Canine Pelvic Limb Anatomy Quiz

The iliopsoas muscle consists of the psoas major and iliacus. The psoas major originates from lumbar vertebrae, while the iliacus originates from the iliac fossa. Both converge to insert at the lesser trochanter of the femur. This anatomical alignment positions the muscle anterior to the hip joint, allowing effective hip flexion by decreasing the angle between the femur and pelvis during contraction.

The long digital extensor originates from the extensor fossa of the femur and inserts on the extensor processes of distal phalanges of digits II–V. Its tendon passes over the cranial tarsus, allowing it to extend the digits and flex the tarsal joint. The muscle’s position anterior to these joints determines its mechanical advantage during limb protraction.

The peroneus longus originates from the lateral condyle of the tibia and proximal fibula, inserting on the fourth tarsal bone and metatarsal bases. Its lateral placement allows medial rotation of the paw. Because its tendon crosses the tarsal joint anteriorly, contraction produces tarsal flexion, aiding limb positioning during stance and locomotion stabilization phases.

The lateral digital extensor originates from the head and proximal third of the fibula. It inserts on digit V. Due to its lateral anatomical placement, contraction extends and slightly abducts the fifth digit. Since it crosses the tarsus cranially, it assists in flexion of the tarsal joint during limb advancement in the swing phase.

The gastrocnemius originates from the medial and lateral supracondylar tuberosities of the femur and inserts on the tuber calcanei via the common calcaneal tendon. It crosses both stifle and tarsal joints. Contraction extends the tarsus and flexes the stifle. Its biarticular nature enhances propulsion by transmitting force from femur to calcaneus efficiently.

The deep digital flexor originates from the caudal tibia, fibula, and interosseous membrane and inserts on the distal phalanges. Because it runs caudal to the tarsal joint, it extends the tarsus and flexes the digits. Its long tendon enables controlled digital flexion during weight support and locomotion, providing strong gripping capability.

The quadratus lumborum originates from the last ribs and lumbar transverse processes. Its attachment to lumbar vertebrae allows stabilization and lateral flexion of the spine. Because it spans multiple vertebral segments, contraction fixes the lumbar column during hindlimb movement, preventing excessive spinal deviation and maintaining coordinated locomotion.

The iliopsoas includes the psoas major and iliacus. Both attach to the lesser trochanter after originating from lumbar vertebrae and ilium respectively. Since the muscle passes cranial to the hip joint, contraction produces hip flexion. Its positioning provides powerful limb advancement during gait initiation and coordinated pelvic limb movement.

The cranial tibial muscle originates from the lateral condyle and proximal lateral surface of the tibia. It inserts on the plantar surface of the base of metatarsals I and II. Because it crosses the cranial aspect of the tarsal joint, contraction produces dorsiflexion, also termed flexion of the tarsus, and contributes to lateral rotation of the paw.

The superficial digital flexor originates from the lateral supracondylar tuberosity of the femur and inserts on the tuber calcanei and middle phalanges. Positioned caudally, it flexes the digits and extends the tarsus. By spanning multiple joints, it supports weight-bearing and stabilizes the limb during stance, particularly when resisting hyperflexion forces.

The popliteus originates from the lateral condyle of the femur and inserts on the caudal proximal tibia. It acts as a stifle flexor and medial rotator of the tibia. Its oblique fiber orientation allows rotational adjustment of the tibia during flexion, contributing to joint stability and controlled unlocking of the stifle.

The psoas minor attaches to the ventral surfaces of T13 to L5 and inserts on the iliopectineal eminence. It does not cross the hip joint significantly. Instead, it stabilizes and flexes the lumbar vertebral column while steepening the pelvis. Its anatomical alignment supports posture maintenance rather than limb propulsion.