Flexion

Flexion: A sagittal plane joint action that results in a decrease in angle between two bones.

• Opposing Joint Action: Extension
• Plane of Motion: Sagittal
• Direction Bias: Foward
• Note: Joint actions may be referred to as "osteokinematic motions" or "osteokinematic joint actions" to differentiate them from "arthrokinematic motions " (e.g., spin, glide, roll, compression, and distraction).

For more (including a video lecture), check out:

• Lesson 3: Joint Actions
• Lesson 18: The Spine and Trunk Muscles

Joints that Perform Flexion (and Sample Exercises):

1. Shoulder joint (Glenohumeral joint): Flexion involves raising the arm forward and upward, as observed during a shoulder front raise or close-grip push-up .
2. Elbow joint: Flexion involves bending the elbow, bringing the forearm toward the upper arm, as observed during a bicep curl or row .
3. Wrist joint: Flexion occurs when the hand moves forward in the direction of the palm side of the hand, as in wrist flexor activation exercises .
4. Hip joint : Flexion is bringing the thigh forward and upward, as observed during psoas activation exercises .
5. Knee joint : Flexion involves bending the knee, bringing the lower leg back toward the thigh, as observed during leg curls.
6. Ankle joint (Talocrural joint) : Dorsiflexion is a specific form of flexion at the ankle, where the foot moves up toward the shin, as observed during tibialis anterior activation .
7. Interphalangeal joints (fingers and toes): Flexion occurs when the fingers or toes curl inward toward the palm or sole, as observed when gripping an object in the hands.
8. Spine (Intervertebral joints) : Flexion occurs when the spine bends forward, as observed when performing a crunch .