The hip joint is a synovial joint that provides the interface between the axial skeleton and pelvis weightbearing lower extremities. The joint comprises the articulation between the spheroid head of the femur and the socket-like acetabulum (Fig. 115.1). The joint’s articular cartilage is susceptible to damage, which, if left untreated, will result in arthritis with its associated pain and functional disability. Osteoarthritis of the joint is the most common form of arthritis that results in hip joint pain and functional disability, with rheumatoid arthritis and posttraumatic arthritis also causing arthritis of the hip joint (Fig. 115.1). Less common causes of arthritis-induced hip joint pain include the collagen vascular diseases, infection, villonodular synovitis, and Lyme disease. Acute infectious arthritis of the hip joint is best treated with early diagnosis, with culture and sensitivity of the synovial fluid, and with prompt initiation of antibiotic therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the hip joint, although hip pain secondary to the collagen vascular diseases responds exceedingly well to ultrasound-guided intra-articular injection of the hip joint.

Patients with hip joint pain secondary to arthritis, tears of the fibrocartilaginous labrum, and collagen vascular diseaserelated joint pain complain of pain that is localized to the hip and proximal lower extremity. Activity makes the pain worse, with rest and heat providing some relief. The pain is constant and characterized as aching. Sleep disturbance is common with awakening when the patient rolls over onto the affected hip. Some patients complain of a grating, catching, or popping sensation with range of motion of the joint, and crepitus may be appreciated on physical examination.

Functional disability often accompanies the pain associated with many pathologic conditions of the hip joint. Patients will often notice increasing difficulty in performing their activities of daily living, and tasks that require walking, climbing stairs, and getting in and out of cars are particularly problematic. If the pathologic process responsible for the patient’s pain symptomatology is not adequately treated, the patient’s functional disability may worsen, and muscle wasting and ultimately a frozen hip may occur.

Plain radiographs are indicated in all patients who present with hip pain as not only intrinsic hip disease as well as other regional pathology may be perceived as hip pain by the patient (Fig. 115.2). Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. MRI or ultrasound of the hip is indicated if avascular necrosis or labral tear is suspected.

The hip joint comprises the articulation between the spheroid head of the femur and the cup-shaped acetabulum of the hip (see Fig. 115.1). The articular surface of the hip joint is covered with hyaline cartilage, which is susceptible to arthritis from a variety of causes. Because the vascular supply to the articular cartilage is tenuous, the hip joint is especially susceptible to avascular necrosis (Fig. 115.3). Approximately 50% of the head of the femur rests within the acetabulum with a fibrocartilaginous layer called the acetabular labrum adding additional stability to the joint (see Fig. 115.1). The labrum is susceptible to degenerative changes as well as trauma should the femur be subluxed or dislocated. The hip joint is surrounded by a dense capsule that allows the wide range of motion of the hip joint while preventing subluxation. The joint capsule is lined with a synovial membrane that attaches to the articular cartilage. This membrane gives rise to synovial tendon sheaths and bursae that are subject to inflammation. The hip joint is innervated by the femoral, obturator, and sciatic nerves. The major ligaments of the hip joint include the iliofemoral, pubofemoral, ischiofemoral, and transverse acetabular, which along with the labrum and joint capsule provide strength to the hip joint (Fig. 115.4). The muscles of the hip and their attaching tendons are susceptible to trauma and to wear and tear from overuse and misuse.

The benefits, risks, and alternative treatments are explained to the patient, and informed consent is obtained. The patient is then placed in the supine position with the lower extremity slightly externally rotated (Fig. 115.5). The skin overlying the hip joint is then prepped with antiseptic solution. A sterile syringe containing 2.0 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 3½-inch, 22-gauge needle using strict aseptic technique. A curvilinear low-frequency ultrasound transducer is placed over the proximal femur in the longitudinal plane with the transducer parallel to the femur (Fig. 115.6). A survey scan is taken, which demonstrates the femur as a linear hyperechoic structure (Fig. 115.7). The medial margin of the femur is identified. The ultrasound transducer is then slowly moved toward the head of the femur following the medial margin of the femur until hyperechoic margin of the femur swings sharply upward at the junction of the femoral neck and the femoral head (Fig. 115.8). At the junction of the medial margin of the femoral neck and femoral head is the joint space, which is amenable to injection (Fig. 115.9). The hip joint is then identified as a hypoechoic fluid-containing structure at the “V” of the junction of the femoral neck and head. After the joint space is identified, the needle is placed through the skin ˜1 cm below the inferior


end of the transducer and is then advanced using an in-plane approach with the needle trajectory adjusted under real-time ultrasound guidance to enter the hip joint at the “V” of the junction of the femoral neck (Fig. 115.10). When the tip of the needle is thought to be within the joint space, a small amount of local anesthetic and steroid is injected under realtime ultrasound guidance to confirm intra-articular placement by the characteristic spreading swirl of hyperechoic injectate within the joint. After intra-articular needle tip placement is confirmed, the remainder of the contents of the syringe are slowly injected. There should be minimal resistance to injection. If synechiae, loculations, or calcifications are present, the needle may have to be repositioned to ensure that the entire intra-articular space is treated. The needle is then removed, and a sterile pressure dressing and ice pack are placed at the injection site.