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Picture of a pelvis with arrows describing the inter-relationships between the hip and pelvis

The hip and pelvic floor are commonly assessed and treated as disparate entities. Pelvic health (women’s and men’s health) physiotherapists tend to specialise in this area, with the assessment and treatment focus understandably on intra-pelvic mechanisms. Other musculoskeletal or sports health professionals are usually very happy to ‘leave that to the pelvic health physio,’ content to push on with managing extra-pelvic mechanisms. But of course, within one individual’s pelvis, what happens inside can influence extra-pelvic symptoms and dysfunction, and vice versa. Is there enough awareness, communication and co-development of management strategies that consider both the internal and external pelvic environment? Often this is not the case. Pelvic health physio’s might be prescribing exercise to relax and lengthen a hypertonic pelvic floor, but these exercises can be provocative for a concurrent hip pathology … which itself may be contributing to the pelvic floor dysfunction. The MSK/sports health professional may also be prescribing hip exercises that the pelvic health physio has determined are inappropriate for the patient’s pelvic floor. This type of situation can be extremely confusing and frustrating for the patient, with effectiveness of both interventions likely to be negatively impacted. For the sake of our patients presenting with hip and pelvic floor conditions, let’s get it together!

Join me on this journey of exploring the connections between the hip and pelvic floor.
Here’s what we’re going to talk about:

  • The pelvic floor and its anatomical relationship to the hip muscles
  • Interactions between pelvic floor and hip muscle function in healthy individuals
  • Hip function in those with pelvic floor dysfunction
  • The effect of training hip muscles in those with pelvic floor dysfunction
  • The effect of hip osteoarthritis and hip replacement on pelvic floor dysfunction
  • Considerations for co-treatment of hip conditions and pelvic floor dysfunction

The pelvic floor and its anatomical relationship to the hip muscles

Pelvic floor capacity. Can the pelvic floor go it alone?

No ‘person’ is an island. The pelvic floor is not a little island state within the pelvis - it has important connections to ‘the outside world’ that exists in the extra-pelvic environment. Compared with other skeletal muscles, the pelvic floor musculature is relatively thin, with small physiological cross-sectional area (PCSA) - the predictor of force generation.1 For example, the lumbar multifidus has a mean PCSA of 23.9 cm2, which is more than 30 times the PCSA of the pelvic floor muscles. While the healthy pelvic floor has the capacity to resist intra-abdominal pressure exerted by low load activities of daily living, such as standing and sitting, these muscles alone are unable to generate enough tension to withstand forces imposed by more challenging tasks such as a voluntary cough, a weighted squat (15kg) or jumping.1 The additional support to meet these higher demands is proposed to come from non-contractile connective tissue elements, fascial attachments and extra-pelvic muscle attachments, primarily contributions from the obturator internus muscle.1

The pelvic floor and obturator internus

There is a growing interest in the relationship between the hip and pelvic floor, with the obturator internus muscle a key focus due to its strong structural relationship with the pelvic floor musculature. The obturator internus muscle lines the inner surfaces of the lower pelvis, originating from the obturator membrane and ischiopubic ramus. It exits the pelvis via the lesser sciatic foramen, collects the inferior and superior gemelli, transits across the back of the hip joint to insert onto the medial surface of the greater trochanter of the femur. This muscle is a deep hip external rotator, and also an abductor in a flexed hip position.2 The obturator internus is thought to provide important posterior support for the hip joint and may also have a role to play in augmenting pelvic floor muscle function, due to its strong connections to the arcus tendinous musculi levatoris ani (ATLA). This is a broad aponeurotic sheath that acts like a suspension bridge, spanning from the pubic bone anteriorly to the ischial spine posteriorly, on each side of the pelvis. This fascia is bound down to the underlying obturator internus muscles and provides an important lateral origin for the levator ani muscles of the pelvic floor.3

MRI Scans showing the anatomical relationships of the hip and pelvic floor

Interactions between pelvic floor and hip muscle function in healthy individuals

A number of studies have explored the relationship with hip and pelvic floor muscle function in healthy individuals with no known hip or pelvic dysfunction.

Immediate effects of hip muscle contraction on pelvic floor muscle behaviour

One study by Amorim and co-authors measured pelvic floor force production with an intravaginal dynamometer during 3 different tasks in crook lying - i) isolated pelvic floor muscle contraction, ii) pelvic floor muscle contraction combined with hip abduction (30% and 50% maximum hip force), and iii) pelvic floor muscle contraction combined with hip adduction (30% and 50% maximum hip force).4 The tests were conducted on 20 healthy, nulliparous women, aged 27.2 ± 5.3 years. They reported that isometric hip adduction or abduction combined with pelvic floor muscle contraction did not significantly increase intravaginal force production or endurance and therefore concluded that the use of hip co-contraction was not justified for training programs aiming to improve pelvic floor muscle strength and endurance.

Similarly, Wang and colleagues (2021) measured lift of the bladder base on suprapubic ultrasound to assess pelvic floor function during 3 conditions – i) an isolated active pelvic floor contraction, ii) an isometric external rotator contraction at 50% of maximal force and iii) concurrent active pelvic floor and external rotator contraction, in 13 healthy adult women (mean age 23.8 ± 2.8 years). The test position was a crook lying position with hips bent 45° and in a ‘v shape’ – knees apart, heels together and toes out.4 They reported that the isolated isometric hip external rotation at 50% of a maximal contraction produced a mean 2.4 ± 0.48mm lift of the bladder base, without conscious activation of pelvic floor muscles. However, the finding that conscious activation of the pelvic floor muscles alone produced greatest lift in the bladder base, led them to conclude that the use of hip external rotation in pelvic floor muscle training is not justified for improving pelvic floor muscle strength.4

However, what is common to both the above studies is that the participants had to focus on keeping hip muscle force production to 30% or 50% of a maximal muscle contraction, by either matching their effort to a visual force trace3 or a dynamometry reading.4 Force matching involves considerable focus and load on the nervous system and may have impacted on co-contraction intensity of the pelvic floor musculature.

Another study of 21 women (43.7 ± 11.3 years) assessed pressure generated by the pelvic floor during contraction of the hip internal rotators, external rotators, abductors, adductors and the gluteus maximus in supine.6 They found that hip muscle activation only resulted in pelvic floor muscle pressures of around 30% or less of that generated by focused conscious contraction of the pelvic floor musculature. The intensity of hip muscle contraction was not stated, so it is unclear if the hip exercises were maximal contractions or not. The authors concluded that training of hip muscles alone would be insufficient to activate the pelvic floor sufficiently to illicit a training effect and could not be recommended.6

Training effects of hip muscle strengthening on pelvic floor muscle function

Tuttle and colleagues investigated the training effects of external rotator strengthening pelvic floor muscle force.7 Forty healthy nulliparous women, aged 18 to 35 years, were randomly assigned to either an exercise group or a control group. The exercise group performed hip external rotator strengthening 3 days/week for 12 weeks in sidelying and standing.  Pelvic floor force production, as measured by a Peritron perineometer (a vaginal pressure sensor) increased by almost 50% after this training period, and external rotator strength increased by around 20%.7 The mechanism underlying the changes in pelvic floor strength cannot be clearly determined. Did strength increase due to improved strength of the obturator internus muscle? There were of course other muscles working during these exercises, with high likelihood of pelvic floor muscle co-activation, but this was not measured. Participants were not instructed to co-contract their pelvic floor muscle, but automatic co-contraction particularly with weightbearing exercise is likely to have occurred. It was also not possible to blind participants to the fact that pelvic floor muscle function was a key interest of this study.

Hip function in those with pelvic floor dysfunction

What do we know about hip function in those with pelvic floor dysfunction? Is there a relationship?

In a case-controlled study of 42 women (21 pairs), those with urgency or frequency were found to be significantly weaker in their hip abductors and external rotators on dynamometry than women without lower urinary tract symptoms. However, there were no between-group differences in pelvic floor strength or endurance measured via vaginal manometry (an internal sensor).8 Similarly, Hartigan and colleagues (2019) found that women with stress urinary incontinence had lower hip external rotation and hip abduction strength than women without stress urinary incontinence.9 These differences were large in magnitude and likely clinically meaningful: hip abduction deficits of 40.9% and 32.1% (dominant and non-dominant limbs) and external rotator deficits of 15.9% and 18.0% in the group with stress urinary incontinence. They also found that there was no difference in pelvic floor muscle performance between the groups. Not that those with stress urinary incontinence had good pelvic floor muscle function, but that the control group had similar deficits. The majority of participants could not sustain a pelvic floor muscle contraction for 10 seconds and had power ratings of 3+ or less on internal assessment.9

The relationship between hip and pelvic floor muscle dysfunction is unclear.

Are those with pelvic floor muscle dysfunction able to reduce chances of developing symptoms of urinary incontinence if their hip muscle function is adequate? Is better obturator internus function compensating for the pelvic floor deficits? Do those with better hip muscle function move in ways that are less likely to result in acute loads on a deficient pelvic floor, and subsequent urgency or stress urinary incontinence? Is it simply association rather than causation?

The effect of training hip muscles in those with pelvic floor dysfunction

If there is a relationship between hip and pelvic floor muscle function, can we improve pelvic floor dysfunction by improving hip muscle function?

Jodre and co-authors compared a seated resisted hip rotation strengthening program, with a seated pelvic floor muscle training program in 27 women with stress urinary incontinence (age 53.87 ± 12.75 years).10  They found similar improvements in symptoms of stress urinary incontinence in both groups, with the hip training group showing a slightly quicker improvement in reported leaks per week. Another study assessed the ability of a hip exercise program to improve intravaginal squeeze pressure in 25 older women (66.31 ± 14.69 years) with or without stress urinary incontinence.11 Participants undertook 12 weeks of concentric, isometric, and eccentric training of the hip external rotators, without instruction to include pelvic floor muscle contraction, performed 3 times per week. Together with improvements in hip external rotator strength, participants exhibited an average of around 35% improvement in intravaginal squeeze pressure, with the authors concluding that ‘hip external rotation exercises may be effective as an indirect form of pelvic floor muscle exercise.’

Another randomised clinical trial compared the effect of pelvic floor strengthening alone with pelvic floor strengthening plus hip exercises, on symptoms of stress urinary incontinence and pelvic floor muscle function.13 Hip strengthening included exercises for the gluteals and hip adductor muscles. The group who performed both hip and pelvic floor muscle training (n=22), reported better improvements in frequency of daily urine loss than those who performed pelvic floor training alone (n=21), although there were no between-group differences in improvement of pelvic floor strength.  This indicates that improvements in stress urinary continence were not moderated solely by improvements in pelvic floor muscle strength.

The effect of hip osteoarthritis and hip replacement on pelvic floor dysfunction

It seems that those with lower urinary tract conditions may have dysfunction of their hip musculature. So, do those with hip conditions have lower urinary tract symptoms and does treatment for hip conditions alter these symptoms?

There is little evidence available on prevalence of pelvic floor dysfunction and lower urinary tract symptoms in those with hip osteoarthritis, but the information that is available suggests that this is likely to be a common problem, at least for females (unfortunately it seems information is only available for females). Tamaki and colleagues (2014) reported 41% (81/189) of females in their prospective study of patients presenting for total hip arthroplasty reported symptoms of urinary incontinence.13 Another recent prospective study reported a similar prevalence of 38% (70/183) of women presenting for total hip arthroplasty who had symptoms of urinary incontinence, defined as a score of ≥1 on the International Consultation on Incontinence Questionnaire—Short Form (ICIQ-SF).14

Both papers suggested that there may be a link between urinary incontinence and hip osteoarthritis, mediated by atrophy of the obturator internus muscle, which is common in those with hip OA, and a change in position of the hip joint. A more externally rotated position of the hip may reduce tension in the obturator internus, thus reducing its ability to assist in force transfer of the levator ani muscles.

MRI and CT Scan of Obturator Internus in Hip OA and after Hip Replacement

Evidence of post-operative changes in urinary incontinence have also been evaluated to support this link. Tamaki’s paper reported symptoms of urinary incontinence were improved in 64% of their patients following total hip arthroplasty, using a direct anterior approach.13 Baba and co-investigators compared the effects of anterior approach and posterior approach total hip arthroplasty on preoperative urinary incontinence in 76 female patients.15 Urinary incontinence improved after surgery in eight patients (22.2 %), slightly improved in one (2.8 %), remained unchanged in 26 (72.2 %), and was slightly aggravated in one (2.8 %) in the anterior approach group. In the posterior approach cohort, urinary incontinence improved after surgery in one (2.5 %), remained unchanged in 30 (75 %), slightly aggravated in four (10 %), and aggravated in five (12.5 %). Their conclusion was that while anterior approach surgery improves urinary incontinence, a posterior approach is more likely to aggravate the condition, due to disturbance of the obturator internus tendon which is detached and then repaired during surgery.15 However, the recent study by Martines and colleagues (2022) reported significant improvements in urinary incontinence following posterior approach arthroplasty in their overall sample and in the subgroup with preoperative urinary incontinence (≥1 ICIQ-SF).14 There has certainly been closer attention in more recent times to achieving superior repair of the posterior capsule and deep external rotators with the aim of reducing risk of posterior dislocation with posterior approach surgeries. These risks do appear to have reduced,16 so perhaps there has been an additional benefit in restoring superior function in the pelvic floor.

How exactly does hip arthroplasty improve urinary incontinence?

Improvement in strength of the atrophied/inhibited obturator internus following arthroplasty has been suggested as an important mechanism. Changes have been reported to occur rapidly, so muscle hypertrophy may not be the primary or only mechanism. A Japanese study assessed the impact of anterior approach total hip arthroplasty on urinary incontinence in 50 patients who were determined to have both hip osteoarthritis and Stress Urinary Incontinence (SUI), Urge Urinary Incontinence or Mixed Urinary Incontinence (MUI).17 Three months after hip replacement surgery, 36 of the 50 patients (72%) reported improvement or complete resolution of their urinary incontinence, with best outcomes for MUI and SUI.

Interestingly, improvements were reported as quickly as 3 days post-surgery.17 It is possible that the removal of the nociceptive joint structures may immediately reduce arthrogenic inhibition of the obturator internus. Alternatively, or additionally, the authors suggested that early changes may be related to an immediate change in tension of the obturator musculotendinous structure. This may be due to cup offset, stem length or stem placement and the relative trochanteric offset. Pelvic floor function may be positively impacted very quickly if the obturator internus has been relatively pretensioned by structural changes imposed by total hip arthroplasty.

Does this mean that early hip replacement for females with osteoarthritis may be warranted as a treatment for urinary incontinence??? Well, no! But the relationship is strong enough for us to take away some key learnings...

Key Learnings:

  • Dysfunction in the posterior hip cuff, likely particularly in the obturator internus, may impact on urinary incontinence in those with hip osteoarthritis (at least in females but keep an eye out for links in males as well)
  • Targeted treatment to optimise function and health of the OI may assist in management of urinary incontinence
  • Reducing pain and maintaining as much rotation range as possible, particularly avoiding excessive hip external rotation in habitual postures and movement patterns, may assist in optimising obturator internus contribution to pelvic floor function
  • Targeted assessment and training of the deep hip rotators after total hip replacement may provide not only gains in hip function but assist in reducing symptoms of urinary incontinence.

Considerations for co-treatment of hip conditions and pelvic floor dysfunction

Can we take from the information presented above that by strengthening and upregulating the activity of the hip musculature (particularly the external rotators), we will have a consistently positive effect on pelvic floor function and lower urinary tract function?

Well, no! The relationship does not appear to be quite that simple. It never is, is it?!

Hypertonicity and hypotonicity in the pelvic floor and obturator internus

Ask any Women’s Health/Pelvic Health physiotherapist, and most will tell you that they tend to see just as much hypertonicity as hypotonicity of the pelvic floor musculature, and that hypertonicity and tenderness of the obturator internus commonly co-exists with pelvic floor dysfunction.  Is the OI dysfunction a result of, or contributor to, pelvic floor dysfunction? It’s likely that the relationship works both ways, with many potential drivers (see infographic below). It’s our role to work together to unravel the contributors for each person and individualise their care for optimal outcomes.

Table outlining relationships between pelvic floor and obturator internus dysfunction

Considerations for health professionals with a primary role in optimising ‘extra-pelvic’ function

Urinary incontinence can have a significant impact on engagement with physical activity, socialisation, sleep quality, mental distress, and of course overall quality-of-life. This can add substantial burden to that already imposed by hip osteoarthritis or other hip conditions. Those presenting for treatment of hip conditions may not volunteer information on pelvic health, so it’s our role as health professionals to ask those extra questions. Working together with a Pelvic Health Professional may provide far more returns for the individual in your care.

  • Include those extra questions about pelvic health
  • Refer early to a pelvic health professional for assessment if you suspect a pelvic health component – best to know early and work on both concurrently
  • Consider pelvic floor dysfunction as a contributor to persistent buttock or groin pain that does not appear to be responding as expected to an extra-pelvic treatment approach. Refer for an assessment to rule this contributor in or out
  • Consider that exercises for the hip may aggravate pelvic floor hypertonicity or overload a weakened pelvic floor e.g., some abdominal exercises, deep/loaded squats, sumo squats, split lunges, high activation buttock training – banded squats, bridging, monster walks.

Considerations for health professionals with a primary role in optimising intra-pelvic function

While pelvic floor dysfunction may drive hip signs and symptoms, also consider that hip conditions may have a direct impact on pelvic floor dysfunction and may even be the primary driver of dysfunction.

  • Include questions about hip health
  • Refer to an ‘extra-pelvic’ health professional for hip assessment if you suspect a hip component or driver
  • A generic hip exercise program may not be adequate to address hip muscle dysfunction and relieve adverse impact on the pelvic floor e.g., banded clams or squats may worsen rather than help the situation, particularly if there is an issue with hypertonicity in either system
  • Treatments for the pelvic floor may aggravate hip conditions, particularly positions of deep flexion or sustained hip stretches e.g., ‘happy baby’, deep sumo squats, adductor, gluteal or hip flexor stretches. Approaches to management of the hypertonic pelvic floor may need to be modified for those with hip conditions
  • Work with a health professional who has a good knowledge of managing hip conditions to optimise the individual’s management program

It’s critical that we consider the pelvic region holistically and recognise the close relationship between intra-pelvic and extra-pelvic function. While pelvic health management does require specialised training (and we all thank you for your amazing work in this space!), it is important that this subspecialty does not become too far removed. Often there is geographical separation – pelvic health therapists often working in specialised clinics, and professional separation – separate streams in our professional associations and at our conferences, which may broaden the gaps in clinical practice. The hip and pelvic floor are intricately connected. Let’s get it together to optimise care for individuals with hip and pelvic floor dysfunction. 

 

If you are keen to hear more about how we might recognise and co-manage hip and pelvic floor muscle dysfunction, you can access a recording of a recent lecture and discussion within Hip Academy. New members can access recordings of all past meetings.

        HIP ACADEMY MEETING TOPIC:

        The Hip & Pelvic Floor
        Recognising & co-managing dysfunction

A little about our recent live Hip Academy meeting, where we chatted about
The Hip & Pelvic Floor
The lecture included:
    • anatomical & functional relationships between the hip and pelvic floor
    • recognising pelvic floor contributors in those with hip pain
    • recognising hip contributors in those with pelvic floor dysfunction
    • co-managing hip and pelvic floor dysfunction
Followed by member questions and discussion on this topic.
If you are not already a member, you might like to join us for this and future meetings and gain access to recordings of all past meetings, as well as to all online hip courses, ebooks, video library of clinical techniques and a large and growing library of clinical pdf resources.
If you love treating patients with hip pain, or find hip conditions challenging to assess and manage, then Hip Academy is just the place for you!

References

  1. Tuttle LJ, Nguyen OT, Cook MS, Alperin M, Shah SB, Ward SR, Lieber RL. Architectural design of the pelvic floor is consistent with muscle functional subspecialization. Int Urogynecol J. 2014 Feb;25(2):205-12.
  2. Hodges PW, McLean L, Hodder J. Insight into the function of the obturator internus muscle in humans: observations with development and validation of an electromyography recording technique. J Electromyogr Kinesiol. 2014 Aug;24(4):489-96.
  3. Ashton-Miller JA, DeLancey JO. Functional anatomy of the female pelvic floor. Ann N Y Acad Sci. 2007 Apr;1101:266-96.
  4. Amorim AC, Cacciari LP, Passaro AC, Silveira SRB, Amorim CF, Loss JF, Sacco ICN. Effect of combined actions of hip adduction/abduction on the force generation and maintenance of pelvic floor muscles in healthy women. PLoS One. 2017 May 24;12(5):e0177575.
  5. Wang Z, Zhu Y, Han D, Huang Q, Maruyama H, Onoda K. Effect of hip external rotator muscle contraction on pelvic floor muscle function and the piriformis. Int Urogynecol J. 2021 Nov 29. doi: 10.1007/s00192-021-05046-9. Epub ahead of print. PMID: 34842941.
  6. Kruger J, Budgett D, Goodman J, Bø K. Can you train the pelvic floor muscles by contracting other related muscles? Neurourol Urodyn. 2019 Feb;38(2):677-683.
  7. Tuttle, L., DeLozier, E., Harter, K., Johnson, S., Plotts, C. and Swartz, J. The role of the obturator internus muscle in pelvic floor function. Journal of Women's Health Physical Therapy, 2016; 40(1):15-19.
  8. Foster SN, Spitznagle TM, Tuttle LJ, Sutcliffe S, Steger-May K, Lowder JL, Meister MR, Ghetti C, Wang J, Mueller MJ, Harris-Hayes M. Hip and pelvic floor muscle strength in women with and without urgency and frequency-predominant lower urinary tract symptoms. J Womens Health Phys Therap. 2021 Jul-Sep;45(3):126-134.
  9. Hartigan E, McAuley J, Lawrence M et al. Pelvic floor muscle performance, hip mobility, and hip strength in women with and without self-reported stress urinary incontinence. J Womens Health Phys Therap. 2019;43(4):160-170.
  10. Jordre B, Schweinle W. Comparing resisted hip rotation with pelvic floor muscle training in women with stress urinary incontinence. J Womens Health Phys Therap. 2014;38(2):81-89.
  11. Tuttle LJ, Autry T, Kemp C, Lassaga-Bishop M, Mettenleiter M, Shetter H, Zukowski J. Hip exercises improve intravaginal squeeze pressure in older women. Physiother Theory Pract. 2020 Dec;36(12):1340-1347.
  12. Marques SAA, Silveira SRBD, Pássaro AC, Haddad JM, Baracat EC, Ferreira EAG. Effect of pelvic floor and hip muscle strengthening in the treatment of stress urinary incontinence: a randomized clinical trial. J Manipulative Physiol Ther. 2020 Mar-Apr;43(3):247-256.
  13. Tamaki T, Oinuma K, Shiratsuchi H, Akita K, Iida S. Hip dysfunction-related urinary incontinence: a prospective analysis of 189 female patients undergoing total hip arthroplasty. Int J Urol. 2014 Jul;21(7):729-31.
  14. Martines GA, Tamanini JTN, Mota GMDS, Barreto ET, Santos JLF, Sartori MGF, Girão MJBC, Castro RA. Urinary incontinence, overactive bladder, and quality of life in women submitted to total hip replacement. Neurourol Urodyn. 2022 Mar;41(3):830-840.
  15. Baba T, Homma Y, Takazawa N, Kobayashi H, Matsumoto M, Aritomi K, Yuasa T, Kaneko K. Is urinary incontinence the hidden secret complications after total hip arthroplasty? Eur J Orthop Surg Traumatol. 2014 Dec;24(8):1455-60.
  16. Tay K, Tang A, Fary C, Patten S, Steele R, de Steiger R. The effect of surgical approach on early complications of total hip arthroplasty. Arthroplasty. 2019 Sep 3;1(1):5
  17. Okumura K, Yamaguchi K, Tamaki T, Oinuma K, Tomoe H, Akita K. Prospective analyses of female urinary incontinence symptoms following total hip arthroplasty. Int Urogynecol J. 2017 Apr;28(4):561-568.