Understanding Weakness in Parkinson’s disease

Muscle weakness and Parkinson’s disease

It is common for people with Parkinson’s disease (PD) to describe themselves as feeling weak. They may say that their legs are “heavy”, feel like they’re “made out of lead”, or feel like they’re “in concrete.” And they may also feel weak all over or describe weakness in their hands or arms.

Person holding weak knee.

From a medical perspective, however, weakness is officially defined as decreased muscle strength. Do people with PD actually have decreased muscle strength in their arms and/or legs? Alternatively, when people with PD say they are “weak”, are they actually describing other symptoms of PD?

Research about weakness in PD

An interesting research study sought to figure this out, focusing on weakness in the legs. Ninety people with PD and fifty-two aged-matched controls (people without PD) were studied. The participants were asked whether they perceived “lower limb weakness”, “heavy legs”, or “fatigued legs”. Reporting one of these abnormal leg sensations was much more common in people with PD (69%) than in controls (21%). The leg strength of the participants was then measured 1) on a clinical exam (how strong the participants pushed with their legs against the examiner’s hand) and 2) using specialized equipment that measured leg strength. Interestingly, actual muscle strength did not differ between the two groups in two of the three ways that muscle strength was tested.  

This study implies that something else may be responsible for these abnormal leg sensations in people with PD which is not attributable to an actual decrease in muscle strength. The study investigated other PD symptoms and how they correlated with the perception of leg weakness. 

The abnormal sensations were more common in people with PD who reported the non-motor symptoms of fatigue and orthostatic hypotension. They also correlated with various measures of PD motor symptoms including leg bradykinesia, decreased facial expression, decreased spontaneous movement, difficulty rising from a chair, walking difficulties, freezing of gait, and postural instability.

These correlations could mean that when people notice weakness in the legs, they are in fact identifying one of several possible PD motor or non-motor symptoms that may be responsible.

What could cause a sensation of weak legs?

Parkinson’s motor symptoms

Although a person with PD’s legs may not actually be weak, the perception that they are weak may be because of other motor symptoms of PD such as slowness of movement or bradykinesia, and problems with walking. People with PD often describe that their movements are not fluid and that they are not in full control of their leg movements. These changes can be perceived as weak legs.


Fatigue is a common but under-recognized non-motor symptom in PD, defined as an unpleasant sensation of lacking energy, which makes the performance of routine activities, physical or mental, a strain. Fatigue can lessen the desire and ability to perform activities of daily living, interact with friends and family, and participate in social activities.

There can be many causes of feeling fatigued in the setting of PD. Because of this, the first step in addressing fatigue is to analyze why fatigue is occurring and to try to improve the underlying issue. Poor sleep, depression, as well as other medical conditions such as thyroid imbalance or anemia, can contribute to fatigue. All these issues can be successfully treated, so speak with your doctor about fatigue if it is a problem for you. For some people, medications taken for the motor symptoms of Parkinson’s disease can cause fatigue. In this case, altering the regimen of PD medications can help. Being in poor physical condition can worsen fatigue, so for some people, exercise can improve fatigue. Fatigue is often due to a combination of these and other factors. In some cases, a person with PD does not have any of these identifiable causes but still feels fatigued. When this is the case, the fatigue may be due to PD itself with nerve loss in parts of the brain that control wakefulness.

Orthostatic hypotension

Neurogenic orthostatic hypotension (NOH) is a neurologic condition that prevents your body from properly regulating your blood pressure when you change position, particularly when you go from lying or sitting to standing up. NOH typically causes dizziness or lightheadedness when changing head position, but it can also cause other symptoms such as a sensation of generalized weakness.

NOH can be diagnosed by checking your blood pressure when you are in various positions. If you do have this issue, multiple lifestyle changes can help including gradual changes in head position when moving from lying to sitting to standing, increasing fluids and salt in your diet, and using compression stockings. Multiple medications can also be used to manage low blood pressure.

Increased frailty

Frailty is a general age-related decline in reserve and function which leaves a person with the decreased ability to withstand medical stressors. Some of the clinical features of frailty include decreased energy, diminished physical activity, slowed walking, and unintentional weight loss. Frailty is linked to advanced PD and could be what people with PD describe as weakness.

Treating weakness in Parkinson’s disease

Since the cause of muscle weakness in Parkinson’s disease can be varied, the first step is to talk with your health care team about it so they can try to determine the source of the issue.  Any treatment or next steps will depend on what is causing this feeling of muscle weakness, or weak legs. Treatment may include medication(s) to treat the symptom, physical therapy, exercise, nutrition changes, or possibly a combination of several tactics to alleviate this issue.

Tips and takeaways

  • It is common for people with PD to describe having weak legs, or feeling weak, even though their leg strength may be normal.
  • Other motor or non-motor symptoms of PD may be responsible for the sensation of weak legs including: leg bradykinesia, gait disorder, fatigue, NOH, increased frailty.
  • If you are experiencing an overall feeling of weakness, or weak legs, be sure to talk to your doctor about it so that solutions or improvements can be found.

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