Origin of Long Head: Distal part of the sacrotuberous ligament and posterior part of the tuberosity of the ischium.
OriAn of Short Head: Lateral lip of the linea aspera, proximal h of the supracondylar line, and lateral intermuscular septum.
Insertion: Lateral side of the head of the fibula, lateral condyle of the tibia, deep fascia on the lateral side of the leg.
Action: The long and short heads of the biceps femoris flex and laterally rotate the knee joint. In addition, the long head extends and assists in lateral rotation of the hip joint.
Nerve to Long Head: Sciatic (tibial branch), L5, SI, 2, 3.
Nerve to Short Head: Sciatic (peroneal branch), L5, SI, 2.
Fixation: The examiner should hold the thigh firmly down on the table. (Not illustrated to avoid covering the muscles.)
Test: Flexion of the knee between 50° and 70°, with the thigh in slight lateral rotation and the leg in slight lateral rotation on the thigh.
Pressure: Against the leg, proximal to the ankle, in the direction of knee extension. Do not apply pressure against the rotation component.
Origin of Rectus Femoris
Straight head: From anteroinferior iliac spine.
Reflected head: From groove above rim of acetabulum.
Origin of Vastus Lateralis: Proximal part of intertrochanteric line, anterior and inferior borders of greater trochanter, lateral lip of the gluteal tuberosity, proximal half of lateral lip of linea aspera. and lateral intermuscular septum.
Origin of Vastus Intermedius: Anterior and lateral surfaces of the proximal 2/3 of the body of the femur, distal half of the linea aspera, and lateral intermuscular septum.
Origin of Vastus Medialis: Distal half of the in-tertrochanteric line, medial lip of the linea aspera, proximal part of the medial supracondylar line, tendons of the adductor longus and adductor magnus and medial intermuscular septum.
Insertion: Proximal border of the patella and through the patellar ligament to the tuberosity of the tibia.
Action: The quadriceps extends the knee joint, and the rectus femoris portion flexes the hip joint.
The articularis genus is a small muscle that may be blended with the vastus intermedius but is usually distinct from it. (Not shown in drawing.)
Origin: Anterior surface of the distal part of the body of the femur.
Insertion: Proximal part of the synovial membrane of the knee joint.
Action: Draws the articular capsule proximally. Nerve: Branch of the nerve to the vastus intermedius.
Patient: Sitting, with the knees over the side of the table and holding on to the table.
Fixation: The examiner may hold the thigh firmly down on the table. Alternatively, because the weight of the trunk is usually sufficient to stabilize the patient during this test, the examiner may put a hand under the distal end of the thigh to cushion that part against table pressure.
Test: Full extension of the knee joint, without rotation of the thigh.
Pressure: Against the leg, above the ankle, in the direction of flexion.
Note: Inclining the body backward may be evidence of an attempt to release hamstring tension when those muscles are contracted. When the tensor fasciae latae is being substituted for the quadriceps, it medially rotates the thigh and exerts a stronger pull if the hip is extended. If the rectus femoris is the strongest part of the quadriceps, the patient will lean backward to extend the hip, thereby obtaining maximum action of the rectus femoris.
Weakness: Interferes with stair climbing, walking up an incline, and getting up and down from a sitting position. The weakness results in knee hyperextension, not in the sense that such weakness permits a posterior knee position but, rather, that walking with a weak quadriceps requires the patient to lock the knee joint by slight hyperextension. Continuous thrust in the direction of hyperextension in growing children may result in a very marked deformity.
Contracture: Knee extension.
Shortness: Restriction of knee flexion. Shortness of the rectus femoris part of the quadriceps results in restriction of knee flexion when the hip is extended or restriction of hip extension when the knee is flexed. (See test, pp. 378, 379.)
Patient: Sitting upright, with the knees bent over the side of the table. Hold on to the table to prevent leaning backward to obtain assistance by two-joint hip flexors.
Fixation: The weight of the trunk may be sufficient to stabilize the patient during this test, but holding on to the table gives added stability. If the trunk is weak, place the patient in the supine position during the test.
Test for Hip Flexors as a Group: (Figure A) Hip flexion with the knee flexed, raising the thigh a few inches from the table.
Pressure: Against the anterior thigh, in the direction of extension.
Test for Iliopsoas: (Figure B) Full hip flexion with the knee flexed. This test emphasizes the one-joint hip flexor by requiring completion of the arc of motion. The grade is based on the ability to hold the completed position. With weakness of the iliopsoas, the fully flexed position cannot be held against resistance, but as the thigh drops to the position assumed in the group test, the strength may grade normal. This test is used to confirm the findings of the supine test, which is described on the facing page.
Pressure: One hand against the anterior shoulder area gives counterpressure, and the other applies pressure against the thigh, in the direction of hip extension.
Note: Lateral rotation with abduction of the thigh as pressure is applied generally is evidence of sar-torius strength or of a tensor fasciae latae that is too weak to counteract the pull of the sartorius. Medial rotation of the thigh shows the tensor fasciae latae as stronger than the sartorius. If adductors are primarily responsible for the flexion, the thigh will be adducted as it is flexed. If the anterior abdominals do not fix the pelvis to the trunk, the pelvis will tilt anteriorly to flex on the thighs, and the hip flexors may hold against strong pressure, but not at maximum height.
Weakness: Decreases the ability to flex the hip joint, and results in marked disability in stair climbing or walking up an incline, getting up from a reclining position, and bringing the trunk forward in the sitting position preliminary to rising from a chair. With marked weakness, walking is difficult, because the leg must be brought forward by pelvic motion (produced by anterior or lateral abdominal muscle action) rather than by hip flexion. The effect of hip flexor weakness on posture is shown on pages 68, 72.
Contracture: Bilaterally, hip flexion deformity with increased lumbar lordosis. (See p. 223, Figure A.) Unilaterally, hip position of flexion, abduction, and lateral rotation.
Shortness: In the standing position, shortness of the hip flexors is seen as a lumbar lordosis with an anterior pelvic tilt.
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