In contrast, the thoracic facet joints are oriented more obliquely, so thoracic movement is more equal among the three planes. Thoracic sidebending is relatively limited (Smith, Weiss, & Lehmkuhl, 1996, Fig. 11-3, p. 373), not because of the facet joints' orientation but because of the presence of the ribcage.
Stand and, placing your your hands on your partner's right and left shoulders, assess their relative height.
If you find that the pelvis is not level, investigate the source of the asymmetry.
The measurement technique is described in:
Scoliosis can be structural or functional. If it is functional, the scoliosis (and its signature rib hump) should disappear when the pelvis is level. To find out if the scoliosis is functional, repeat the forward bending test with your patient seated on a hard surface. If the rib hump persists, the scoliosis may be structural, that is, related to asymmetries or abnormalities in the spine's bony structure.
You can relate your partner's posture to the figures in Muscles: Testing and Function that begin on page 84. However, we don't fully understand the reliability of this system for naming postures.
Identify trunk and hip muscles whose activity tilts the pelvis anteriorly or posteriorly, and thereby alters the lumbar spine's posture in the sagittal plane.
posterior pelvic tilt: a sagittal plane motion that causes the ASIS to move posteriorly. | ![]() |
---|
Use a pen to mark the midpoint between the posterior superior iliac spines (PSIS). Then use your tape measure to identify and mark two points: (1) one that is 10 cm superior to the PSIS, and (2) one that is 5 cm inferior to the PSIS.
As your partner flexes the spine as far as possible, measure and record the distance between the superior and inferior marks.
Similarly, measure and record the distance between the superior and inferior marks as your partner extends the spine as far as possible.
Lab partner | Distance (in cm) during flexion | Distance (in cm) during extension |
---|---|---|
1 | ||
2 | ||
3 | ||
4 |
This modification of the Schober test is published in:
Moll, J.M., & Wright, V. (1971). Normal range of spinal mobility: An objective clinical study. Annals of the Rheumatic Diseases, 30, 381-386.
As your lab partner stands barefoot on one leg (with the eyes closed), observe and palpate the tendons of the extrinsic foot muscles, which cross both the ankle and subtalar joints. As the person "sways" over the base of support, and the line of application of gravity moves anteriorly or posteriorly, medially or laterally, how does it affect the ankle and subtalar joints. Which muscles activate to counter gravity's effects on the two joints?
After you've considered this problem, you can consult a commentary that addresses it.
Gravity's line of application (also called the "gravity line") proceeds vertically from the body's center of gravity into the floor. If you maintained your balance on one foot, you know that the line always passed into your one-footed base of support. Even so, the line moved back and forth as your body swayed. When, for example, gravity's line of application moves anteriorly with respect to the ankle's axis, it produces a dorsiflexion moment at ankle, and necessitates activity in the plantar flexors. Conversely, when gravity's line of application moves posteriorly to the ankle's lateral axis, gravity's force plantar flexes the ankle. In response, dorsiflexors activate, and may lift the toes from the floor.
Your body sways anteriorly and posteriorly, and simultaneously sways from side to side. Therefore, gravity's line of application migrates not just anteriorly or posteriorly, but medially or as well. The medial-lateral movement causes gravity's line of application to cross to either side of the subtalar joint's axis. Because standing is a closed chain activity, the calcaneus is relatively stable and the talus and lower leg are relatively mobile. The frontal plane figure depicts the stable calcaneus in green. | ![]() |
---|---|
When gravity's line of application is lateral to the subtalar axis, it produces a pronation moment at the subtalar joint. The calcaneus and foot are relatively stable, while the talus, tibia, and the rest of the body incline laterally. Note that the calcaneus is everted in relation to the long axis of the lower limb, indicating that the subtalar joint pronates in a closed chain. | ![]() |
Muscles whose lines of application pass on the subtalar joint's medial side, and which therefore supinate the subtalar joint, activate to realign the tibia and the body over the stable base of support. These muscles' activity may elevate the foot's medial side. | ![]() |
When gravity's line of application is medial to the subtalar joint's axis, gravity produces subtalar supination. The foot remains relatively stable while the talus, tibia, and the rest of the body incline medially. Note that the calcaneus is inverted in relation to the long axis of the lower limb, indicating that the subtalar joint supinates in a closed chain. | ![]() |
Muscles whose lines of application pass on the subtalar joint's lateral side, and which therefore pronate the subtalar joint, activate to realign the tibia and the body over the stable base of support. These muscles' activity may elevate the foot's lateral side. | ![]() |