1. Sites of Injection: Anterolateral part of the mid-thigh
Muscle targeted: Vastus Lateralis
Origin: Greater trochanter and linea aspera of femur
Insertion: Patella via quadriceps tendon and then tibial tuberosity via patellar ligament
Action: Extend leg at knee joint; flexes thigh at hip joint
Locating Area of the Muscle: Palpate the muscle below the greater trochanter and above the lateral femoral condyle. The injection should be administered into the middle third part of the muscle, on the lateral side of the thigh.
2. Preferred Muscle for IM Injection: Deltoid Muscle
Origin: Acromial extremity of clavicle, acromion of scapula, and spine of scapula
Insertion: Deltoid tuberosity of humerus
Action: Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint.
Locating Area of the Muscle: Palpate the muscle and feel for the central and thickest portion of the deltoid muscle–about 2-3 fingerbreadths below the acromion process and above the level of the armpit.