Functional anatomy, movement and localization
Functional anatomy connects a structure to an observed task rather than asking the learner to memorize isolated names. A muscle produces a moment according to its force and perpendicular distance from the joint axis. The same muscle can act differently when the limb position, external load or fixed segment changes. Identify whether the task involves open or closed chain movement and whether the contraction shortens, lengthens or maintains muscle length. An eccentric contraction resists lengthening; it is not the absence of muscular effort.
Peripheral nerve patterns should be compared with root and central findings. A radial nerve lesion can impair wrist and finger extension, while an ulnar lesion can affect intrinsic hand function. Sensory territories and reflexes help refine localization, but overlap and individual variation limit conclusions from a single point. A dermatome map is not proof that a peripheral nerve problem has been excluded. Use the whole history, distribution, strength pattern and appropriate qualified assessment.
Joint movement combines rolling, sliding, rotation and changing tissue constraints. Common teaching ratios, such as scapular contribution during arm elevation, are approximate models rather than fixed relationships throughout every degree. Pelvic drop during single-leg stance can suggest insufficient stance-side hip-abductor control, but pain, balance strategy and neurological factors may contribute. Avoid equating every observed movement deviation with one isolated weak muscle.
Motor control requires coordination between descending pathways, sensory feedback, anticipatory activity and the task environment. Upper motor neuron patterns may include hyperreflexia, spasticity and an extensor plantar response in an adult. Lower motor neuron involvement can produce weakness, reduced reflexes, atrophy and denervation findings. Timing and combined lesions can complicate the picture, particularly immediately after spinal cord injury.
Use diagrams and functional examples to consolidate the relationships. For a patient who cannot clear the toes in swing, compare ankle dorsiflexion strength, selective control, tone, sensation, footwear and the device in use. Do not prescribe an orthosis from the diagnostic label alone. Record which findings were actually observed and which mechanism remains a hypothesis. Anatomy supports reasoning, but new progressive weakness or another serious neurological change requires prompt clinical escalation rather than an extended exercise trial.