Soft-Tissue Sources of Extra-articular Pain Following Total Hip Arthroplasty: A Comprehensive Review

Abstract

Hip pain after a total hip arthroplasty is a prevalent condition. Once aseptic loosening and infection have been ruled out, the possible entities are vast. Accurate diagnosis in this patient population is challenging because they might present in different stages of their recovery process and the potential overlap of some conditions. Given the high expectations clinicians and patients have from hip arthroplasty, a multifaceted patient-specific approach is crucial to clinical decision making. Advances have been made to better stratify patients into the spectrum of management, which includes nonsurgical treatment, injections, such as orthobiologics, arthroscopic hip surgery, open surgery, and, in rare cases, revision total hip arthroplasty.

Total hip arthroplasty (THA) stands as a one of the most successful surgeries in orthopaedic care, offering unparalleled relief to patients suffering from hip osteoarthritis by restoring function and improving the quality of life. Over the years, advancements in surgical techniques and implant designs have continually refined the outcomes of this procedure.¹

Nevertheless, persistent pain after THA is a common condition with a reported prevalence ranging from 0.4% to 18.3%.² The possible causes are vast, and after ruling out deep joint infection and aseptic loosening, an adequate diagnostic algorithm is key as multiple etiologies can be present.

Extra-articular causes of persistent hip pain after THA can present with differing areas of pain. Iliopsoas tendonitis is a common but underrecognized cause of anterior discomfort. Pain experienced over the lateral aspect of the hip is commonly referred to as greater trochanteric pain syndrome, which encompasses a wide spectrum of pain sources, including trochanteric bursitis and abductor to gluteus medius (GM) tendon tears. Alternatively, pain in the posterior hip or buttock may be referred from disease in the lumbar spine or, less frequently, from deep gluteal space (DGS) pathology, such as piriformis syndrome (PS) or proximal hamstring pathology. Addressing these pathologies promptly has been established to have a notable effect on the outcomes for this population.

The purpose of the present review is to detail the history, physical examination, and diagnostic workup of extra-articular sources of pain after THA. It will also present evidence of surgical outcomes and tools to assist with treatment decision making in this population (Table 1).

Table 1.

Differential Diagnosis of Extra-articular Hip Pain After Total Hip Arthroplasty

Location of Pain	Conditions	Risk Factors
Anterior hip pain	Iliopsoas impingement/tendinitis	Cup overhang >4 mm
		Prominent screws
		Younger age
		Flexion activities overuse
		Collared stem
		Spine stiffness
		LLD >10 mm
		Excessive femoral retroversion
Lateral hip pain	Greater trochanteric syndrome	Female sex
	Trochanteric bursitis	Diabetes mellitus
	Gluteus medius tendinosis/tear	Hypertension
		Acetabular offset liners
		Increased global offset
		LLD >5 mm
		Older age
Posterior hip pain	Deep gluteal syndrome	aUnrepaired trochanteric bursa
	Piriformis syndrome	Smoking
	Hamstring tears	Previous hamstring tear
		Older age

LLD = length leg discrepancy

^aPosterior approach.

Anterior Hip Pain

Iliopsoas Impingement/Tendinitis

The iliopsoas muscle and tendon are formed by the convergence of the psoas and iliacus muscles. The psoas muscle originates from the lumbar vertebrae and joins the iliacus muscle at the L5 to S2 levels to form the iliopsoas muscle. The iliopsoas tendon originates at the level of the inguinal ligament and courses distally, running immediately anterior to the hip joint. It has a close anatomical relationship with the anterior hip capsule and inserts on the lesser trochanter of the femur. Cadaveric and radiographic studies have shown different anatomical variants, with single, double, or triple tendon bundles.³ The muscle is the major hip flexor and aids with hip external rotation.

Clinical Presentation

Patients typically present with anterior hip pain or in the groin area, especially with activities requiring hip flexion.³ However, the clinical spectrum ranges for subtle persistent groin pain that is exacerbated by standing from a sitting position, climbing upstairs, or activities that involved hip flexion.

Patients with iliopsoas impingement may experience an audible snap when bringing the hip into flexion and external rotation followed by extension. This phenomenon called internal snapping often presents asymptomatically. However, repetitive snapping and possible involvement of the iliopsoas bursa can lead to inflammation and pain.

Although there are not specific clinical tests to identify iliopsoas tendinitis, pain can be reproduced or exacerbated by resisted hip flexion, straight leg raise test, and deep palpation of the tendon.

Diagnostic Studies

Iliopsoas tendonitis may develop secondary to impingement with the acetabular cup during hip flexion and hip flexion activities overuse. Efforts have been made to identify potential risk factors for this condition. Some authors have suggested younger age, spinal fusion, acetabular overhanging more than 8 to 10 mm, large acetabular implant, prominent acetabular screws through the ilium, excessive femoral retroversion, collared stems, leg length discrepancies over 10 mm, and increased overall offset as potential risk factors.^2,4,5

Initial radiographic evaluation should include plain radiographs with anterior-posterior and cross-table lateral views to identify some of the previously reported potential risk factors for this condition. Some authors have suggested several factors, including an acetabular overhang of more than 8 mm on a cross table lateral radiograph, a larger acetabular implant, prominent acetabular screws through the ilium, excessive femoral retroversion, collared stems, leg length discrepancies over 10 mm, and increased overall offset as potential risk factors.

CT scans are useful to further evaluate the mentioned risk factors and the overall position of the acetabular cup in space. Some authors have supported the utility of a CT scan to evaluate patients with iliopsoas tendonitis. For instance, Baujard et al⁶ recently presented an analysis based on the CT scans of 130 patients after primary THA who presented with iliopsoas tendonitis due impingement symptoms; patients were propensity matched to a control group of patients without complains of iliopsoas tendonitis. The authors found that an overhang acetabular cup ≥4 mm positively correlated with impingement. Below this threshold, different sources of impingement or anterior hip pain should be ruled out. Furthermore, Carbonell-Rosell et al⁷ reported that patients with cup malposition and an overhang of ≥8 mm might benefit from an acetabular implant revision, whereas patients below that threshold are better candidates for endoscopic procedures.

Although metal suppression MRI is less commonly used in the evaluation of iliopsoas impingement, new MRI techniques with improved resolution and metal artefact reduction sequence are useful to detect fluid collection, hypertrophic bursitis, iliopsoas tendonitis, and increased signal intensity in the periprosthetic soft tissues.

Finally, the use of dynamic studies for diagnosis confirmation purposes is critical. Guided diagnostic and therapeutic peritendon injections have been reported to be a trustful tool. A positive response, defined as a notable pain relief of groin pain following a targeted injection, strongly suggests that the iliopsoas tendon is the source of the pain and confirms the diagnosis.⁸

Treatment

The first line of treatment is commonly conservative, including physical therapy, nonsteroidal anti-inflammatory drugs (NSAIDs), activity modifications, rest, and peritendinous steroid injections, with high are rate of successful reported. For instance, Weintraub et al recently presented a case series, including 42 patients with iliopsoas tendonitis who underwent iliopsoas peritendon ultrasound-guided injections with a resolution of groin pain in 78.6% of patients in the cohort. It is important to note that patients with higher acetabular overhang had lower successful rates.⁹

However, in recalcitrant cases, surgical intervention may become necessary. Surgical options include iliopsoas tendon release, iliopsoas fractional lengthening, removal of protruding screws, and acetabular revision alone or in combination with iliopsoas tendon release.^10,11

Currently, open and endoscopic techniques have been described to address the iliopsoas tendon. O'Sullivan et al¹² were among the first to report favorable outcomes after open iliopsoas tenotomy in a case series of 16 patients after THA, with only one patient requiring further intervention due to acetabular malposition. More recently, endoscopic tenotomy has emerged as a successful less invasive approach for treating iliopsoas tendonitis. Dora et al¹³ reported that iliopsoas tenotomy provided the same functional results as acetabular revision without the added risks associated with an acetabular cup revision.

However, concerns have been raised about the potential loss of hip flexion strength and range of motion associated with tenotomy. Finsterwald et al¹¹ reported on 36 patients who underwent endoscopic iliopsoas tenotomy. Notable improvements were observed in the evaluated patient-reported outcomes at six months, one-year, and two-year follow-up points. However, the authors reported a decrease in active hip flexion and isometric hip flexion strength of 12% and 20%, respectively.

Iliopsoas fractional lengthening (IFL) has been widely used in the hip preservation world; proponents of this technique suggest that by addressing the iliopsoas and the muscular-tendon interface, hip strength and range of motion are preserved.^14,15 In line with this, Simon et al¹⁰ recently reported on 60 hips that underwent endoscopic IFL with a minimum one-year follow-up. Favorable outcomes were reported with an overall mean satisfaction of 7.2 and a mean mHHS of 73.9 at the latest follow-up. Furthermore, 77% of patients reported feeling much or slightly better and 60% reported subjective hip strength improvement (Figure 1).

Figure 1.

A, Cross-table lateral radiograph showing acetabular cup overhang. B, Endoscopic identification of the iliopsoas tendon. C, Iliopsoas fractional lengthening at the tendon-muscle junction.

Revision acetabular cup should be reserved for cases where an overhand of 8 mm or greater is found. In such situations, the use of a lower-profile acetabular cup with medialization, when feasible, is recommended to prevent further impingement while maintaining appropriate version and inclination. Multiple techniques have been described, including downsizing the acetabular cup with the addition of bone graft to address any potential bony defects, using multiple screw fixation, reinforced rings, or even custom implants, depending on the surgeon's expertise and preference.^16-18 Chalmers et al¹⁹ reported 92% of resolution of symptoms after acetabular revision in patients with at least 8 mm anterior prominence. Similarly, Batallier et al reported on 46 patients who underwent cup revision due to iliopsoas impingement. The mean cup prominence was 9.9 mm, with 76% of patients showing radiographic evidence of cup malposition. Cup fixation was achieved using a press-fit cup in 87% of cases, whereas 8.7% required a cemented cup and 4.3% required a reinforcement ring. Notably, 85% of patients were satisfied with their outcomes, with a mean follow-up of 21 months.¹⁸

Lateral Hip Pain

Greater Trochanteric Pain Syndrome

Pain experienced over the lateral aspect of the hip is commonly referred to as greater trochanteric (GT) pain syndrome. This condition encompasses greater trochanteric bursitis, GM, and gluteus minimums tears.²⁰

Trochanteric Bursitis

Trochanteric bursitis (TB), or inflammation of one or more of the peri-trochanteric bursae, has historically been considered a primary source of lateral hip pain, with an approximate prevalence of 4.4% to 29% in patients post-THA.²¹ A proposed cause is repetitive friction between the GT and the iliotibial band, commonly associated with overuse, trauma, and altered gait patterns. Teng et al²² investigated the effect of performing a bursectomy during primary THA. In this study, 550 patients underwent routine bursectomy, while 400 did not. At an 11-year follow-up, the incidence of tb was unaffected by whether a bursectomy was performed. Furthermore, White et al recently conducted a risk factor analysis for the development of trochanteric bursitis TB, evaluating 1094 patients, of whom 103 (9.4%) developed TB. The incidence varied slightly by surgical approach: 8.7% for the posterior approach, 10.8% for the direct anterior approach, and 4.2% for the direct lateral approach. However, the surgical approach was not identified as a notable risk factor. Among the variables analyzed, only sex was markedly associated with increased risk; women had a 1.79 times higher risk of developing TB. Notably, changes in acetabular offset, femoral offset, total offset, and leg length between preoperative and postoperative radiographs were not associated with an increased risk of TB in either univariate or multivariate model.²³

Clinical Presentation

Patients usually complain of lateral thigh pain, often aggravated by prolonged sitting or stair climbing, with a tender area on the GT to palpation.

Diagnostic Studies

Although in most cases, diagnosis is made clinically, advance imaging, metal suppression MRI, or ultrasound (US) can be used to rule out concomitant abductor pathology.

Treatment

Trochanteric bursitis initially is managed conservatively with simple analgesia, NSAIDs, physiotherapy, and corticosteroid injections. For refractory cases where conservative measures have failed for a prolonged period, open techniques combining iliotibial band release with trochanteric bursectomy, an arthroscopic approach to debride and excise the inflamed bursa, are recommended. Van Hofwegen et al²⁴ presented a series including 12 patients who underwent endoscopic trochanteric bursectomy with a high patient satisfaction, where 10 out the 12 patients reported substantial pain relief.

Gluteus Medius Tendinitis and Tears

This pathology has been observed in a substantial proportion of patients with osteoarthritis undergoing THA, affecting approximately 20% to 25% of this patient population; in addition, approximately 11% of patients post-THA experience lateral hip pain related to GM pathology.²⁵ Previous studies have identified female sex, diabetes mellitus, hypertension, the use of offset acetabular liners, an increased global offset, and a length leg discrepancy ≥5 mm as independent risk factors.²⁶ Furthermore, the surgical approach used during THA may also influence postoperative muscle integrity. Agten et al investigated muscle alterations following primary THA by comparing different approaches. The study included 120 patients, with 30 undergoing postoperative MRI for muscle assessment. The findings demonstrated that anterolateral and anterior approaches were associated with less soft-tissue damage. By contrast, the posterior approach showed notable damage to the external rotator muscles, whereas the direct lateral approach resulted in notable injury to the gluteal musculature.²⁷ Similarly, Svarnas et al²⁸ conducted an MRI-based study comparing muscle changes across various surgical approaches. Their results indicated that anterior-based approaches were associated with less damage to the GM. However, both anterior and posterior approaches showed degeneration of the gluteus minimus, whereas the direct lateral approach caused the most substantial damage to the GM.

It has also been established that patients undergoing primary THA or those presenting with postoperative GM pathology tend to experience inferior patient reported outcomes.²⁹

Clinical Presentation

Clinical presentation is similar to the one observed in trochanteric bursitis. Previous studies indicate that the resisted internal rotation test has a sensitivity of 92% and a specificity of 85%. The resisted abduction test demonstrates a sensitivity of 73% and a specificity of 87%. By contrast, the Trendelenburg gait test shows a lower sensitivity of 33% but a specificity of 100%. In addition, tenderness at the GT has a sensitivity of 88% and a specificity of 75% for detecting GM tears.³⁰

Diagnostic Studies

The use of diagnostic imaging techniques, such as metal suppression MRI and ultrasound, as both diagnostic and therapeutic tools has improved the recognition of hip abductor pathologies as underlying causes of hip pain. GM pathologies are typically classified as tendinosis, partial thickness tears (low grade if less than 50% of the tendon is involved, high grade if more than 50% is involved), or full-thickness tears.

Plain radiographs are part of the initial evaluation. Previous studies have shown that the presence of trochanteric enthesophytes protruding more than 2 mm from the cortical surface has a positive predictive value of 90% for gluteal tendon degeneration and peritendinous edema on MRI.³¹

Ultrasound is useful for evaluating GM tendon pathology, offering a noninvasive, cost-effective, and dynamic assessment method. This modality provides real-time visualization of soft tissue, enabling detailed examination of tendon structure, vascularity, and associated musculature, although it is limited by its dependence on the skill of the user.

MRI is commonly used to diagnose GM pathologies. The identification of an area of T2 hyperintensity superior to the greater trochanter has the highest sensitivity (73%) and specificity (95%) for tears. A partial thickness tear is diagnosed when the tendon is thickened with increased signal intensity on T2-weighted images. Focal discontinuity of the tendon with any degree of retraction indicates a complete tear³² (Figure 2).

Figure 2.

A, Anterior-posterior radiograph of right hip showing enthesophytes at the GM insertion. B, Sagittal view of right hip T2-weighted MRI image showing notable tendonitis and a partial GM tear. C, Coronal view of left hip T2-weighted MRI image showing a massive retracted tear.

Treatment

Nonsurgical should be considered as the initial approach, including physical therapy focusing on GM strength and stretching. A recent study demonstrated better muscle activation and strength compared with regular conventional therapy.³³ NSAIDs and guided cortisone or biological injections have also been proposed as effective nonsurgical treatment. For instance, Lee et al presented a study involving 21 patients diagnosed with chronic GM tendinosis and/or partial tears in native hips who did not respond to traditional physical therapy and NSAIDs. These patients received an injection of platelet-rich plasma (PRP), resulting in favorable outcomes with notable improvements in functional outcomes.³⁴ Although the efficacy of this intervention following hip arthroplasty has not been established, recent reports have demonstrated the safety of PRP injections in patients with hip prostheses.³⁵

Surgical treatment is reserved for recalcitrant cases, where repair, reconstruction, or tendon transfer are valuable options.^29,36,37 Open and endoscopic repair techniques demonstrate similar functional outcomes with low complication rates.³⁸

Multiple endoscopic repair techniques have been described based on the degree of the tendon tear. For cases of GM tendinosis, trochanteric micropuncture has been proposed as a potential treatment to enhance healing through bone marrow stimulation, although there is a lack of evidence on the outcomes of this technique. For partial thickness low-grade tears, where the tendon is unstable on the lateral facet of the GT, the suture staple technique has shown favorable outcomes. In this procedure, a microfracture awl is used to create multiple holes in the lateral facet through the partially torn GM, and the repair is done in a transtendinous fashion³⁹ (Figure 3).

Figure 3.

Illustration showing surgical treatment for partial gluteus medius tendon tear. A, Transtendinous technique, two anchors are placed in a transtendinous fashion. B, Final repair configuration of the transtendinous technique. C, Suture staple technique, four anchors are placed in the greater trochanter throughout the GM tendon. D, Final repair configuration of the suture staple technique. GM = gluteus medius

For higher-grade partial thickness tears, a transtendinous technique is used. A longitudinal incision is made in line with the tendon fibers. Torn fibers on the deep side of the tendon are debrided, followed by decortication of the tendon footprint. Two or three anchors are placed in the prepared area, with the sutures passed through the tendon in a mattress configuration.⁴⁰ Furthermore, for full-thickness tears, a double row mattress repair is recommended, where the sutures are crossed to allow for greater distribution of force and compression across the tendon.⁴¹

Maldonado et al presented a case series involving 30 patients who underwent GM repairs using one of the described techniques in patients with hip arthroplasty. At a mean follow-up of 24.2 ± 19.3 months, notable improvements in functional outcomes and high patient satisfaction were reported.⁴²

In rarer cases involving extensive fat tissue degeneration or massive tendon retraction, certain salvage techniques have been proposed. For instance, in cases of massive and retracted tears, a dermal allograft can be used as an augmentation to add biomechanical strength and reinforce the repair. A total of three anchors are placed over the lateral facet of the GT to form the proximal row of the construct. The sutures are then passed through both the tendon and the allograft in a mattress configuration, and the graft is secured down to the trochanter.⁴³ In addition, a gluteus maximus transfer has been proposed as a salvage procedure to address irreparable GM tears. In this technique, a longitudinal incision is made directly over the posterior third of the GT. The posterior third of tensor fascia lata and the anterior third of the gluteus maximus are then incised to create a triangular flap, which is mobilized and attached to the GM footprint to restore function. Maldonado et al reported on 18 patients who underwent this procedure, observing notable improvements in functional outcomes. However, abductor strength improved in 41% of patients, although it remained unchanged in the remaining 59%⁴⁴ (Figure 4).

Figure 4.

Flow chart showing gluteus medius pathology treatment algorithm.

Posterior Hip Pain

Deep Gluteal Space Syndrome

The DGS is an anatomic area in the posterior hip and pelvic region bordered by the gluteus maximus posteriorly; the posterior ilium, ischium, posterior acetabulum, and the femoral head and neck anteriorly; and the greater trochanter laterally. A recent publication by Fırat et al⁴⁵ found that patients undergoing posterior approach with the trochanteric bursa left unrepaired and increased the odds of patients reporting DGS pain syndrome.

Piriformis Syndrome

PS occurs when the piriformis muscle compresses or irritates the sciatic nerve, causing symptoms such as buttock and leg pain, altered sensations along the nerve's path, and discomfort while sitting. This condition is more commonly discussed in hip preservation literature, with a few reports in patients post-THA.

Clinical Presentation

Patients often present with vague symptoms that considerably overlap with those of other hip, pelvic, and lumbar spine pathologies, making precise clinical assessment challenging. Multiple clinical tests have been described: the straight leg raise test has a sensitivity of 15% and a specificity of 95%, the active piriformis test shows a sensitivity of 78% and specificity of 80%, and the seated piriformis stretch test has a sensitivity of 52% and specificity of 90%. Furthermore, combining the active piriformis test with the seated piriformis stretch test yields a reported sensitivity of 91% and specificity of 80%.⁴⁶

Diagnosis Studies

A lumbar MRI examination should be considered to rule out underlying back pathology. Improved MRI resolution, the use of ultrasound-guided injections, and increased awareness may enhance the accuracy of diagnosing PS. However, in our experience, no single diagnostic tool is reliably accurate when used in isolation. The diagnosis is most accurately confirmed when guided injections are used in cases with a high degree of clinical suspicion.

Treatment

Initial management of PS involves rest, activities modifications, NSAIDs, and guided steroids injections, which typically yield positive responses in most cases.

For recalcitrant cases, surgical interventions, such as sciatic neurolysis and piriformis tenotomy, have been the mainstays of treatment, with both open and endoscopic techniques showing favorable outcomes. For instance, Uchio et al presented a case report of a patient with bilateral PS, 4 and 6 years after a cementless THA. After failing conservative treatment, the patient underwent open tenotomy and sciatic neurolysis, resulting in complete resolution of symptoms.⁴⁷ The modern endoscopic release of the piriformis tendon and exploration of the sciatic nerve is currently the standard of treatment for these unresponsive cases⁴⁸ (Figure 5).

Figure 5.

Images showing endoscopic sciatic neurolysis and piriformis tendon release. A, Adhesions and fibrotic bands in the deep gluteal space. B, Identification of entrapment site. C, Post piriformis tendon tenotomy. Arrows: 1: Piriformis muscle. 2: Sciatic nerve.

Proximal Hamstring Tears

The proximal hamstrings originate from the ischial tuberosity and include the semimembranosus, semitendinosus, and the long head of the biceps femoris. The latter two muscles arise from a shared conjoined tendon. Proximal hamstring injuries can occur across all ages and levels of physical activity. The most notable risk factors include older age and the history of hamstring injury. These injuries can range from mild strains to more severe partial or full-thickness tears. They occur at the musculotendinous junction, as avulsions from the insertion site on the ischial tuberosity, or as midsubstance tears. They often result from sudden, forceful, eccentric contractions, especially during the late swing phase of movement. At this point, the hamstrings are under maximum strain when the hip is flexed, and the ipsilateral knee is extended. Although the literature on hamstring injuries in the native hip is extensive, this condition following THA is rare, with existing reports limited to isolated case studies.⁴⁹

Clinical Presentation

Patients often describe the injury as a sharp, acute pain in the back of the thigh, immediately followed by difficulty walking. The resulting stiff-legged gait stems from their attempt to avoid flexing both the hip and knee. Typically, patients present with pain in the posterior thigh, especially below the ischial tuberosity, where the tendon has retracted. This is often accompanied by notable ecchymosis, resulting from the hematoma caused by the tendon rupture. In addition, patients frequently report discomfort when sitting due to pain localized at the avulsion or tear site. In cases of complete tears with tendon retraction, a visible deformity may also be observed.⁵⁰

Diagnosis Studies

Plain radiographic films are useful as the initial diagnostic tool to rule out ischial tuberosity avulsion fractures. However, MRI is considered the gold standard for diagnosing hamstring injuries, offering detailed insights into the extent and location of the injury, tendon involvement, and chronicity of the lesion. Metal suppression MRI is particularly useful in differentiating between partial and complete tears.

Treatment

Nonsurgical treatment for hamstring injuries typically includes rest, physical therapy, extracorporeal shock-wave therapy, and biological injections, such as PRP, have shown good results, especially in subacute or chronic cases without notable tendon retraction.⁵¹ Conversely, surgical treatment is generally reserved for more severe cases, such as complete tendon avulsions involving two or three tendons or injuries that did not respond to conservative methods. Open surgery is frequently used for acute or chronic injuries with notable retraction, whereas endoscopic techniques are more suitable for partial tears. Postsurgical outcomes are generally positive, with high rates of patient satisfaction. However, the efficacy of these techniques post THA is limited.⁵²