Hamstring Length Apparently Short Actually Normal

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Short hip flexors hold back in hyperexlension and hip joint flexion

In the supine position with the legs extended, low back hyperextended, and pelvis in anterior tilt, the hipjoint is already in flexion. If the straight-leg-raising test is performed with the low back and pelvis in this position, hamstrings of normal length will appear to be short.

With few exceptions, the position of anterior tilt results from shortness of the one-joint hip flexors, and the amount of flexion varies with the amount of hip flexor shortness.

If it were possible to determine how many degrees of hip flexion exist by virtue of the pelvic tilt, this number could be added to the number of degrees of straight-leg raise in determining hamstring length. It is not possible, however, to measure that amount of flexion. Hence, the low back and pelvis must be flat on the table. To get the low back and sacrum flat in a subject with hip flexor shortness, the hips must be flexed, but only by the amount necessary to obtain the desired position. (See facing page.)

HAMSTRING LENGTH: APPARENTLY NORMAL, ACTUALLY EXCESSIVE

The actual hamstring length is the same as that in the bottom figure on the facing page.

When hip joint flexion has reached the limit of hamstring length in the straight-leg raise, the hamstrings exert a downward pull on the ischium in the direction of posteriorly tilting the pelvis. To prevent excessive posterior pelvic tilt and excessive flexion of the back, stabilize the pelvis with the low back in the flat position, by holding the opposite leg firmly down. (If there is shortness of hip flexors and a roll or pillow must be put under the knees to get the back flat, then one leg must be held firmly down on the pillow to prevent excessive posterior tilt.)

APPARENT HAMSTRING LENGTH GREATER THAN ACTUAL LENGTH

Excessive posterior tilt of the pelvis allows the leg to be raised slightly higher here than shown in the figures above, even though the hamstring length is the same in both instances. With the opposite leg held firmly down, excessive posterior tilt will not occur except in subjects with excessive length in the hip flexors, which is not common.

EFFECT OF HIP FLEXOR SHORTNESS 387 ON HAMSTRING LENGTH TESTS

A test for length of hip flexors confirms shortness of these muscles. (See pp. 376-380 for hip flexor length tests.)

The hamstrings appear to be short. This test is not accurate, however, because the low back is not flat on the table. Shortness of the hip flexors on the side of the extended leg holds the back in hyperextension.

To accommodate for hip flexor shortness and allow the low back to flatten, the thigh is passively flexed by a pillow under the knee, not actively held in flexion by the subject. With the back flat, the test accurately shows the hamstrings to be normal in length.

In testing for hamstring length and in exercising to stretch short hamstrings, avoid placing one hip and knee in the flexed position (as illustrated) while raising the other. Otherwise, flexibility of the lower back is added to the range of hip flexion, making the hamstrings appear to be longer than they are. Not infrequently, a subject has excessive back flexibility along with hamstring shortness.

Flexion of the pelvis toward the thigh (i.e., hip flexion) appears to be normal in forward bending. Because both hips are in flexion in forward bending, hip flexor shortness does not interfere with movement of the pelvis toward the thigh, as occurs when one leg is extended in the supine position.

The lordosis in standing is evidence of the one joint hip flexor shortness in this subject.

ERROR IN TESTING

CORRECT TEST

When the straight-leg-raising test is done starting with one knee and hip flexed and the foot resting on the table as the other leg is raised, the pelvis is free to move in the direction of excessive posterior tilt, with the sacrum no longer flat on the table. Depending on the amount of flexibility of the back, the hamstring length will appear to be longer than actual, because back flexion is added to hip flexion. An individual with as little as 45° of actual hamstring length can appear to have as much as 90°, as seen in the photographs above.

NO STANDARDIZATION OF LOW BACK AND PELVIS

If the hip and knee are flexed to allow approximately 40° of hip flexion, the position will ensure enough slack in the hip flexors that they will not cause anterior pelvic tilt. This will not, however, insure against excessive posterior tilting. Standardization of the amount of hip and knee flexion will not standardize the position of the low back and pelvis, which must be standardized. Hip flexor shortness is the chief cause of anterior pelvic tilt in the supine position, and the degree of shortness varies from one individual to another. To stabilize the pelvis with the low back and sacrum flat on the table, one must "give in" to the tight hip flexors by using a pillow or towel roll under the knees, but only by as much as is necessary to obtain the required position of the pelvis.

THREE VARIABLES, NONE CONTROLLED

Sometimes an effort is made to determine hamstring length by ascertaining the number of degrees lacking in knee joint extension. The starting position is as follows: One leg is placed in approximately 40° of hip flexion, with the knee flexed and the foot resting on the table (giving rise to the problems cited above). The thigh of the opposite leg is raised to a position perpendicular to the table (which may—or may not—be 90° of true hip joint flexion). The knee is then moved in the direction of extension. The length of hamstrings is stated in the number of degrees the knee joint lacks in extension.

The following set of photographs demonstrate the need to pay strict attention to details in testing. During a hamstring length test, an error of omission on the part of the examiner can result in wrongfully labeling a subject as a malingerer.

1. Postural alignment: Pelvis sways forward, upper trunk goes backwards. Pelvis is in slight posterior tilt, putting endrange stretch on the iliop-soas, and allowing a shortened position of the hamstrings.

2 and 3. With the low back and one leg flat on the table, the other leg is passively raised to the extent allowed by the hamstring length. Each leg has been raised to an angle of 60°.

4. Actively, the subject raises the leg to an angle of 50° .The inability to complete the passive range of motion can result from slight stretch weakness of the iliopsoas. (See glossary for definition of stretch weakness.)

5. This photograph clearly illustrates excessive flexibility of the spine, especially of the lumbar spine.

6. The excessive flexibility of the lumbar spine permits excessive posterior pelvic tilt. This position of the pelvis puts the hamstrings on a slack over the hip joint, and enables the subject to reach forward with knees fu\\y extended to touch his toes, in spite of hamstring shortness.

7. When the hamstrings are allowed to be slack over the hip joint by the excessive posterior pelvic tilt, the knee can be fuily extended in sitting.

8. With the low back and pelvis held in good alignment, the shortness of the hamstrings is evident by the lack of the knee extension.

390 HAMSTRING STRETCHING

STRAIGHT-LEG RAISING

As illustrated by the figure below, hamstring stretching may be performed as a passive exercise or as an active, assisted exercise. It may be performed as an active exercise if not contraindicated because of tightness of the hip flexors.

To stretch the right hamstring, lie on the table with the legs extended, and have an assistant hold the left leg down and gradually raise the right leg with the knee straight (or strap the left leg down and raise the right leg actively). To stretch the left hamstring, apply the same procedure to the left leg.

The exercise also may be performed by putting the leg in a position that places a stretch on hamstrings, such as supine on the floor, with one leg extended, the other leg raised, and the heel resting on the back of a chair, or lying in an open doorway area, with one leg extended and the other raised and the heel resting against the wall. To increase the stretch, move the body closer to the chair or wall. Avoid placing both legs in the raised position at the same time, because the low back will be stretched instead of the hamstrings. Keeping one leg extended prevents excessive posterior tilt of the pelvis and excessive low back flexion. (See exercise sheet pp. 462, 463.)

KNEE EXTENSION IN SITTING POSITION

Sit with the back against a wall, as illustrated by the figure below. With the back kept straight and the buttocks touching the wall, raise one leg, extending the knee as much as possible.

POSITIONS TO AVOID

Avoid the standing position, with one heel on a stool or table and forward bending. For patients with pain or disability, this is a risky position. It also makes it impossible to control the pelvic position to insure proper hamstring stretching. Furthermore, the exercise has an adverse effect on anyone with a kyphosis of the upper back. Exercise should be localized to stretching the hamstrings.

Avoid the "hurdler's position" for stretching the hamstrings. Excessive strain is placed on the bent knee, and the low back is excessively stretched.

AVOID

Avoid forward bending to stretch the hamstrings in cases with excessive flexion of the back, as seen in the figure below.

| HISTORICAL NOTE ABOUT THE OBER TEST

In the Journal of the American Medical Association, May 4, 1935, there appeared an article by Frank Ober of Boston entitled "Back Strain and Sciatica" (4). In it. he discussed the relationship of a contracted tensor ! fasciae latae and iliotibial band to low back and sciatic pain. The test for tightness was described, but Ober did not mention anything about avoiding hip flexion or in-| ternal rotation as the thigh is allowed to drop in ad-i ductioii.

After the article appeared, Henry O. Kendall,* then a physical therapist at Children's Hospital School in Baltimore, expressed concern about the test to his medical director, George E. Bennett. The concern was that allowing the thigh to drop in flexion and internal rotai tion would "give in" to the tight tensor and not accurately test it for length. At some point in late 1935 or early 1936, Dr. Ober visited Children's Hospital School, and Mr. Kendall expressed concern about the test to him personally.

In the Journal of the American Medical Association, August 21, 1937, another article appeared in which Dr. Ober again described his test but, this time, he cautioned the examiner to avoid hip flexion and internal rotation as the thigh is allowed to adduct (5).

Apparently, some people who have described the I test had access to the first article but not to the second. A well-known text describes positioning the leg in abduction, with the hip in a neutral position and the knee flexed 90°, and then releasing the abducted leg (6). The text also states that the normal iliotibial band will allow the thigh to drop to the adducted position (as illustrated by the knee touching the other leg or the table). A tensor fasciae lata of normal length will not permit the thigh to drop to table level unless the hip goes into some internal rotation and flexion.

In the first article, Ober stated, "The thigh is abducted and extended in the coronal plane of the body." With respect to what should be considered a "normal" range of motion in the direction of adduction, this article stated, "If there is no contraction present, the thigh will adduct beyond the median line." It must be noted that this statement referred to the test in which no reference was made about preventing flexion and internal rotation.

In the second article, Ober did not specifically refer to the coronal plane, but he did state, "The thigh is allowed to drop toward the table in this plane." By the description, Ober was referring to the coronal plane. Maintaining the thigh in the coronal plane prevents hip joint flexion.

The second article made no mention of how far the thigh should drop toward the table. (See below for further discussion about normal range of motion in adduction.)

Before deciding what may be considered a normal range of adduction in the Ober test, it is necessary to review normal range of motion of the hip joint. Contrary to the information in several books (7-11), the normal range of hip joint adduction from the anatomical position (i.e., in the coronal plane) is—and should be—limited* to approximately 10°.

If adduction is limited to 10°, then in the side-lying position, with the pelvis in a neutral position, the extended extremity should not drop more than 10° below the horizontal if kept in the coronal plane. In flexion and internal rotation, the range in adduction is greater, but such a position is no longer a test for length of the tensor fasciae latae. The action of the muscle is abduction, flexion, and internal rotation of the hip as well as assisting in extension of the knee. By "giving in" to flexion and internal rotation, the muscle is not being lengthened.

Limitation of range of motion provides stability by preventing excessive motion. Limitation of knee-joint extension prevents hyperextension. Limitation of hip joint extension prevents the pelvis from swaying forward abnormally in standing. Limitation of hip joint adduction provides stability for standing on one leg at a time.

In the 1937 article, Ober also stated that "when the maximum amount of fascial contracture is on the side and in front of the femur, the spine is held in lordosis, and that if the contracture is posterolateral, the lumbar curve is flattened. The former condition is common; the latter is rare. Either condition may be associated with pain low in the back and sciatica. Unilateral contracture may produce lateral curvature of the spine"

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Responses

  • mari nykänen
    What is a normal straight leg test for hamstring length?
    1 year ago

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