Lower extremity spasticity is a condition marked by involuntary muscle tightness and stiffness in the legs. It is not a disease but a symptom of damage to the brain or spinal cord. This damage disrupts the nerve signals that control muscle movement, impairing the pathways that tell muscles to relax. The result is a state of overactivity, like a faulty “off switch,” where muscles receive too many signals to tighten and not enough to relax. The experience can range from mild tightness to severe, painful spasms that interfere with movement.
Underlying Neurological Causes
Spasticity arises from damage to upper motor neurons, which are the nerve cells in the brain and spinal cord that signal the muscles to move. This damage disrupts the balance of signals, causing excessive muscle activity. This is the common element across several neurological conditions. A primary cause is stroke, where a loss of blood flow damages brain tissue responsible for motor control.
Multiple sclerosis (MS) contributes to spasticity when the immune system damages the protective myelin sheath around nerve fibers, impairing signal transmission. Traumatic brain injuries (TBI) and spinal cord injuries (SCI) can physically sever these nerve pathways. Other conditions like cerebral palsy (CP), a group of disorders affecting movement and posture, involve spasticity due to developmental brain damage. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that also leads to worsening muscle stiffness.
Symptoms and Associated Complications
A primary characteristic of lower extremity spasticity is increased muscle tone (hypertonia), where leg muscles feel constantly stiff. Patients often experience involuntary muscle spasms and clonus, a series of rapid, rhythmic shakes most commonly felt in the ankle. These symptoms can cause abnormal gait patterns, such as a “scissoring” motion where the knees and thighs press together or cross while walking.
If left unmanaged, spasticity can lead to significant long-term complications. One of the most serious is the development of joint contractures, where muscles and tendons become permanently shortened, leading to stiff, bent joints and loss of mobility. This stiffness and the associated spasms can cause chronic pain, making daily activities difficult. Prolonged immobility also increases the risk of developing pressure sores on the skin, and stiffness can create challenges with personal hygiene.
The Diagnostic Process
Diagnosing lower extremity spasticity begins with a clinical evaluation. A doctor will review the patient’s medical history for underlying neurological conditions and perform a physical examination to assess muscle tone, reflex activity, and joint range of motion. Gait analysis, the systematic study of how a person walks, helps identify characteristic patterns associated with spasticity, such as toe walking or scissoring of the legs.
To objectively measure the severity of the condition, clinicians use standardized assessment tools. The Modified Ashworth Scale is used to grade muscle tone by assessing the resistance felt when moving a limb passively. Another tool, the Tardieu Scale, helps differentiate between spasticity and a fixed contracture by assessing the muscle’s reaction to being stretched at different speeds. These scales provide a baseline to track the condition’s progression or response to treatment.
Treatment and Management Strategies
Physical and occupational therapy form the foundation of treatment. Physical therapists focus on stretching and strengthening exercises to improve flexibility, while occupational therapists help individuals adapt daily activities like dressing and bathing. Bracing or splinting may be used to maintain proper limb position and prevent contractures.
When therapy alone is insufficient, oral medications are often introduced. Drugs like baclofen and tizanidine act as muscle relaxants, working systemically to reduce overall muscle tone. These medications can be effective but may cause side effects such as drowsiness or muscle weakness, requiring careful management.
For spasticity concentrated in specific muscle groups, botulinum toxin (Botox) injections can be administered directly into overactive leg muscles to selectively relax them. This approach provides relief for several months and can improve comfort and the effectiveness of physical therapy.
In severe cases that do not respond to other treatments, more advanced interventions may be considered. An intrathecal baclofen pump is a surgically implanted device that delivers medication directly to the spinal fluid, allowing for a lower dose and fewer systemic side effects. Surgical procedures, such as tendon lengthening or a selective dorsal rhizotomy, may also be performed to provide long-term relief.