10.1 Types of Joint Movement

Biomechanics is the study of how forces and geometry show up in living bodies. Yoga Alliance lists types of joint movement as a Biomechanics sub-competency in the Anatomy and Physiology category of the RYS 200 common core (Standards for RYS Credentials, May 2025). This OpenExamPrep section teaches those movement names so you can see what a pose is actually doing, cue with precision, and stop treating every sensation as “tight hamstrings.” Independent study here does not replace a single 200-hour RYS program, and OpenExamPrep does not present this guide as a Yoga Alliance product.

Planes of Motion

Describe motion relative to three imaginary planes that cut the body in anatomical position (standing, palms forward). A movement lives in a plane when the moving bone travels roughly parallel to that plane. The axis of rotation is perpendicular to the plane: sagittal motion spins around a roughly medial–lateral axis, frontal motion around an anterior–posterior axis, and transverse motion around a vertical axis.

Most asanas combine planes. Warrior II is not “one plane”: the lead hip is more abducted in the frontal plane while the spine stays relatively upright and the neck may rotate in the transverse plane to look over the front hand. Naming the dominant action still helps you choose a regression (less abduction, a shorter stance) instead of a random extra stretch.

Flexion, Extension, and Hyperextension

Flexion decreases the angle between two segments on the side of the body that is anterior in anatomical position, with exceptions you must memorize for teaching. At the knee and the toes, flexion is posterior (heel toward the seat; toes curling). At the shoulder, sagittal flexion lifts the arm forward toward overhead; at the hip, flexion folds the thigh toward the belly, as in a high lunge or Navasana (Boat). Elbow flexion is the Chaturanga bend; wrist flexion is the “break” some students show when they dump into the heels of the hands.

Extension returns a flexed joint toward anatomical position and, at the hip and shoulder, can continue slightly behind the frontal midline of the trunk. Setu Bandhasana (Bridge) is hip extension plus spinal extension. Virabhadrasana I asks the back hip for extension while the front hip stays flexed—two different stories in one stance. Spinal extension is the lengthening-backbend family; it is not automatically “opening the heart,” which is poetic language, not a joint action.

Hyperextension is extension that travels past the joint’s typical anatomical position. Elbows that lock backward in Adho Mukha Svanasana, knees that snap back in Tadasana, and cervical crunches that throw the skull behind the shoulders in a cobra variation are classroom hyperextension patterns. Hyperextension is a description of position, not a moral failure and not automatically an injury. Some bodies have more bony or ligamentous allowance. The teaching job is to notice whether the student is dumping load into a taut capsule instead of sharing work through muscle. A micro-bend in a hyperextended elbow or knee is a stability strategy, not a punishment.

Abduction, Adduction, Circumduction, and Rotation

Abduction moves a limb away from the midline. Shoulder abduction raises the arms toward a T, as in Virabhadrasana II. Hip abduction takes the thigh out to the side, as in a standing wide stance or a supported side-lying leg lift. Finger abduction spreads the fingers on the mat, a small but useful cue for wrist comfort.

Adduction returns the limb toward or across midline. Crossing one thigh over the other in a seated twist is hip adduction (often mixed with rotation). In Chaturanga Dandasana, hugging the upper arms toward the ribs is a form of humeral adduction combined with elbow flexion.

Circumduction is a sequential combination of flexion, abduction, extension, and adduction so the distal end of the limb traces a cone. Shoulder circles in a warm-up are circumduction. Circumduction is not a sixth primary plane; it is a composite path. If a student has pain in one sector of the circle, shrink the cone rather than speeding up. Do not call a simple head turn “circumduction.”

Rotation turns a bone around its long axis. Internal (medial) rotation of the humerus points the inner elbow more forward; external (lateral) rotation points it more out. The hip uses the same language: Warrior II generally wants a more externally rotated front thigh so the knee tracks with the second toe, whereas a lunge with a parallel pelvis uses less external rotation and more sagittal flexion. Spinal rotation is named right or left (the direction the chest or nose turns—say which landmark you mean). Circumduction is not a substitute word for rotation; rotation can occur without a conical sweep, as in a simple cervical turn to look toward the front hand.

Ankle and Foot: Dorsiflexion, Plantarflexion, Inversion, Eversion

The talocrural (true ankle) joint is primarily a hinge in the sagittal plane:

• Dorsiflexion brings the dorsum of the foot toward the shin (toes toward the knee). It is the lifted-toes action in Tadasana and the shin-over-ankle goal in many lunges.
• Plantarflexion points the foot, as in a linger at the back of a kick or the back foot’s tendency in a high lunge if the heel lifts.

The subtalar and related foot joints supply frontal-plane vocabulary:

• Inversion turns the sole toward midline (rolling onto the outer edge). Many students invert the front foot in Triangle or the standing foot in Vrksasana (Tree), shrinking the base of support.
• Eversion turns the sole outward. A collapsed inner arch that rolls the ankle in is a common eversion-adjacent pattern. Do not diagnose “overpronation” as a disease—describe what you see and offer a shorter stance, a wedge, or less depth.

Name the joint and the action when you cue: “dorsiflex the front ankle” is clearer than “flex your foot,” which students hear as toe-curling.

Teaching List: Translate Sensation into Actions

Use this checklist when a student is “stuck”:

1. Name the joint (hip, knee, glenohumeral, talocrural, spine).
2. Name the plane (sagittal, frontal, transverse).
3. Name the action (flexion, abduction, external rotation, dorsiflexion, and so on).
4. Decide whether you want more range, less range, or the same range with more control.
5. Change one variable: stance width, knee bend, block height, or the amount of rotation.
6. Watch the neighboring joint. Extra lumbar extension often appears when hip extension is limited; extra knee rotation appears when the hip will not rotate.
7. Keep hyperextension on your radar at elbows, knees, and the cervical spine.
8. Treat circumduction as a warm-up option, not as a test of “full circles at all costs.”

If you can say, in one breath, “this is frontal-plane hip abduction plus sagittal-plane knee flexion,” you are doing 200-hour biomechanics, not reciting trivia. School written tests and teaching observations both reward that translation from shape to joint action.