Muscle Stiffness · What Is It, Causes, Treatment, and More

Muscle stiffness refers to a sensation of muscle tightness, which often causes pain and makes it challenging to move. Muscle stiffness may occur after overuse of a particular muscle, or it may indicate an underlying condition.

There are three types of muscle: skeletal, cardiac, and smooth. Muscle stiffness primarily affects skeletal muscle, which is a voluntarily-controlled type of muscle that enables humans to move and perform daily activities. In general, these actions are possible after a signal from the nervous system stimulates contraction of the skeletal muscle, resulting in movement. If any problems interfere with the communication between the nervous system and the muscle cells, the muscles may remain contracted and result in stiffness.

Muscle stiffness most commonly arises after the overuse of skeletal muscles, which tends to happen after a long period of minimal motion (e.g., after extended bed rest) or after engaging in new exercises. These actions can cause temporary damage to the muscle cells, leading to stiffness. Muscle stiffness from overuse of the muscles occurs most frequently among people who do not exercise often.  

Electrolyte imbalances may also cause muscle stiffness, especially after exercise. Electrolytes (e.g., sodium, potassium) are important minerals in the body that play a role in conducting nerve impulses and contracting muscles, among other functions. When a person exercises, electrolytes are lost with water (e.g., sweat), making it more difficult for the nervous system to facilitate muscle movement.

Muscle stiffness can also develop due to an underlying myopathy, or a disease of the muscles, which can result from metabolic, inflammatory, endocrine, infectious, or medication-related causes. Metabolic disorders, such as mitochondrial disease and McArdle’s disease, disrupt the balance of nutrients and energy in the body. Inflammatory conditions, such as polymyalgia rheumatica, are characterized by increased inflammation in the body due to an overreaction by the body’s immune system. Endocrine disorders, like hypothyroidism and acromegaly, are caused by hormone imbalances in the body. Disruptions in metabolic processes, the immune system, and hormone levels can all produce muscle stiffness. Infections, such as the flu, COVID-19, and meningitis, are also often associated with muscle stiffness. Finally, muscle stiffness can occur as a side effect of certain medications, such as statins, which are prescribed to treat high cholesterol, or anesthetics, which are commonly given during surgery. 

Since muscle movement depends on communication between the nervous system and the muscles, muscle stiffness can also arise from issues with the nerves and muscles (i.e., neuromuscular disorders) or problems affecting only the nerves (i.e., neurologic disorders). Stiff-person syndrome, a rare cause of muscle stiffness, is a type of neuromuscular disorder in which motor neurons can cause involuntary muscle spasms. Other disorders, such as Parkinson disease, myasthenia gravis, and Lambert Eaton syndrome, are characterized by progressively worsening muscle stiffness, or rigidity. Individuals with a history of stroke may also experience muscle stiffness.

Since a variety of factors can induce and worsen muscle stiffness, diagnosis focuses on determining the underlying cause. A clinical assessment begins with a review of the individual’s history of muscle stiffness, signs and symptoms, past medical history, and a physical examination. During the physical exam, a clinician may ask the individual to perform certain movements in order to determine if the muscle stiffness has impaired their range of motion. Depending on the suspected cause of stiffness, additional diagnostic tests may be performed. 

If the suspected cause of muscle stiffness is related to inflammatory, metabolic, or endocrine related conditions, various blood tests may be conducted to determine the primary disorder. 

When neuromuscular or neurologic disorders are indicated, further assessment often includes nerve conduction studies to test nerve function and needle electromyography to test muscle responsiveness. Blood tests may also be used to screen for markers of certain conditions, such as glutamic acid decarboxylase (GAD) antibodies for stiff-person syndrome. Diagnosis of other conditions may require imaging studies, such as magnetic resonance imaging (MRI).

Muscle stiffness treatments are dependent upon the cause. Muscle stiffness due to overuse of skeletal muscles will eventually dissipate over time, and conservative, at-home treatments may help. Individuals may experience relief from stiffness after resting the muscles, alternating between applying ice packs and heating pads, stretching, or massaging the muscle.

However, treatment for muscle stiffness due to an underlying condition may involve physical therapy or medications. A physical therapist may work with the individual to improve strength and mobility through a series of exercises. Pain medications, like non-steroidal antiinflammatory drugs (NSAIDs), may be suggested to manage pain associated with muscle stiffness. Some individuals who have neuromuscular diseases, such as stiff-person syndrome, may be prescribed anticonvulsants or intravenous immunoglobulin. Treatment for Parkinson’s disease and other neurologic diseases may include medications that stimulate the release of dopamine, a neurotransmitter. Depending on the underlying cause of muscle stiffness, additional treatments may be necessary.

Some muscle stiffness may be prevented by exercising regularly and eating balanced, nutritious meals. Moving more often and stretching can improve muscle strength and flexibility, which may protect against muscle stiffness.