Lower extremity intraarticular injections with corticosteroids and anesthetics are useful treatment options for patients with hip, knee, ankle, or foot pain. Injections are given to treat acutely painful joints refractory to rest and oral medications. The indications, patient selection, complications, and general technique of joint injections were covered in the previous chapter. This chapter will focus on the technique of specific lower extremity intraarticular joint injections. Knowledge of multiple techniques is helpful.
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. 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is advanced at an angle 60 degrees posteromedially through the tough capsular ligaments, advanced to bone, and slightly withdrawn.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.
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.
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.
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. 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.