Hip Joint

The hip joint is often difficult to infiltrate or aspirate because of its depth and the surrounding tissue. Fluoroscopic guidance with injection of contrast material or ultrasound guidance is often necessary to confirm proper needle placement. This joint may be infiltrated by an anterior or lateral approach (Figs. 10-1, 10-2, 10-3). The anterior approach is preferred.^18,23,24 With the anterior approach, the patient is in the supine position with the lower extremity externally rotated. The length of the needle will depend on the patient’s size. The anatomic landmarks for the anterior approach are 2 cm distal to the anterior superior iliac spine and 3 cm lateral to the palpated femoral artery at a level corresponding to the superior margins of the greater trochanter. After superficial anesthesia is administered, the needle is advanced at an angle 60 degrees posteromedially through the tough capsular ligaments, advanced to bone, and slightly withdrawn. This technique places the tip of the needle directly into the joint, and aspiration or injection may be performed. This approach is much simpler using image guidance to direct the needle posteromedially into the joint. When the capsular ligaments have been penetrated, 2 to 4 mL of anesthetic and corticosteroid suspension may be introduced.

Figure 10-1 Intraarticular injection of the hip joint, lateral approach.

Figure 10-2 Intraarticular injection of the hip joint, anterior approach.

Figure 10-3 A, Sagittal ultrasound view of the proximal hip joint. B, Transverse ultrasound view of the proximal hip joint. A, Acetabulum; H, Femoral head; I, Iliopsoas muscle; N, Femoral neck. Arrowhead denotes the collapsed anterior joint recess. Arrow denotes the labrum.

(From Jacobson J: Fundamentals of Musculoskeletal Ultrasound, WB Saunders, 2007, p 182.)

The lateral approach is performed by palpating the greater trochanter of the femur, which may be facilitated by externally rotating the lower extremity. Superficial anesthesia may be used and, again, depending on the size of the patient, the appropriate-length needle is selected. A 3- to 4-inch needle is usually sufficient; however, in larger patients, longer needles may be necessary. Just anterior to the greater trochanter, the needle is advanced and walked medially along the neck of the femur until the joint is reached. Aspiration may be obtained but is more difficult with the lateral approach. The amount of fluid that may be introduced may be limited, depending on the integrity of the joint.

Knee

The knee is the most commonly aspirated and injected joint in the body. It contains the largest synovial space and demonstrates the most visible and palpable effusion (when present). A patient is usually most comfortable lying supine with sufficient pillows. The knee is prepared using an aseptic technique. If a large effusion is present, whether medially or laterally, the site of entry should be over the maximal expansion of the effusion in order to cause the least discomfort during the procedure. For injections in which a large effusion is not present, the lateral, medial, suprapatellar, or anterior approach may be used (Fig. 10-4). Before injecting or aspirating the knee, the patella should be grasped between the examiner’s thumb and forefinger and rocked gently from side to side to ensure that the patient’s muscles are relaxed.

Figure 10-4 A, Drawing of medial and lateral injection approaches to the knee. Surface location of a lateral (B) and medial (C) injection.

The medial approach to the knee is simple. First, the practitioner puts a small amount of lateral pressure on the patella, pushing it slightly medially and displacing it somewhat to increase the gap between the patella and the femur medially. The needle is then introduced about midway between the superior and inferior pole of the patella, medial to the patella and midway between the medial border of the patella and the femur. A preinjection skin wheal may be raised with an anesthetic agent, or the skin itself may be anesthetized with a vapo-coolant spray for patient comfort. As the needle is introduced into the joint space, the needle should be aspirated progressively. If no aspirate is obtained, the corticosteroid can be injected. Before withdrawal of the needle, the needle tract again should be flushed with a small amount of anesthetic.

The lateral approach to the knee is also simple. With the patient supine, the knee is fully extended or placed in slight flexion. The patella is slightly displaced laterally to increase the gap between the patella and femur laterally. The skin may then be anesthetized with 1% lidocaine. The needle is introduced halfway between the superior pole of the patella and the midline of the patella lateral and inferior to the patella. As the needle is introduced, aspiration is performed until the needle is inside the joint. The joint can then be aspirated or injected.

If a large effusion is present, the suprapatellar approach may be used. This does not have any specific advantage over the lateral approach unless the effusion is expanding the suprapatellar bursa. The needle is introduced at the point of maximal expansion of the effusion, and the joint is then aspirated. This approach is usually not as good as the lateral approach if the knee is to be injected only and not aspirated. It is much easier to enter the joint space with the medial or lateral approach.

On occasion, an anterior approach to the knee may be desired if a patient cannot fully extend the knee. In these cases, the patient may be sitting or supine with the knee flexed to 90 degrees. The needle is inserted just inferior to the inferior patellar pole from either the lateral or medial side of the patellar tendon. The needle is then advanced parallel to the tibial plateau until the joint space is entered. It is more difficult to aspirate a knee effusion when using this approach.²³ Moreover, the risk of puncturing the articular cartilage is much higher, as is the risk to the infrapatellar fat pad. Occasionally, the knee is approached anteriorly by inserting the needle directly through the patellar tendon. This approach has no merit because it increases discomfort to the patient and may cause bleeding in the patellar ligament.

Ankle Mortise

The ankle joint is not commonly injected; however, it may be subject to osteoarthritis, rheumatoid arthritis, or chronic pain resulting from instability.^{8,12,13,27,28} An anterior medial or anterior lateral approach may be used, depending on the location of pain or pathologic process (Figs. 10-5 and 10-6). For the medial approach, a slight depression is felt between the extensor hallucis longus tendon laterally and tibialis anterior tendon medially on the inferior border of the tibia superiorly and the talus inferiorly. The needle is then directed slightly laterally and perpendicular to the tibial joint surface. The talus has a superior curve, and the needle may need to be angled slightly superiorly to avoid contact with the talar joint surface.

Figure 10-5 A, Drawing of the different approaches to an ankle injection. Surface location of a medial (B), lateral (C), and posterior (D) sites for injections.

Figure 10-6 Ultrasound image of the ankle joint. Sagittal imaging reveals the anterior fad pad (F), between the tibia (Tib) and talus (Tal). Arrowheads depict the hyaline articular cartilage.

(From Jacobson J: Fundamentals of Musculoskeletal Ultrasound, WB Saunders, 2007, p 272.)

The lateral approach is useful in situations in which pathologic processes in the ankle appear to be most prominent either at the talofibular joint or the tibiotalar joint. Here, the foot is placed in moderate plantar flexion. The area enclosed by the tibia superiorly, the talus inferiorly, and the fibular head laterally is palpated. The extensor tendons of the toes should be medial to the injection site. The needle is then inserted from an anterolateral position and is directed toward the posterior edge of the medial malleolus. If the joint surface is encountered, the physician should direct the needle slightly upward, remembering that the talar dome arches superiorly.

Subtalar Joint

Occasionally, the subtalar joint is the site of a pathologic process.³ The easiest approach to this joint is to have the patient lie prone with his or her feet extending over the end of the examination table. This allows the ankle to be in the neutral position. The posterior and lateral portions of the ankle are then prepared aseptically. The site of entry for the injection is along a line drawn from the most prominent portion of the distal fibula posterior to the Achilles tendon. This line should be parallel to the plantar aspect of the foot with the foot in neutral position; halfway between the prominent aspect of the lateral malleolus and the Achilles tendon, the needle is inserted and directed toward a point inferior and medial to the medial malleolus. Fluoroscopic or ultrasound guidance can be very helpful during subtalar joint injections.^5.11,15,17

Intertarsal Joints

Injection of the tarsal joints may be accomplished similarly to injection of the carpal joints. Palpation of the bony landmarks is carried out, the needle is inserted between the tarsal bones to the desired depth, and aspiration is accomplished if necessary. Fluoroscopic needle guidance simplifies this procedure and ascertains precise needle placement.

Metatarsophalangeal Joints

The metatarsophalangeal joints are most frequently infiltrated with a dorsal approach (Fig. 10-7). This approach is carried out by palpating the metatarsophalangeal margins with plantar flexion of the toe to facilitate insertion of the needle. The needle is then advanced into the joint. The first metatarsophalangeal joint is frequently affected by arthritic conditions and gout. When a swollen joint is encountered, infiltration and aspiration may be easier with a swollen capsule.

Figure 10-7 Dorsal approach to the first metatarsophalangeal joint.

Conclusion

The lower extremity peripheral joints are not difficult to inject. With the use of ultrasound or fluoroscopic guidance, the clinician can become adept at entering these joints with ease, providing an effective addition to the management of peripheral joint problems.

Acknowledgment

The editor would like to extend a special thanks to John P. Obermiller, MD and Dennis M. Lox, MD for their original work on this chapter.