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Causes of impaired motion in patients with musculoskeletal conditions

This is an excerpt from Therapeutic Interventions for Musculoskeletal Conditions With HKPropel Online Video by Craig R. Denegar,Grant Norte,Neal Glaviano.

Impaired motion can result from neuromuscular or mechanical sources. Functional movements of articulating joint surfaces involve rolling, spinning, and gliding of the joint surfaces. These motions, called arthrokinematics, allow an individual to move their joints through the planes of motion (flexion, abduction, internal rotation), which are termed osteokinematics. Pain-induced muscle spasm and poor stretch tolerance limit motion as a result of alterations in neurofeedback loops regulating the length of muscle fibers. Alterations in arthrokinematics, swelling, the presence of loose pieces of tissue in a joint, and shortening of connective tissues (e.g., ligament, joint capsules, muscle tendon units) affect the mechanical function of a joint, thereby limiting the osteokinematic or primary motion.

Neuromuscular Contributions

A pain–spasm cycle is common following injury and the onset of acute pain. The loss of motion and function associated with these events can protect injured tissue and limit spikes in pain. Increases in muscle tension can persist long after a precipitating event or emerge gradually as a result of prolonged postural positions or a response to stress. The affected muscles are maintained in a heightened state of sensitivity by increased gamma motor neuron activity, which increases tension within the residing muscle spindles. Normally tolerated increases in muscle–tendon lengthening are perceived as threatening, resulting in increased alpha motor neuron activation, reflexive shortening of the muscle–tendon unit, and muscle spasm. The pain–spasm cycle is illustrated in figure 8.1.

Interventions that reduce pain and heightened gamma motor neuron activity will allow for a gradual restoration of range of motion. Gamma motor neurons innervate and maintain tension within muscle spindles; thus, hyperactivity may lower the threshold to contract extrafusal muscle fibers and contribute to spasticity. Providers must use some caution when encouraging active range of motion as part of treatments to interrupt a pain–spasm cycle. Active motion should not threaten to further compromise injured tissue. Active motion, however, must precede passive interventions such as joint mobilization and stretching of the muscle–tendon unit. When a patient is unwilling to move an injured or painful region, more serious conditions such as fracture must be ruled out before proceeding with treatment. Managing a pain–spasm cycle is often necessary to fully evaluate the mechanical function of a joint and initiate interventions to restore mechanical function.

Stretch Tolerance

Muscle–tendon unit tightness can also affect joint motion during dynamic movement. Stretch tolerance refers to an individual’s ability to tolerate discomfort as muscles and surrounding tissue are stretched. Stretch tolerance differs from a pain–spasm cycle in that pain is experienced during, rather than before, activity. Two-joint muscles such as the hamstrings and rectus femoris are common muscles of concern. Tight hamstring muscles are often observed in patients experiencing patellofemoral and low back pain. Increases in flexibility after bouts of stretching, regardless of technique, are likely the result of neural responses rather than changes in muscle–tendon mechanical properties.¹ Interestingly, acute bouts of stretching have been observed to significantly improve hamstring flexibility in the contralateral limb,^2,3 which is highly suggestive of central control of stretch tolerance and thus flexibility. It has further been suggested that stretch tolerance may be mediated in the central nervous system through endogenous pain modulating pathways,⁴ suggesting that pain management may play an essential role in the maintenance of joint motion.

Mechanical Restrictions

Motion can be restricted by bone or connective tissue within a joint. Tears of the menisci in the knee and bone spurs at the olecranon process of the elbow are examples of such mechanical blocks. Interventions for such mechanically induced limitations are dependent on the tissue involved and the impact of the motion loss on the patient.

• Restrictions related to bone may warrant surgical excision when pain persists or there is a loss of function or ability to participate in activities important to the patient. However, some bone-related changes can be left alone when function is not impaired.
• Restrictions caused by other connective tissues such as a torn meniscus in the knee, sometimes referred to as a loose body, may require surgical excision but also may respond to nonoperative care.^5,6 Patients with a degenerative meniscus tear are more likely to respond favorably to nonoperative treatment.
• Nonoperative care may consist of manual therapy, stretching of extracapsular tissue (tissue outside of the joint, including muscle–tendon units), and active range of motion and exercise.

Effusion (joint swelling) associated with acute joint injury or persistent mechanical irritation can also limit motion. In general, there must be a large amount of fluid within a joint to cause a mechanical limitation to motion; however, swelling is associated with an acute inflammatory response involving pain-induced muscle spasm. Swelling associated with inflammation is resolved through activation of the lymphatic system. Lymphatic drainage is increased by muscle contraction and relaxation and active range of motion. Once such activity is deemed safe, pain-free exercise should be performed several times daily. External compression and elevation can assist in the process, but muscle activation has a greater effect on lymph movement than passive intervention.

More Excerpts From Therapeutic Interventions for Musculoskeletal Conditions With HKPropel Online Video

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