The fitness, sports performance, and rehabilitation industries often describe movement within the body as a series of alternating joint levels of mobility-stability-mobility patterns. While I agree with the idea of trying to provide a systematized arrangement of movement, the description implies that motion is one-dimensional, when, in reality, every muscle and every joint works in three planes of motion. In fact, there must be adequate range of motion in all three planes to allow efficient, economical, and successful chain reaction of synchronized movement.
This article is divided into two sections. Part 1 discusses the principles and concepts of movement, expression of relative motion of joints, and basic foot mechanics, then delves into the lower extremity, knee, and hip. Part 2 will explore will the complexity of the lumbar and thoracic spine and the shoulder girdle.
Let’s establish a concept that sets the premise for the larger discussion. Movement can be described as the relationship of bone segments that comprise the joints.
When discussing motion of the extremities, we must look at the position of the distal bone in relation to the proximal bone. For example, in Figure 1.1 we see the open chain position of hip adduction with the femur medial to the ilium. In Figure 1.2, we also see the closed chain, integrated position of hip adduction even though the foot is not moving in space as in the open chain action. In both pictures, the femur (the distal bone) is medial or adducted to the ilium (the proximal bone).
|In both photos above, the distal segment (femur) is medial to the proximal segment (ilium).
In the spine, however, movement is the proximal bone in relation to the distal bone. In Figure 2.1, we see rotation of the cervical spine to the left with the chin somewhat over the left shoulder. The proximal segments of the cervical spine are rotated left further than the distal cervical segmental levels. When viewing the integrated action as shown in Figure 2.2, there is still left cervical rotation even though the body is rotated right; the proximal cervical segments are left of the distal segments.
|In Figure 2.2, the lower segment of the cervical spine and thoracic spine are rotated right. However, the proximal segments are relative left to the distal segments. Therefore, this is still left cervical rotation.
Our discussion will begin at the foot, move through the subtalar joint, and proceed up the chain to the cervical spine.
One of the most fascinating and complex structures in the body is the foot (see Figure 3), yet it is mostly overlooked by the fitness industry. Comprised of 24 muscles, 26 bones, and 33 joints, the foot is the conduit that interfaces with the ground and creates a platform for the body to react. The foot is categorized into three regions: the forefoot, mid-foot, and rearfoot.
The forefoot consists of the toes (phalanges) and long bones (metatarsals). The great toe has two bones, one joint, and metatarsals, while each of the other four phalanges has three bones and two joints.
The mid-foot includes the three cuneiforms (medial, intermediate, and lateral), the navicular on the medial column, and the cuboid on the lateral column. These five bones form the mid-foot arch and must be mobile to absorb forces during the “collapse” of the arch during pronation.
The calcaneus (heel) and talus make up the rearfoot. The calcaneus has a concave surface on the superior aspect and the talus is convex at the inferior surface. The union of the calcaneus and talus form the subtalar joint, an extremely important joint that sets the environment for successful tri-plane motion.
When describing the action of the rearfoot, I often use the analogy of a bicyclist riding a bike (see Figure 4). Imagine a cyclist riding along and starting to lose balance. The bike falls to the right while the tires turn outward to the left. In our analogy, the tires and bike are the calcaneus, while the cyclist is the talus. The “cyclist”/talus wears a long helmet called the tibia; in other words, the tibia sits atop the talus. As the bike falls to the right, the tires turn outward, similar to the left foot hitting the ground and causing the calcaneus to evert (heel “falls” right, while the bottom of the heel turns outward). With the foot on the ground during the landing phase of gait, the medial column of the foot — composed of the union of the talus and navicular forming the talo-navicular joint — fall medially toward the ground. Based upon the axis of motion, the talo-navicular and subtalar joints’ primary motions are eversion-inversion in the frontal plane. This motion allows the tibia to move further forward in the sagittal plane and dorsiflex at the ankle, while also internally rotating in the transverse plane.
Most texts discuss the sagittal plane of the ankle because in a strictly isolated sense, the talocrural joint (ankle) is strictly a sagittal plane mover. However, when the foot loads upon hitting the ground the ankle dorsiflexes in the sagittal plane, the calcaneus everts, causing the subtalar joint to evert in the frontal plane, and the tibia internally rotates in the transverse plane. This reaction then causes the mid-foot to evert in the frontal plane. The forefoot abducts in relation to the mid- and rearfoot due to the description of motion as the distal bone in relation to the proximal bone segments. Because the rearfoot and mid-foot move further and faster in the frontal plane than the forefoot, the metatarsals and phalanges are lateral to the proximal segments, therefore, are abducted to the rearfoot.
As a review, when the foot hits the ground in the pronation phase, the lower extremity is eccentrically loaded by virtue of:
- Calcaneal eversion
- Ankle dorsiflexion
- Tibial internal rotation
- Forefoot abduction
These motions clearly show the foot and ankle complex is moving in three planes of motion. It is commonly agreed that we want mobility in the foot during the pronation phase, which allows absorption of forces. Yet, as ambulation takes place and the hip moves over the foot, the opposing swing leg will drive the opposing hip forward, which will invert the calcaneus, plantar flex the ankle, externally rotate the tibia, and adduct the forefoot of the stance leg (see Figure 5).
Figure 5. In this photo sequence, notice the left leg and foot. The left leg is relatively externally rotated with the foot inverted. As the foot hits the ground, the foot pronates, which enhances relative dorsiflexion, tibial internal rotation, and forefoot abduction. As the hip moves over the foot, the heel rises off the ground, foot inverts and “locks” up the mid-foot, enabling the foot to be a cantilever to propel relative ankle plantar flexion, extension for the metatarsals, forefoot adduction, tibial external rotation, and hip extension.
In motion, the ankle joint moves primarily in the sagittal plane. However, it needs some degree of frontal plane action, though not to the point that it creates too much mobility and increases risk of ankle injuries. This is very important, as the foot and ankle must undergo these actions to create an environment for successful knee and hip function.
Books describe knee motion primarily in the sagittal plane as it flexes and extends. Health and sports performance professionals frequently preach that the knee must be stable in side-to-side or frontal plane motion. Rarely, however, do we preach that the knee must move in the frontal and transverse planes when the knee flexes and decelerates movement. For years, numerous articles have been written stating the knee must track over the 2nd and 3rd metatarsals when doing a lunge or a squat. If this is the case, then why does nearly every athletic movement requiring deceleration and change of direction cause the knee to move medially to the foot and hip as shown in Figure 6? Notice how the hitter’s left knee is medial to the left foot. This allows the hip to eccentrically load as he drives off his left foot in preparation to run.
As the foot moves through pronation (calcaneal eversion, dorsiflexion, tibial internal rotation, and forefoot abduction), the tibia internally rotates on the talus. For example, perform a lunge and place your hand on your tibial line as you do the lunge. If you are doing a successful lunge, notice the calcaneus everting, the ankle dorsiflexing, and the tibia turning inward as the knee flexes. Using the concepts of movement, the tibia is internally rotated to the femur; therefore, in relation to the proximal bone (femur), the distal bone (tibia) will place the knee into internal rotation in the transverse plane. Likewise, if we view the distal end of the tibia in relation to the distal end of the femur, you will notice the tibia is lateral to the femur. Therefore, is described as abducted in the frontal plane. This often can be confusing because people see the knee toward the mid-line and say the knee is adducted, but by the principles of movement, the distal bone is abducted to the proximal bone, thereby putting the knee into knee abduction.
I often have said that the knee is the dumbest joint in the body because it is highly influenced by the foot motion and position, as well as that of the hip. Consequently, I am not overly concerned that the knee may move medially to the foot. HOWEVER, I am very concerned of WHY the knee may move and react the way it does. If a client does a lunge or a squat and they cannot return to the starting position without a smooth transition, then I want to know why. We must look at foot function as well as hip function to make the knee successful.
To review, the knee should be fairly mobile in the sagittal plane, but also must have some degree of transverse plane and frontal plane mobility. We must raise a cautionary eye to how smooth, efficient, and successful the transition is from loading the knee, and how much control is demonstrated when moving through the frontal plane and returning to the start position. If the movement is looking uncontrolled and sloppy, then we must do strengthening and corrective exercise to stabilize that action. But never should there be such stability at the knee that no frontal or transverse plane motion occurs.
The actions that promote successful knee function are:
- Knee flexion in the sagittal plane.
- Knee abduction in the frontal plane by the tibia being abducted (lateral) to the femur.
- Knee internal rotation as a resulting tibial internal rotation of the tibia in relation to the femur.
One of the most mobile regions of the body is the hip complex; the other is the thoracic spine. A myriad of dysfunctions can develop when the hip is immobile in one or more planes of motion. Among them are knee pain, sacroiliac pain, low back pain, and even shoulder discomfort.
Starting from the foot reaction, we learned that as the foot pronates the calcaneus everts, the ankle dorsiflexes, the tibia internally rotates, and the forefoot abducts. As the tibia internally rotates, the knee flexes in the sagittal plane, abducts in the frontal plane, and internally rotates in the transverse plane. As the femur reacts to the other motions below it, the forward motion of the femur will result in hip flexion in the sagittal plane. Simultaneously, as the knee abducts, the femur is “pulled” medially causing hip adduction because the distal bone (femur) is now medial to the proximal bone (ilium). The alignment of the femur in relation to the ilium and knee cause the femur to internally rotate in relation to the ilium when loading the hip. Considering the gluteal complex, especially the gluteus maximus, is attached at the greater trochanter, gluteal line, and posterior superior iliac spine, the gluteal tissue is eccentrically loaded as the hip flexes, adducts, and internally rotates. In Figure 7, notice the relationship of the bone segments to load the hip in all three planes of motion during this frontal plane lunge with opposite lateral reach.
During the gait cycle, all the above actions occur on the weight-bearing side as a person moves forward. We must also pay attention to the motions of the non-weight bearing side as the leg swings through to the next step. For consistency, let’s consider the above description on the left side and the right leg is about to swing through during the gait cycle. In Figure 8, the pelvis is rotated to the right just prior to the right heel lifting off the ground. As the heel lifts off the ground, the pelvis starts to rotate left, creating a relative externally rotated right hip, as the ilium is rotated left further than the femur. Or, to say it another way, the femur is rotated right (externally rotated) to the ilium in the transverse plane. As the right leg begins to swing forward, the right hip is lower than the left and slightly medial to the right leg. Therefore, since the right leg is lateral to the ilium, the right hip is abducted during this swing phase. Additionally, the leg is extended to the hip. Hence, the hip is extended in the sagittal plane. All these actions are critical for shock absorption, force production, and force transmission during the efficient and economical gait cycle. As importantly, however, these actions are critical in reducing overuse issues, especially in commonly injured areas such as the lumbar spine.
To review, the weight-bearing hip will move in three planes of motion and undergo loading or deceleration during the following actions for successful movement:
- Hip flexion in the sagittal plane
- Hip adduction in the frontal plane
- Hip Internal rotation in the transverse plane
The extended, non-weight bearing hip at heel off is:
- Hip extended in the sagittal pla
- Hip abducted in the frontal plane
- Hip externally rotated in the transverse plane
Part 2 of our Three Dimensional Joint-by-Joint Approach to Movement will look into the three dimensional motions of the lumbar, thoracic, and cervical spine, and shoulder girdle. Also, you will be able to discover the impact of adjacent joint motions upon other regions of the body. When we are able grasp these principles and concepts, it will allow us to view clients’ movements from a different perspective and to appreciate the “why” of “how” they move.
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