Sensory input informs motor output

Proprioception is generated by receptors within ligament, capsular, and musculotendinous tissues throughout the body, including the anterior cruciate ligament (ACL).

As we know, these signals allow perception of body positions, movements, and muscular effort. Integration of this diverse and distributed array of somatosensory afference is incredibly complex, including spinal cord, cerebellar, and higher-order centers.

Vision is another sensory signal generated by receptors in the eyes. When performing a task (e.g., climb stairs, pouring a drink, etc.), would you do it differently without vision?

The ACL and surrounding knee joint structures constitute the largest sensory organ in the human body. Loss of input stemming from an ACL tear, is essentially being “knee blind”. Pain and swelling in the joint further serve to alter sensory inputs.

When performing a task (e.g., walking, squatting, kicking), would you do it differently without knee proprioception?

The status of this “sensory deprivation” clearly has functional and clinical implications up the (sensorimotor) chain but is largely unknown or unmeasured after ACL injury and reconstruction.

Clinical Bottom Line: Train it in rehabilitation. Rehabilitation and physical therapy should leverage principles of motor learning. Motor skill development helps our clients overcome isolated limitations in proprioception through upregulation of intact systems.