiety were significantly higher in patients with pelvic pain and that these variables correlated significantly with hypochrondriacal beliefs. These authors suggested that the psychological distress associated with pain symptoms may have perpetuated the condition. More recent studies have examined the relationship of psychological variables with intercourse and sexual arousal. Payne⁵⁸ reported that women with vulvodynia reported more hypervigilance for pain during intercourse (dyspareunia), suggesting that increased attention paid to a threat of potentially painful stimuli during intercourse may have interfered with sexual arousal and diminished the experience of intercourse. Women with vulvodynia also reported more catastrophizing thoughts regarding intercourse-related pain than non–intercourse-related pain.⁵⁹ In a survey of women with interstitial cystitis,⁶⁰ a significant number of women with CPP complaints reported fear of pain during intercourse, compared with the results for women who were healthy; in addition, the women with CPP complaints had significantly higher reports of dyspareunia. A recent study⁶¹ examined the relationship of catastrophizing, hypervigilance, anxiety, pain self-efficacy, and pain-related fear with intercourse and induced pain in the vulvar vestibule. The data analysis revealed that catastrophizing was the only variable that contributed a substantial variance to intercourse-related pain, indicating that catastrophizing may play an important role in intercourse-related pain. Similarly, Granot and Lavee⁶² concluded that catastrophizing thoughts about pain were associated with dyspareunia in women with vulvodynia. Another key observation from that study was the lack of a correlation between the aforementioned psychological variables and pain at the vulvar vestibule with cotton-swab palpation; the authors attributed this finding to the relative nonemotional experience of this induced pain compared with the highly emotional experience of intercourse.

Other authors have used quantitative sensory testing, a method for quantifying pain sensitivity at local and distal locations relative to painful sites, to assess generalized pain hypersensitivity and the relationship of particular psychological variables with experimental pain. Granot et al⁶³ applied a series of thermal stimuli to the forearms of women with vulvodynia and women who were healthy. The heat pain thresholds of women with vulvodynia were significantly lower than those of women who were healthy, and the suprathreshold pain ratings and anxiety scores were significantly higher in women with vulvodynia. These results suggested that women with vulvodynia may have enhanced pain sensitivity, perhaps due in part to changes in central nervous system–mediated pain processing, which has been demonstrated in other populations with chronic pain.^39,64–66

Use of the FAM in Treatment Interventions for CPP

The available evidence suggests that psychological factors play an important role in the perception of pain, behaviors, and attitudes toward experimental and sexual stimuli in women with CPP. The psychological variables presented in the aforementioned studies are components of the FAM of pain; physical therapists should identify the presence of these variables with proper screening tools, and the presence of these variables should influence how treatment interventions are delivered in physical therapist practice.

In a 2003 clinical commentary, Bergeron and Lord⁶⁷ called for the integration of physical therapy and cognitive-behavioral therapy interventions for women with sexual pain disorders. Despite these recommendations, interventions that target psychological variables in women with CPP do not appear to be widely used by physical therapists to complement traditional physical therapy interventions. In a recent survey of physical therapists who treat vulvodynia,⁶⁸ 68% of the therapists agreed on 9 treatment modalities. All of these modalities focused on manual therapy and exercise of the PFMs and pelvic girdle, dietary modifications, and biomechanical correction of affected joints, but none targeted pain-related cognitions, such as fear of pain, catastrophizing, or anxiety about pain. The results of that survey suggested that although a majority of physical therapists who treat vulvodynia provide patient education about sexual dysfunction and the use of modalities (eg, vibrators, dilators) that may assist with such dysfunction and pain, specific cognitive coping strategies do not appear to be widely offered by physical therapists.

We believe that the physical therapy treatment interventions that have been shown to be useful in the treatment of PFM pain related to CPP^10,14,55,56 should be complemented with specific cognitive coping strategies. Cognitive coping strategies should include education about how certain psychological factors, such as catastrophizing, pain-related fear and anxiety, and attentional bias to pain during intercourse, may affect sexual function and the perception of pain during intercourse and other activities for which patients may report pain. Cognitive coping strategies also should include specific instruction about decreasing hypervigilance and expectation for painful stimuli during activities reported to cause pain and self-coping skills, such as relaxation training during periods of pain and gradual exposure to activities reported to cause pain. Given the previous identification of these psychological factors in women with CPP, the application of the FAM appears to be relevant and even necessary to achieving more desirable pain and sexual function outcomes.

The use of screening questionnaires such as the Pain Catastrophizing Scale,⁶⁹ the Fear of Pain Questionnaire,⁷⁰ and the State-Trait Anxiety Inventory⁷¹ at the initial physical therapy evaluation likely provides important information about the presence of psychological variables in patients referred to physical therapists for pelvic-floor rehabilitation; this information could alter the treatment approach used with patients. Additionally, these screening measures may signal the need for referral to another health care provider, such as a clinical psychologist or a sex therapist, in conjunction with physical therapy interventions. We recommend that screening for pain-related psychological variables be included as routine practice in the physical therapy evaluation and assessment of patients with CPP. Although these screening measures are used to identify the presence of particular psychological variables, the continued use of these measures over the course of treatment is important to assess whether changes in pain-related variables have occurred.

A well-designed trial of interventions for vulvodynia and associated dyspareunia randomized women diagnosed with these conditions to 1 of 3 intervention groups: group cognitive-behavioral therapy, electromyographic intravaginal biofeedback, and vestibulectomy.¹⁶ The 2 conservative interventions included some interventions commonly used by physical therapists, such as PFM exercises, electromyographic biofeedback, and vaginal dilation. In addition, the cognitive-behavioral therapy included education about vulvodynia, dyspareunia, muscle relaxation, Kegel exercises, and vaginal dilation. The goals of the cognitive-behavioral therapy were to reduce the fear of pain and other pain-related cognitions associated with intercourse, increase sexual activity level, and decrease pain. The electromyographic biofeedback intervention consisted of phasic and tonic PFM contractions followed by relaxation periods. The findings of that study indicated that all of the interventions resulted in positive sexual function and psychological adjustment outcomes, which continued to be maintained at the 6-month follow-up.

As suggested by Bergeron and colleagues^16,67 and demonstrated in another study,¹⁷ cognitive-behavioral therapy appears to be an effective treatment intervention for women with CPP, particularly vulvodynia, and many cognitive-behavioral interventions (eg, activity modification, relaxation training, education about the condition, and self-coping skills) are well within the scope of physical therapist practice.

Another type of treatment intervention that has been studied extensively in patients with low back pain is graded exposure to activities associated with pain-related fear, with the goal of encouraging patients to engage in the activities that they fear will cause pain. For women with CPP and resultant dyspareunia, one of these activities is often intercourse. To the best of our knowledge, there are no trials that compare the efficacy of a graded-exposure protocol with that of cognitive-behavioral therapy or other interventions for pain and sexual function in patients with CPP. For women with CPP, these protocols should be designed to include not just the simple vaginal dilation exercises that are typically used in clinical practice but also interventions that actually simulate intercourse.

In addition to rehabilitative interventions, collaborative psychosexual treatment of women with CPP is essential. Physical therapists trained in musculoskeletal dysfunction of the pelvic floor may include certain cognitive-behavioral interventions within their scope of practice, but referral to a sex counselor or therapist is recommended for women who have pelvic pain complaints and report sexual dysfunction or problems with intimacy due to those pelvic pain complaints. Sex therapists may be helpful in addressing low libido or arousal problems in addition to the effect of sexual dysfunction on intimate relationships.^15,72 Weijmar Schultz et al⁷³ advocated careful psychological assessment of women with CPP and recommended that psychotherapy be initiated first if signs of psychopathology are present.

There is evidence to suggest that women with CPP exhibit lower levels of sexual desire and arousal than women who are healthy.^74,75 Payne et al⁷⁴ reported that women with vulvodynia experienced more difficulty with sexual arousal, lubrication, and sexual desire than women without pain and that they had more catastrophizing thoughts and hypervigilance related to pain with intercourse. Brauer et al⁷⁶ used the threat of pain at a distal location (the ankle) during an erotic film clip to assess how fear of a painful stimulus may affect sexual arousal. Interestingly, there was no difference in the extent of decreased sexual arousal between women with dyspareunia and women without sexual dysfunction; both groups exhibited less arousal with the threat of a painful stimulus, suggesting that the threat of pain may decrease arousal even in the absence of reported sexual dysfunction. In a 2009 study, Brauer et al⁷⁷ assessed how an emotional appraisal of an event or experience would affect genital arousal. They reported that negative appraisals were associated with diminished arousal in both women with and women without dyspareunia. This result suggested that the negative emotional appraisal of an experience associated with pain, such as intercourse, may affect arousal in women despite their level of sexual function. These data suggest that in addition to screening for psychological variables in women with CPP, it may be worthwhile to ask patients about their levels of sexual desire and arousal, even if they do not report pain with intercourse.

Our recommendations for physical therapists' management of CPP begin with screening for the presence of psychological variables, including catastrophizing, fear, and anxiety. At present, there is no threshold or cutoff score for such measures related to CPP in women to indicate that patients may benefit from psychotherapy or sex therapy before or in conjunction with physical therapy. Physical therapy interventions should include education about patients' conditions and information about the presence of these variables and how they may affect patients' symptoms (eg, how selective attention to painful stimuli during intercourse may increase the perception of pain with intercourse). Self-coping skills, such as pain-relieving techniques or relaxation strategies, should be incorporated into treatment. Other interventions should target sources of musculoskeletal pelvic pain and may include manual therapy techniques, massage, and PFM relaxation or strengthening. Finally, multidisciplinary collaboration with other health care professionals, including but not limited to physicians, clinical psychologists, and sex therapists, will likely enhance the quality and scope of patient care.

Conclusion

The literature suggests that the psychological variables present in the FAM also are observed in women with CPP, suggesting the relevance of this theoretical model to women with CPP. A limitation of the generalizability of the FAM of musculoskeletal pain to CPP is the initiation of the fear-avoidance cycle and associated consequences. The FAM of musculoskeletal pain demonstrates that an injury leads to the pain experience; the aforementioned CPP conditions often are associated with some type of organic pathology that is longer lasting than an acute pain experience. Similarly, the consequences of pain-related psychological variables in musculoskeletal pain include disuse and disability. In women with CPP, the sequelae likely include sexual dysfunction and loss of partner intimacy. Another limitation of the FAM as related to CPP is that there is no indication that a causative structure exists, as demonstrated by Leeuw et al¹⁸ for the model specific to low back pain. For example, there is no evidence to support that catastrophizing leads to pain-related anxiety and fear of pain; it is possible that fear of pain, catastrophizing, and pain-related anxiety represent a cluster of psychological factors that are associated with CPP in women.

Isolated components of the FAM of pain have been studied in women with CPP, but an explicit application of the FAM to guide physical therapy treatment interventions is lacking. The presence of psychological variables may require cognitive-behavioral interventions that appear to correlate closely with interventions commonly practiced by physical therapists who treat women with CPP and associated musculoskeletal dysfunction of the pelvic floor.

There is a lack of controlled studies evaluating the efficacy of interventions aimed at decreasing certain pain-related cognitions. Future research should include randomized controlled trials that encompass more than just screening to determine whether pain-related cognitions change over time with a combination of rehabilitative, medical, and psychological interventions. In addition, future studies should compare the efficacy of traditional rehabilitative interventions for CPP in women with that of interventions that specifically target pain-related variables.