Snapping Hip (Coxa Saltans)

                                    DR KS Dhillon

Introduction

Snapping hip syndrome is also known as coxa saltans or dancer’s hip. It is a clinical condition characterized by an audible or palpable snapping sensation that is heard during movement of the hip joint. The snapping hip has multiple etiologies and is classified based on the anatomic structure that is causing the snapping sensation. Two main snapping hip categories have been recognized namely:

• Extra-articular

• Intra-articular

There is now increasing knowledge of intra-articular pathologies and the term intra-articular snapping hip has relatively fallen out of favor. These etiologies include labral tears of the hip and loose bodies (e.g. secondary to synovial chondromatosis) [1,2,3].

Extra-articular snapping hip has become subclassified into:

• External snapping hip

• Internal snapping hip

External snapping hip is usually attributed to the iliotibial band moving over the greater trochanter of the femur during hip movements. Other causes include: 

• The proximal hamstring tendon rolling over the ischial tuberosity.

• The fascia lata or the anterior aspect of the gluteus maximus rolling over the greater trochanter.

• The psoas tendon rolling over the medial fibers of the iliacus muscle. 

A combination of defects is also possible. Thickening of both the posterior iliotibial band and anterior gluteus maximus can snap over the greater trochanter at the same time [4,5].

Internal snapping hip is usually caused by the iliopsoas tendon snapping over underlying bony prominences, such as the iliopectinal eminence or the anterior aspect of the femoral head. Other causes include partial or complete bifurcation of the iliopsoas tendon and paralabral cysts. The snapping sensation can closely mimic intra-articular pathology. Proper physical exams and imaging can differentiate the two. In approximately 50% of internal snapping hip cases, an additional intra-articular hip pathology is present.

Etiology

Snapping hip is most often an overuse phenomenon. It may be precipitated by trauma due to intramuscular injection into the gluteus maximus and surgical procedures. Coxa vara following total hip arthroplasty has been linked to the development of external snapping hip syndrome. There are other anatomical variations that may predispose to coxa saltans. These include an increased distance between the greater trochanters, prominent greater trochanters, and narrow bi-iliac width. Iliotibial band tightness, muscle tightness, shorter muscle or tendon lengths, or inadequate relaxation of the muscles may contribute to the development of snapping hip. Sometimes no etiology can be found resulting in an idiopathic classification [6].

Epidemiology

Approximately 5% to 10% of the population is affected by coxa saltans. The majority of patients experience painless snapping. The prevalence is slightly higher in women than in men. The individuals typically affected include those who do repetitive extreme hip motions. These include competitive and recreational ballet dancers, soccer players, weight lifters, and runners. Ninety percent of the competitive ballet dancers have reported symptoms of snapping hip syndrome and 80% have bilateral involvement. Movements that provoke snapping include external hip rotation and abduction at or over 90 degrees.

Pathophysiology

The external snapping hip syndrome is usually caused by the iliotibial band snapping over the greater trochanter of the femur during movements such as flexion, extension, and internal or external rotation.

Internal snapping hip is usually caused by the iliopsoas tendon snapping over underlying bony prominences, such as the iliopectinal eminence or the anterior aspect of the femoral head.

History and Physical

A good history and physical examination often can help pinpoint the correct anatomic region of the snapping. The patient usually can point with a finger to the area that is painful upon snapping and may even be able to recreate the snap. Symptoms develop and increase over a long period, typically months to years. 

External snapping hip is usually obvious on clinical examination. The patient experiences snapping or a sensation of subluxation of the hip. Sometimes the patient can even palpate the snapping phenomenon under the skin. The area over the greater trochanteric region can be painful due to abductor tendon pathology, greater trochanter bursitis, or inflammation of the iliotibial band. Tests to provoke the snap usually include femoral flexion or rotation. During the examination of the hip, the patient is placed in a lateral position, and the Ober test is done to test for iliotibial band tightness. With the patient in the same position, the knee and hip can be cycled through flexion and extension to provoke the snapping.

In patients with internal snapping hip, there is snapping or locking of the hip with an audible snap. Gluteus medius weakness is sometimes found. For examination of the hip, the patient is placed in the supine position with the affected hip guided by the examiner into an externally rotated and flexed position. From this position, the leg is extended into a neutral position next to the other resting leg. This test is positive if the snapping is reproduced at the anterior part of the hip.  

Evaluation

In the event that history and physical examination fails to diagnose coxa saltans, imaging can be used to help rule out other hip pathology and confirm the diagnosis. Plain radiographs are usually of not much value to confirm the diagnosis. They, however, are done to rule out anatomical variations, developmental dysplasia, or other hip pathology. A positive response to anesthetic injection into the joint in the affected area can help distinguish between external and internal snapping hip syndrome [3,6,7,8,9].

External snapping hip syndrome can be confirmed on T1 weighted axial MRI as a thickened iliotibial band or thickened anterior edge of the gluteus maximus muscle. If the snapping is not felt on physical examination, dynamic ultrasonography can be used to demonstrate the snapping of the iliotibial band over the greater trochanter. Dynamic ultrasonography can also reveal associated iliopsoas bursitis, tendonitis, and muscle tears. 

The diagnosis of internal snapping hip syndrome can be confirmed using iliopsoas bursography combined with fluoroscopy, magnetic resonance imaging, dynamic ultrasonography, or magnetic resonance arthrography. Magnetic resonance arthrography is preferred because it can also detect intra-articular hip pathology, which often accompanies internal snapping hip syndrome.

Management

When there is no pain treatment is not needed. When there is pain with snapping, treatment is conservative. It consists of rest, physical therapy, stretching, steroid injections, oral anti-inflammatory medications, and activity modification. In most patients, these measures are effective in relieving the pain.

Surgery may be warranted if the pain persists despite these conservative measures. For external snapping hip syndrome, iliotibial band loosening is usually the goal. This can be accomplished with either open or arthroscopic procedures. The iliotibial tendon can be lengthened or completely released using various procedures such as Z-lengthening, a cross-shaped release, a Z-shaped release, or a gluteus maximus release. If the release is excessive or there is damage to the surrounding area, weakness in abduction may be a complication [10].

For the internal snapping hip syndrome open or arthroscopic procedures are also available to lengthen or release the iliopsoas tendon. Usually,

arthroscopic methods are preferred to avoid complications of open surgery. The most common side effect of iliopsoas release is hip flexor weakness. This can occur if there is excessive release or there is damage to the surrounding area. 

Surgeries for external and internal snapping hip can result in other complications such as infection, muscle atrophy, heterotopic ossification, continued symptoms, or nerve damage.

Differential Diagnosis

The differential diagnosis of snapping hip includes:

• Acetabular Labral Tear

• Femoral Head Avascular Necrosis

• Hip Tendonitis

• Iliopsoas Tendinitis

• Bursitis; Greater Trochanteric or Iliopsoas

• Iliotibial Band Syndrome

• Intra-Articular Loose Body of the Hip

• Synovitis

Conclusion

Snapping hip syndrome is a primarily asymptomatic hip disorder that is characterized by a snapping sound or sensation upon specific hip movements. It has several etiologies that are classified based on the anatomical structure causing the snapping sensation. Extra-articular snapping hip syndrome (SHS) comprises two main classes i.e. external SHS, involving the iliotibial tendon, and internal SHS, involving the iliopsoas tendon. It is important to distinguish intra-articular pathologies from extra-articular SHS. Intra-articular processes are more acute, trauma-related, and largely more painful and debilitating.

Internal (iliopsoas) snapping is typically audible, while external (iliotibial) snapping is usually palpable. The etiologies are multifactorial. Both present with a broad spectrum of symptoms, including pain and decreased mobility. The true prevalence, however, remains unknown. It is estimated that about  5-10% of the population has some degree of SHS. Specific populations such as avid runners, ballet dancers, and gymnasts are more prone to develop this condition due to overuse and hypertrophy of involved anatomy. The most sensitive diagnostic tool is reproducing the snap with physical examination and movement. X-rays, MRI, dynamic ultrasound, and CT scans can supplement the diagnosis and confirm the underlying cause. Symptomatic patients are usually managed with NSAIDs, rest, physical therapy, and corticosteroid injections or analgesics. If pain and snapping persist, endoscopic disengagement of the iliopsoas or iliotibial tendon is carried out.

References

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2. May O. Arthroscopic techniques for treating ilio-psoas tendinopathy after hip arthroplasty. Orthop Traumatol Surg Res. 2019 Feb;105(1S):S177-S185. 

3. Nolton EC, Ambegaonkar JP. Recognizing and Managing Snapping Hip Syndrome in Dancers. Med Probl Perform Art. 2018 Dec;33(4):286-291. 

4. Snapping Hip Syndrome. Orthop Nurs. 2018 Nov/Dec;37(6):361-362. 

5. Badowski E. Snapping Hip Syndrome. Orthop Nurs. 2018 Nov/Dec;37(6):357-360.

6. Flato R, Passanante GJ, Skalski MR, Patel DB, White EA, Matcuk GR. The iliotibial tract: imaging, anatomy, injuries, and other pathology. Skeletal Radiol. 2017 May;46(5):605-622.

7. Macke C, Krettek C, Brand S. [Tendinopathies of the hip : Treatment recommendations according to evidence-based medicine]. Unfallchirurg. 2017 Mar;120(3):192-198. 

8. Chang CY, Kreher J, Torriani M. Dynamic sonography of snapping hip due to gluteus maximus subluxation over greater trochanter. Skeletal Radiol. 2016 Mar;45(3):409-12. 

9. Potalivo G, Bugiantella W. Snapping hip syndrome: systematic review of surgical treatment. Hip Int. 2017 Mar 31;27(2):111-121. 

10. Ilizaliturri VM, Camacho-Galindo J. Endoscopic treatment of snapping hips, iliotibial band, and iliopsoas tendon. Sports Med Arthrosc Rev. 2010 Jun;18(2):120-7.