The differential diagnosis for hip pain includes the lumbar spine, pelvic girdle, and intra- and extra-articular sources around the hip joint. The distribution of pain from these sources commonly overlaps and contributes to diagnostic dilemmas. Further, the interrelationship of force transmission and movement across the hip, pelvic girdle, and spine results in the possibility of coexisting disorders (1). Intra-articular hip pain can be a critical source of pain, impairment, and loss of function in patients with isolated and coexisting disorders. Establishing a specific diagnosis is essential because diagnosis directs and determines treatment. In turn, specificity of treatment can improve outcomes.

This chapter will discuss sources of pain to consider in patients presenting with posterior pelvis, lateral hip, groin, and thigh pain. Further, we will discuss the possible options that can be used to diagnosis hip disorders.

One of the main difficulties with hip, pelvic girdle, and spine pain is the similarity in their clinical presentations. Descriptive studies have reported pain distributions that overlap between the spine, pelvic girdle, and hip. LBP with radiculopathy, facet-mediated pain, and the sacroiliac joint (SIJ) pain have been found to present with similar distributions of pain across the posterior pelvis with radiation, in some cases, into the lateral hip and/or groin. Extra-articular hip pain such as piriformis syndrome and greater trochanteric bursitis and pain syndrome can also present with similar distributions of pain including the posterior pelvis, lateral hip, and thigh (2,3,4).

One reason for the significant overlap in pain diagrams related to hip, pelvic girdle, and lumbar disorders is the overlap in innervation. Innervation of the lumbar facet joints in the spine is from the medial branches of the dorsal rami of L1 through L5 (5). Intervertebral discs are innervated by multiple nerves including the sinuvertebral nerves, adjacent ventral primary rami, and grey rami communicans (6). The SIJ is innervated by dorsal rami of L2–S2 nerve roots with primary S1 innervation to posterior fibers of the dorsal SIJ ligament (7). Further, the mechanoreceptors of the SIJ provide proprioception information and potentially pain. These mechanoreceptors likely provide information to and provide position sense and balance to the trunk (8). The hip also has a wide distribution of innervations. The anterior joint capsule is innervated by the obturator nerve and femoral nerve (L2–L4), and the posterior capsule is innervated by the sciatic nerve and superior gluteal nerve (L4–S1) (9).

Historically, the distribution of pain attributed to an intra-articular hip joint disorder has been primarily restricted to the groin and anterior thigh (10). However, there is evidence that the distribution of intra-articular hip pain can include the lower extremity. In a study of patients with osteoarthritis (OA) scheduled to undergo primary hip arthroplasty or revision, 73% reported groin pain and 27% reported pain referral to the knee (11). Lesher et al. (12) described pain diagrams of patients reporting 90% relief in pain following a fluoroscopically guided intra-articular hip injection for painful degenerative hip disorders. Twelve different patterns of pain distributions were described and included: 20% posterior pelvis and thigh; 18% posterior pelvis and groin; 12% posterior pelvis alone; 12% to the groin alone; 6% thigh (grouping anterior, posterior, and lateral together); 6% posterior pelvis, groin, and thigh; and 2% to the thigh and leg. Accounting for an additional 16%, six patterns involved the posterior pelvis combined with groin, thigh, leg, or foot. Other studies have described prearthritic hip disorders to present with pain beyond the groin and anterior thigh. Byrd (13) described patients with painful hip acetabular labral tears presenting with a “C” sign; a patient’s indication of pain noted when the patient places his/her index finger over the anterior aspect of the hip and the thumb over the posterior trochanteric region. Another study (14) describing painful acetabular hip labral tears reported 92% of the patients had groin pain, 59% had lateral hip pain, 52% had anterior thigh/knee pain, and 38% had buttock pain. For patients presenting with femoroacetabular impingement (FAI) requiring surgical intervention, Clohisy et al. (15) reported 88% of
patients had groin pain, 67% had lateral hip pain, 35% had anterior thigh pain, 29% had buttocks pain, 27% had knee pain, and 23% had low back pain. Further, patients treated surgically for symptomatic developmental hip dysplasia (DDH) (16) presented with similar distributions of pain. Sixty-six percent had groin pain, 64% lateral hip pain, 28% anterior thigh and knee pain, and 17% posterior pelvic pain. These studies challenge the traditional concept that intra-articular hip pain presents with groin pain in isolation and instead puts forward the hip can refer pain into the lateral hip, posterior pelvis (buttocks), low back, and lower extremity. Further, pain distributions do not distinguish one type of intra-articular hip disorder from another.

Pain distributions related to intervertebral disc disorders have been determined by lumbar provocation discography. Intradiscal infusion of contrast in symptomatic patients recreated pain in the groin, buttocks, hip, and lower extremities (17). Noxious stimulation of the interspinous ligament and paravertebral muscles has also been described to refer pain into the posterior pelvis and lower extremity (18,19). Pain related to the facet joints was first described by Mooney and Robertson (20). They performed provocative intra-articular facet injections and determined the facets refer pain in a similar distribution as other lumbar and pelvic girdle disorders including the low back, posterior pelvis, and lateral hip. A subsequent study by Marks (21) found no consistent segmental or sclerotomal pattern for facet-mediated pain in patients undergoing diagnostic medial branch blocks. However, pain radiating to the buttock or trochanteric region occurred most commonly following L4 and L5 medial branch blocks, whereas groin pain was produced from L2 to L5 medial branch blocks.

Posterior pelvic pain related to the SIJ may present with a wide variety of complaints and distribution of symptoms. Gluteal pain near or surrounding the posterior superior iliac spine is the most common distribution of symptoms as described by Fortin et al. (2,3) to include buttock hypesthesia extending approximately 10 cm caudally and 3 cm laterally from the posterior superior iliac spine. In addition, pain distributions including the groin and lower extremity pain have been described to be related to SIJ pain.

Another consideration in the differential diagnosis is that extra- and intra-articular hip pain patterns overlap and the disorders can commonly coexist. For example, internal snapping hip syndrome and iliopsoas tendonitis has been described to produce anterior groin pain (22). Greater trochanteric pain syndrome has been described to cause lateral hip pain radiating down the lateral thigh (23,24). Adductor strain can cause groin and medial thigh pain at origin of pubic rami. Piriformis syndrome has been described to include buttock pain and tenderness at the sciatic notch (25).

In addition to the overlap in pain distributions, disorders of the hip, spine, and SIJ can coexist. Descriptions of the hip–spine syndrome are limited to coexisting hip and spine dysfunctions that occur in the setting of hip and spine degenerative changes noted on imaging. Reference to the coexistence of hip and spine disorders was first published by Bohl and Steffee (26). The authors described the course of six patients with continued pain after a total hip arthroplasty (THA) that was relieved with a lumbar laminectomy. In a similar study, McNamara et al. (27) described symptomatic lumbar spinal stenosis in nine patients following THA. Seven of the patients went on to have a lumbar decompression. Saunders et al. (28) evaluated 75 patients with hip OA and compared them to a control group of patients without hip OA. Lumbar spine degenerative changes were more common in the hip OA patients as compared to controls. The hip–spine syndrome term was first published by Offierski and MacNab (1) in 1983. The authors described the course of 35 patients and concluded that patients with asymptomatic lumbar spinal stenosis at the time of THA were at increased risk of neurologic injury.

Fogel and Esses (29) described the constellation of symptoms in patients considered to have hip–spine syndrome with degenerative hip disease and spinal stenosis. In a recent retrospective review by Sembrano and Polly (30), 200 patient records from a spine surgery service were evaluated. Eighty-two percent of cases reported lumbar spine pain, 12.5% of cases reported hip pain, and 14.5% reported SIJ pain. Seventeen and one-half percent reported pain in all three locations. The largest prevalence study (31) reported 17% of 3,335 people treated with hip arthroplasty were also evaluated for a lumbar spine disorder. Those with the lumbar spine disorder had significantly less improvement in pain and function following hip arthroplasty as compared to those without a lumbar spine disorder.

The first study to comment on intervention for this patient population was published by Ben-Galim et al. (32) in 2007. In this study, 25 patients were evaluated with the Harris Hip Score, Oswestry Disability Index, and visual analog scales for the hip and spine before, 2 months and 2 years after THA. All outcome measures improved after THA. The authors concluded that THA improved lumbar spine pain.