Lumbar Spine, Hip and Knee

Written Learning Objectives

1. Understand the organization of the lumbar portion of the vertebral column.

There are 5 lumbar vertebrae, and these are considerably more robust than the cervical or thoracic types. L5 articulates with the base of the sacrum; thus, the lumbar spinal column is attached to the pelvic girdle.

Between the bodies of the vertebrae are intervertebral discs (symphyses - cartilaginous joints). These discs are composed of an outer, fibrous ring (anulus fibrosus) and the deep nucleus pulposus. There are intervertebral discs between all the lumbar vertebrae and between L5 and S1. The nucleus pulposus is considerably thicker anteriorly than posteriorly.

The highest frequency of disc herniations/protrusions occur at the L4/L5 or L5/S1 levels, and occur in a posterolateral direction. Acute herniations may be comorbid with intervertebral foramina narrowing that can compress spinal nerves or roots.

Disc herniation and intervertebral foramina narrowing are among the many possible causes of lower back pain.

The sacro-iliac joints posterior joints of the hip girdle formed by the articulation of the auricular surfaces of the ilia and sacrum. This is a compound joint with both a synovial (anterior) component and a syndesmosis/fibrous (posterior) component. This is one of the strongest, weight-bearing joints of the body, which is supported by many strong ligaments and only allows a limited amount of movement.

2. Describe the muscles of the gluteal/hip region, and discuss the function of each with particular attention to the role in locomotion. Consider the effect a lesion would have on the nerves and the muscular compartments they serve.

The muscles of the gluteal and hip region primarily take origin from the posterior surface of the ilium (iliac blade) and posterior portion of the ischium. They all cross the hip and insert onto the proximal femur, and act on the hip joint.

Click here to download a PDF of all individual muscle tables.

Click here to download a PDF of the comprehensive muscle table. 

*Students are only responsible for muscles discussed in the main text of the learning objectives and/or list of structures


There are 3 gluteal muscles:

The gluteal muscles are arranged in three layers all taking origin from the posterior surface of the iliac blade. The gluteus maximus m. is most superficial, has the largest surface area, and overlies all of the muscles of the gluteal and hip region. Deep to the superior portion of the gluteus maximus is the gluteus medius m., and deep to the medius is the gluteus minimus m. lying directly on the posterior surface of the ilium.

The gluteus maximus m. is a powerful extender of the hip joint and the gluteus medius and minimus mm. are abductors of the thigh at the hip joint. All are involved in locomotion: maximus especially for climbing stairs or inclines and for rising from a sitting or squatting position; medius and minimus function to keep the pelvis from dropping on the unsupported side when only one leg is supporting the body – the abductors contract on one side to keep the pelvis from falling or dropping on the other side when the leg is not supporting it; eg during the normal walking cycle.

Deep muscles:

Deep to the gluteus maximus m., and inferior to the gluteus medius and minimus mm. is the piriformis m. It originates inside the pelvic cavity, taking origin from the anterior surface of the sacrum. It exits through the greater sciatic foramen of the pelvis (having a very close relationship to the sciatic n.) and inserts on the greater trochanter of the femur.


Inferior to the piriformis mm. are several hip rotators: obturator internus, superior and inferior gemelli mm., and quadratus femoris m. These muscles take origin from the ischium, insert onto the proximal femur, and laterally rotate the hip.

3. Describe the neurovascular supply of the gluteal region.

The superior and inferior gluteal neurovasculature supply the gluteal muscles. These neurovascular structures originate in the pelvic cavity and travel through the greater sciatic foramen to supply the gluteal muscles of the posterior gluteal region. The superior gluteal neurovasculature exits the greater sciatic foramen superior to piriformis m., travels between the gluteus medius and minimus mm., and sends branches to supply these muscles. The inferior gluteal neurovasculature exits the greater sciatic foramen inferior to piriformis m. with the sciatic n. and supplies the gluteus maximus m.


The superior and inferior vessels are branches of the internal iliac a. and v., and the nerves are branches of the lumbosacral plexus that forms on the anterior surface of the sacrum within the pelvic cavity.

The superior and inferior gluteal nn. and vessels are named based on their relationship to the piriformis m. as they travel through the greater sciatic foramen; superior gluteal n. and vessels exit superior to the piriformis m., inferior gluteal n. and vessels exit inferior to the piriformis m. The superior gluteal n. and vessels supply the gluteus medius and minimus mm., while the inferior gluteal n. and vessels supply the gluteus maximus m. The piriformis m. and lateral rotator mm. are supplied by nerves derived from the lumbosacral plexus. The blood supply to the piriformis m. and lateral rotator mm. is primarily from inferior gluteal a., with additional supply from superior gluteal for the piriformis m.

4. Identify the major joint and associated ligaments in the hip region. Explain what kind of movements occur at the joints and other pertinent information.

Movement Videos

The hip joint is a synovial, ball and socket joint, and is the second most mobile joint in the body (2nd to the glenohumeral joint - both ball & socket joints). The joint is formed by the acetabulum of the coxal bone and head of the femur. Medial and lateral rotator muscles of the thigh play an important role in support and structure of the hip joint.

Accessory structures of hip joint:

5. Describe the blood supply to the hip joint and possible clinical concerns associated with this blood supply.

The hip joint is supplied by arteries branching from the deep femoral a. – the medial and lateral circumflex femoral aa. They encircle the neck of the femur and provide collateral supply to the joint, including the femoral head. Occasionally, the circumflex femoral aa. arise directly from the femoral a., not the deep femoral a. The circumflex femoral vessels are vulnerable to damage if the femoral head is dislocated or the femoral neck is fractured. If the blood supply to the joint is compromised, avascular necrosis may occur.

6. Describe the organization of the neurovasculature in the popliteal fossa.

The popliteal fossa is bounded by hamstring muscles superiorly and the two heads of gastrocnemius m. inferiorly. It is filled with a large amount of adipose tissue.

The neurovasculature is organized in this manner (superficial to deep):

The popliteal vein and artery are tightly packaged in connective tissue and may look like one structure when first uncovered during dissection.

7. Describe the knee joint, including associated ligaments and tendons that assist in supporting the joint. Understand the typical organization of bursae in this region.

The knee joint is a modified hinge joint which is capable of a small degree of medial and lateral rotation, particularly from a flexed position. The knee joint is actually a complex of 3 articulations: patellofemoral and lateral & medial tibiofemoral joints. When observing the articular surfaces of the medial and lateral condyles of the femur and tibia, one can observe the notable incongruence of the articulation structures. Due to this incongruence, accessory structures are vital to the structural integrity of this joint. 

Accessory structures of knee joint: