Hip Diagnosis and Decision-Making

Soft Tissue Injuries

Inflammation and pain originating from the trochanteric, ischial, iliopsoas, and iliopectineal bursae are common. Movement at bone and soft tissue interfaces leads to repetitive friction and inflammation in these areas. Trochanteric bursitis is frequently diagnosed but may be more accurately described as greater trochanteric pain syndrome (GTPS). Magnetic resonance imaging (MRI) findings for this diagnosis have shown frequent abductor tendinitis and tears with bursitis lacking in up to 80% of patients. Nonetheless, patients with trochanteric bursitis describe lateral thigh pain that can be reproduced with palpation on examination. Ischial bursitis typically presents with pain upon sitting and can be reproduced by palpation over the ischial tuberosity (IT). The iliopsoas bursa lies between the iliopsoas muscle and pelvic brim. Patients typically present with inguinal pain that is reproducible with provocative maneuvers such as the Thomas test. The iliopectineal bursa is adjacent to the iliopsoas bursa but lies over the iliopectineal eminence. Symptoms are similar to those of iliopsoas bursitis, although iliopectineal bursitis can be seen in conjunction with a snapping iliopsoas muscle over the iliopectineal eminence.

Snapping hip syndrome, also referred to as coxa saltans , causes an audible or palpable “snap” with hip range of motion (ROM). The etiology of a snapping hip is classified as external, internal, or intra-articular. An external snapping hip is caused by the iliotibial band (ITB) passing over the greater trochanter. An internal snapping hip is attributed to shifting of the iliopsoas tendon from medial to lateral over the femoral head, iliopectineal eminence, iliacus muscle, or lesser trochanter among others during hip flexion and extension. An intra-articular snapping hip is related to labral tears, loose bodies, or osteochondral injuries.

Contusions involving the hip, thigh, and pelvis are frequently encountered in athletes and occur after low-energy trauma. An iliac crest contusion, or “hip pointer,” results from a direct blow to the iliac crest, and an overlying hematoma often develops. Quadriceps contusions typically involve a direct blow to the anterior thigh, which can result in hematoma formation and difficulty ambulating. A direct blow to the inner thigh may result in a groin contusion. Myositis ossificans can occur after a contusion and hematoma. The hematoma organizes and calcifies, which can lead to pain and stiffness. Myositis ossificans can also be seen in the absence of trauma.

Muscle strains and ligamentous injuries around the hip can be quite debilitating. Strains typically involve tearing at the musculotendinous junction and often occur during an eccentric contraction. Strains are classified by the affected muscle groups, including adductor, iliopsoas, external oblique, hamstring, and quadriceps. With significant force during athletics, or in the setting of trauma, the strong sacroiliac ligaments can be sprained. Pain typically originates in the lower back and radiates into the buttock or groin.

Hernias involve the extrusion of abdominal contents through a defect in the abdominal wall. A delay in diagnosis is common because hernias can mimic other conditions that cause groin pain with activity. Three hernias can present as hip or pelvic pain: inguinal, femoral, and sports hernias. Inguinal hernias involve the protrusion of abdominal contents through the deep inguinal ring or medial to the deep inguinal ring. Femoral hernias occur when a hernia sac protrudes through the femoral sheath to enter the anterior thigh. The “sports hernia” or athletic pubalgia is an increasingly recognized condition caused by posterior inguinal/abdominal wall weakness or tearing in athletes. No true protrusion of abdominal contents occurs, but patients experience chronic groin pain that is often difficult to diagnose. The pain can also radiate to the perineum and origin of the adductors. Sports that require frequent pivoting and cutting such as ice hockey, soccer, and American football have the highest incidence of this injury. Athletes often lack symptoms with rest but experience pain with activity or sport that prevents them from playing to their potential.

Bone Injuries

Sport-related trauma can involve significant energy resulting in fractures of the pelvis and femur. Pelvic ring injuries, acetabular fractures, femoral head and neck fractures, peritrochanteric fractures, and femoral shaft fractures lead to the acute onset of pain and difficulty or inability to weight bear or ambulate. Prompt recognition and treatment of fractures about the pelvis and femur are critical, as delay in diagnosis can result in long-term morbidity.

Stress fractures of the pelvis and femur occur in the setting of repetitive submaximal loading of bone. Pain that is aggravated by activity and subsides with rest is the hallmark feature of a stress fracture. Pelvic rami and sacral stress fractures are seen in athletes who participate in high-impact activities such as running and jogging. The pain is typically in the groin, buttock, or thigh when the ramus is involved and in the low back when the sacrum is the source. Femoral neck stress fractures typically present with activity-related groin pain. The location of the stress fracture is critical to determining treatment. Tension-sided femoral neck stress fractures along the superior lateral neck require surgical treatment to prevent nonunion, avascular necrosis, or fracture displacement. Compression-sided femoral neck stress fractures occur along the inferior medial neck and are often amenable to nonoperative treatment.

A stress injury of the pubic symphysis can lead osteitis pubis. This is frequently secondary to a muscular imbalance between the rectus abdominis (pelvic elevator) and the adductor tendons (pelvic depressor) that attach to fibrocartilage plate of the pubic symphysis. The pain is typically insidious in onset and is located at the midline over the symphysis or referred to the groin. Degeneration of the symphyseal cartilage can be followed by boney lytic changes, sclerosis, and widening of the symphysis.

Osteonecrosis, or avascular necrosis, of the femoral head is a cause of hip pain in young adults. Many conditions have been associated with osteonecrosis; however, the majority are related to corticosteroid use, trauma, alcohol abuse, and coagulopathy. No cause is identified in 10% to 20% of cases, and this type of necrosis is termed “idiopathic avascular necrosis.” Patients typically present with pain in the groin or buttock and often walk with a limp. Bilateral avascular necrosis has been found in 40% to 80% of patients. Early identification may allow treatment that can prevent femoral head collapse and the need for arthroplasty.

Instability

Hip dislocations typically occur when significant force disrupts the soft tissue restraints of the hip joint. However, low-energy injuries may also cause hip dislocations in the setting of femoroacetabular impingement (FAI) morphology (cam, pincer, acetabular retroversion). Clinical and basic science studies support the mechanism of the anterior impingement levering the femoral head posteriorly. Hip dislocations are typically posterior, which leads to the patient having a shortened, internally rotated, and abducted hip. Less commonly, the dislocation will be anterior, which presents as an externally rotated and abducted hip. Expeditious recognition and reduction may be essential to prevent avascular necrosis.

Microinstability of the hip is a more recent, but increasingly recognized, cause of hip pain. Several predisposing factors have been identified and include: generalized ligamentous laxity, repetitive microtrauma, ligamentum teres (LT) injuries, varying degrees of acetabular dysplasia, and iatrogenesis. Soft tissue and dynamic stabilizers of the hip such as the capsule, labrum, LT, and tendinous structures such as the iliopsoas may all play a role in microinstability. The clinical presentation may be subtle and difficult to detect. Most patients complain of pain in the groin, buttock, or thigh, but some may note “giving way” or apprehension. The onset is insidious with gradual worsening of symptoms.

Degenerative Joint Disease

Degenerative joint disease (DJD) results from the loss of cartilage in the hip joint and leads to progressive pain and stiffness. Many pathologic processes can lead to DJD, including but not limited to osteoarthritis, rheumatoid arthritis, avascular necrosis, infection, trauma, FAI, and dysplasia/instability. Although the process may be idiopathic, we now recognize that structural abnormalities of the hip are frequently associated with DJD. The diagnosis is usually confirmed by observing joint space narrowing, subchondral cysts and/or sclerosis, and/or osteophyte formation on plain radiographs. Patients typically present with the insidious onset of hip pain that worsens with activity.

DJD is a spectrum and ranges in severity. While advanced DJD is usually obvious, milder forms of DJD may be more ambiguous. It is crucial to determine how much joint degeneration is present, as this can have dramatic implications on treatment and surgical outcomes. In addition to plain x-rays, delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) can provide a helpful quantitative analysis of the articular cartilage health. An algorithm ( Fig. 77.1 ) helps stratify patients by degree of arthritis and the appropriate respective treatments.

Nerve Entrapment Injuries

Nerve entrapment surrounding the hip can involve the sciatic, obturator, pudendal, ilioinguinal, femoral, and lateral femoral cutaneous nerve. Diagnosing and treating these conditions can be difficult and frustrating for the patient and clinician. The pain often has a burning quality and is confined to a nerve root distribution. Electromyographic nerve conduction studies are helpful in confirming the diagnosis and ruling out a lumbar radiculopathy. Sciatic nerve entrapment often presents with pain radiating down the buttock and posterior thigh. In some cases, this pain may be related to piriformis syndrome. Obturator nerve entrapment causes pain in the medial thigh that can radiate toward the knee. Prolonged compression during activities such as cycling can cause pudendal nerve entrapment. Numbness and pain in the perineum and shaft of the penis are typical. Ilioinguinal nerve entrapment is a very rare cause of inguinal pain that often radiates into the groin. Pain over the anterior thigh can be caused by femoral nerve entrapment, and when severe, it may cause quadriceps weakness and difficulty with gait. Lateral femoral cutaneous nerve entrapment, or meralgia paresthetica , causes anterolateral thigh pain and numbness that extends toward the lateral knee.

Intra-Articular Pathology

Our understanding of intra-articular pathology has significantly expanded during the past few decades. Structural abnormalities of the hip joint seen in persons with dysplasia and FAI often lead to injury of the labrum and chondral surface. Hip dysplasia, or developmental dysplasia of the hip, results in a broad spectrum of disease. The underlying abnormality is inadequate acetabular coverage of the femoral head, which in severe forms can cause hip dislocations in children. Often the degree of undercoverage is mild or “borderline” and leads to pathology during adulthood because of the concentration of forces on a shallow acetabulum. FAI is caused by abnormalities of the femur and acetabulum that lead to abnormal contact within the hip joint. Deformity on the femoral side is termed cam impingement and is due to an aspherical femoral head commonly located at the anterosuperior head-neck junction. Deformity on the acetabular side is termed pincer impingement and occurs with excessive acetabular coverage of the femoral head. Most commonly, both abnormalities exist in the same hip joint, and this condition is termed combined impingement . Iliopsoas impingement is compression and damage to the underlying anterior acetabular labrum at the 3 o'clock position (right hip) by a tight iliopsoas tendon or an inflamed tendon adherent to the anterior capsulolabral complex causing a repetitive traction injury to the labrum. This differs from the typical 1 to 2 o'clock labral tear distribution seen in FAI. Patients with intra-articular pathology typically present with groin, lateral hip, or buttock pain. Scrutinizing hip radiographs will often help the clinician identify morphologic abnormalities of the hip that may lead to intra-articular pathology. Multiple other sources of intra-articular pathology have also been described, such as ruptured LT, loose bodies, and synovial disease.

Infection

Septic arthritis of the hip should always be considered in a patient who presents with the acute onset of pain. The patient is often febrile and lacks a history of trauma. Physical examination reveals pain with attempted passive ROM. Inflammatory markers are typically elevated. Prompt recognition and treatment are necessary to prevent long-term complications.

Pediatric Hip Conditions

Skeletally immature patients often present with hip conditions that differ from the hip conditions of adults. Open physes and apophyses are areas of weakness and are frequently injured. When muscles are overloaded in children, failure can occur at the origin of the muscle, particularly when an apophysis is present. This scenario causes an avulsion fracture at the muscle origin, which differs from the pathology seen in adults, who most frequently experience a soft tissue tear of involving the tendon. Males account for up to 86.7% of these injuries. Avulsion fractures occur most commonly at the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), and IT, when the sartorius/tensor fasciae latae, rectus femoris, hamstrings, and iliopsoas muscles, respectively, are overloaded. Lateral and distal displacement of ASIS injuries can be misdiagnosed as AIIS avulsions. Patients with IT avulsions tend to be younger due to earlier ossification center formation and 12% will have a contralateral sided injury. Less common avulsion injuries include the iliac crest, pubic symphysis, and lesser trochanter with muscle forces from the abdominal muscles, adductors, and iliopsoas, respectively. If misdiagnosed or delayed in presentation, these injuries can lead to hip impingement or nerve irritation and exhibit the respective symptoms.

Slipped capital femoral epiphysis (SCFE) is a disorder of the proximal femoral physis. The proximal femoral physis fails, leading to anterior superior displacement of the femur relative to the epiphysis. This condition typically involves patients 11 to 14 years of age, often affects obese children, and may be seen in the setting of endocrine abnormalities. Displacement at the physis can frequently be identified with a frog-leg lateral radiograph. Duration of symptoms and stability at the physis is important for treatment and prognosis. Patients with an unstable slip are unable to weight bear and have approximately a 50% chance of AVN. When SCFE is identified, surgical treatment is often indicated.

Legg-Calvé-Perthes disease (LCPD) is a childhood disorder that leads to ischemic necrosis of the growing femoral head. The process typically affects patients 5 to 8 years of age and predominantly involves boys. Like SCFE, there may also be an association with obesity. Parents notice that the child is limping, but the patient often has only mild pain. Radiographs can identify abnormalities in the femoral epiphysis.