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Orthopedics 108 THE FUNCTIONAL ANATOMY OF THE POSTERIOR THIGH AND GLUTEAL MUSCULATURE Instructor: J. Kim Ross, BSc, MSc, DC, Ph.D.

Note: This is a portion of the one-hour course, Ortho 108, offered on www.ChiroCredit.com for continuing education credit. To better understand the manner in which the foot and ankle functions, it is essential to be familiar with the functional anatomy of the muscles of the lower limb, and their role in gait. It is important to realize that there are two main types of muscle contraction. There is concentric contraction, where muscle is active during shortening and there is eccentric contraction where the muscle is active during lengthening. Hence concentric contraction causes movement of body parts in the same direction as the muscle is contracting, while eccentric contractions simply act as a “brake” and slow down movements that are occurring in the opposite direction to which the muscle pulls when it is shortening. Most people think of the significance of concentric contractions when looking at the function of a muscle. However, eccentric contractions are just as important especially in the gait cycle. We will begin with the role of the posterior thigh and gluteal region musculature. The significant muscles are: • • • •

Gluteus maximus Gluteus medius Gluteus minimus Hamstrings

Gluteus maximus This muscle originates from ilium behind the posterior gluteal line and sacrotuberous ligament and inserts on the gluteal tuberosity of the the femur and iliotibial band (figure 1).

The force vector point of application is therefore posterior to the hip joint, acting in a superior and medial direction. It therefore extends the hip and rotates the femur externally. The role during gait is three-fold: • • •

During late swing, it acts eccentrically, to decelerate flexion of the hip. During early stance it acts concentrically to initiate extension of the hip. At toe-off it acts concentrically to assist in abducting the swing phase leg.

Gluteus medius This muscle originates from the outer ilium and crest between the inferior and posterior gluteal lines and inserts into the lateral side of the greater trochanter (figure 2).

Because it inserts superior to the hip it abducts the thigh. Anterior fibres are attached anterior to the hip and hence result in internal rotation of the thigh while posterior fibres are attached posterior to the hip and hence result in external rotation of the thigh. It has one main and a seconday role during gait: •

It acts as a frontal plane stabilizer. Peak activity occurs during early midstance as the muscle attempts to prevent the pelvis on the swing side from excessive lowering.

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There is also a brief burst at toe-off possibly assisting abduction and internal rotation of the femur during early swing.

ASSIGNMENT: Stand on one leg and palpate the region shown in figure 2 on the stance leg side. You should feel a contracted gluteus medius muscle. Patients who have osteoarthritis of the hip, walk with a unique but paradoxical motion. One would think that a patient would lean away from the painful hip. However the patient will generally lean the upper torso over the symptomatic hip. The purpose of this adaptation is to move the centre of mass of the torso directly over the hip. In this way gluteus medius has little work to do to counter a moment that would cause the pelvis to fall on the swing leg side. If gluteus medius is relatively inactive, the patient will avoid the tremendous hip joint compression associated with the activity of gluteus medius. Gluteus minimus This muscle originates from the outer ilium between the anterior and inferior gluteal lines and inserts into the anterior border of the greater trochanter (figure 3).

Due to its anterior attachment it internally rotates the femur. Due to the fact that it inserts superior to the hip joint, it also abducts the femur. Its role during gait: • •

It acts synergistically with gluteus medius during early stance Burst of activity during midswing allows continued internal rotation of the femur.

Hamstrings

The hamstrings are composed of : • • •

Biceps femoris Semitendinosus Semimembranosis

The Biceps femoris originates on the inner medial ischial tuberosity and sacrotuberous ligament, and inserts onto the head of the fibula and lateral condyle of the tibia. Since it acts posterior to the hip, it extends the femur. Since it acts posterior to the knee, it flexes the leg (figure 4).

The Semitendinosis originates from the lower medial ischial tuberosity and inserts into the medial body of the tibia. Like biceps femoris it extends the femur and flexes the knee (figure 5).

The Semimembranosis originates from the upper outer ischial tuberosity and inserts into the posterior medial aspect of the tibial condyle. Its actions are the same as the other two hamstrings (figure 6).

Their role during gait is the following: •

They demonstrate peak activity during the terminal portion of swing phase, during which they decelerate the forward motion of the extending leg (eccentric activity).

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They contract through most of the contact period where they assist gluteus. maximus with decelerating flexion (eccentric activity) and initiating extension of the hip joint (concentric activity).

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A burst of activity during late propulsion may act to assist gastrocnemius with flexing the knee.

The phase of gait in which each of the aforementioned muscles is active is shown in figure 7.

Clinical Conditions of the Posterior Thigh and Gluteal Region Muscles Hamstring Strains These are associated with: • • • • •

Poor flexibility Inadequate warm-up Fatigue Deficiency in the reciprocal actions of opposing muscle groups Imbalance between hamstrings and quadricep strength

The signs and symptoms are: • • •

A “pop” or “snap” with immediate loss of function There may be a palpable lump or hematoma If severe strain has a tendancy to occur at the origin or insertion

Treatment: • • • • • • •

Do not try to “run out” a hamstring strain Elastic wrap and ice bag should be applied Ultrasound once the acute phase is over Once acute phase is over, athlete may work through an active range of motion while in chest deep water When soreness is gone, athlete begins some knee curls, leg extensions and high speed cycling Finally light massage to break up adhesions Manipulation if deemed necessary to the sacroiliac joints

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When the athlete returns to sport, they should wear an elastic support around the thigh to keep the area warm and reduce swelling

Prognosis • • •

Mild strains heal in a few days to a week Moderate strains heal in 1-3 weeks Avulsion fractures at the ischial tuberosity or fibular head take a month or more to heal

References Michaud, T. (1993) Foot Orthoses and Other Forms of Conservative Foot Care. Williams & Wilkins Pansky, B.(1984) Review of Gross Anatomy. Macmillan Publishing Co. 5th ed. Kulund, D.(1982) The Injured Athlete. J.B. Lippincott Co.

IMPORTANT NOTE: This course is part of the information available in the Continuing Education Course Ortho 108 on www.chirocredit.com. To take the complete course for continuing education credit, please go to www.ChiroCredit.com and login if you are currently a registered user, or take a moment and register for free.