EXERCISE IN ORTHOPEDIC DISORDERS

Rehabilitation after an acute injury, surgery, immobilization, or chronic orthopedic condition must address all the components of normal function. Regaining lost strength, reducing pain and swelling, improving flexibility, enhancing local muscular endurance, and building cardiovascular fitness are obvious and vital areas requiring specific therapeutic interventions. Sometimes less apparent, but equally important, is the need to address the motor control and neuromuscular elements to promote synchronous, fluid, and stable motor function of the injured part within the context of the distal and proximal body parts. Furthermore, secondary to the interdependence of coordination, posture, and balance to gait and functional movements, attention must also be placed on these elements for complete recovery from injury. Long-term convalescence reduces strength, flexibility, and cardiorespiratory fitness, as well as the use of vestibular and afferent neural input needed for balance and coordination.

DEFINITIONS OF BALANCE, PROPRIOCEPTION, NEUROMUSCULAR CONTROL, AND COORDINATION

Balance is often considered as the ability to maintain the center of mass (COM) over the base of support.¹² This definition is only appropriate, however, when the base of support is fixed, such as standing in a constant location on two feet. The base of support is defined as the area contained within the parts of the body making physical contact with the external environment (Fig. 6-1).⁹ During dynamic situations, such as gait and functional activity, the base of support does not remain fixed to a constant location. Rather, as part of locomotion, the base of support moves, increasing the challenge to the elements responsible for maintaining balance. For this reason, the concept of balance also needs to include consideration to these circumstances. Postural equilibrium is a broader term that refers to balancing all forces acting on the body’s COM to maintain COM within the limits of stability with optimal joint segment alignment.¹ Forces that challenge postural equilibrium arise from gravity, unexpected perturbations (i.e., stumbling over an unforeseen obstacle), or performance of voluntary motor activities (i.e., picking up a bag of groceries). Maintaining postural equilibrium is accomplished by the postural control system, the collection of sensory sources (somatosensory, vision, and vestibular), central nervous system, and the musculoskeletal system, all serving to maintain postural equilibrium. The somatosensory sources relevant to postural equilibrium are the mechanoreceptor populations residing in joint, muscle, connective, and ligamentous tissues. Because these tissues are often damaged during orthopedic injury, postural equilibrium may be disturbed following injury because of sensory disruptions, musculoskeletal disruptions, or both.⁹

Performing motor tasks effectively and efficiently requires not only postural equilibrium, but also effective coordination of the many muscles serving to move and stabilize the joints upon which they cross. Coordination has been defined as the ability to produce patterns of body and limb motions in the context of environmental objects and events.¹³ For example, picking up an object from a table requires coordinating the shoulder, elbow, and wrists joints to put the hand and fingers into position so the object can be grasped. Essential to coordinating joint positions is sufficient sensory (afferent) information regarding joint position, movement (kinesthesia), and movement resistance/tension. The afferent information contributing to these three elements, joint position, movement (kinesthesia), and movement resistance/tension, is referred to as proprioception.¹² When the proprioception elements are consciously perceived, they are referred to as the conscious perceptions of proprioception.¹² Proprioception is vital for neuromuscular control. From a joint stability perspective, neuromuscular control refers to the subconscious activation of muscles occurring in preparation for and in response to joint motion and loading.¹²

BALANCE AND COORDINATION TESTS

To prescribe appropriate balance and coordination exercises, it is essential to have data related to present balance and coordination status. Most often, coordination is evaluated by using the simple tests such as those outlined in Box 6-1. Although quantifying a patient’s coordination abilities can be easily accomplished by counting the number of repetitions completed in a given time frame or the number or percentage of successes per number of attempts, qualitatively examining and describing the patient’s abilities and difficulties (e.g., steadiness, control, speed) can also be useful.

Interestingly, balance tests and specific balance treatment activities are rarely separated, and the same movements are used for fundamental balance exercises and clinically relevant balance tests. Recall that three sensory sources, somatosensory, visual, and vestibular, contribute afferent information to the central nervous system so that appropriate muscle actions can be selected. By manipulating the conditions in which balance tasks are conducted, different aspects of the postural control system may be more selectively challenged.⁹ For example, having a patient stand with eyes closed heightens their reliance on somatosensory and vestibular information. In addition, manipulating the base of support and support surface characteristics can also change the challenge imposed upon the postural control system. For example, compared to double-leg stance, single-leg stance requires that the postural control system reorganize itself over a narrow and short base of support, with the additional advantage that bilateral comparisons can be made. Functionally, periods of single-leg stance are often interspersed in many activities of daily living, such as walking, turning, climbing stairs, and putting on a pair of pants. Further, during activities of daily living, one does not usually solely concentrate on maintaining balance, but rather on the details of the task (e.g., reaching up to remove the correct book from a shelf). Additionally, during activities of daily living, situations arise where unexpected challenges (perturbations) to postural equilibrium occur. Thus comprehensive balance assessment and training frequently call for a progressive battery of specific tasks of incremental difficulty and should include not only static stances with varying bases of support and support surface characteristics, but also tasks that involve voluntary movement and task completion and unexpected perturbations.⁹ Close observation of the patient’s protective reactions during loss of balance is a critical component of all balance tests and training activities. Immediate corrective action by the patient to maintain balance is necessary to move the patient from low-level balance activities to more challenging, complex maneuvers.