If weakness cannot be traced to another systemic condition, such as diabetes, it can come from either a nerve or a muscle problem. Paralysis is the extreme manifestation of weakness.

There are many reasons people experience weakness related to low back pain, but the most common cause of overall systemic weakness is inactivity.

A person's posture, gait, step size and degree and amount of arm swing when walking all affect dozens of muscles in the middle and lower back. A minor injury that may have no symptoms can cause a person to compensate in different ways when walking, sometimes without even knowing it. Both large and small adjustments to these everyday activities can have a domino effect sometimes leading to back pain.

Causes of Muscle Weakness

Myopathy
As in dermatitis that affects the skin, and neuropathy that affects the nerves, myopathy is a systemic condition that attacks the muscle tissue, most of the time all over the body.

There are various types of myopathy, including that caused by diabetes and other endocrine abnormalities from infections and from autoimmune diseases and then there are toxic and hereditary causes.

Most myopathies show up in the muscles close to the trunk first, in the pectoral muscles in the upper extremities and the muscles in the thigh.

Symptoms
Patients with myopathy will detect a weakness walking up stairs, their knees may involuntarily buckle and they may find it harder to do routine tasks such as opening jars.

Osteoarthritis and Osteoporosis
These types of diseases that come with age and cause joint derangement sometimes followed by vertebral fractures can cause nerve damage in response to these conditions, therefore weakening muscles.

Common neurological causes of weakness include the following:

- Stroke
- Spinal Cord Injury

Injury or damage to peripheral nerves - Often the result of trauma, surgery or pressure produced by posture or position

Myopathy - One or more nerves damaged systemic problems reducing reflexes

Osteoporosis/Osteoarthritis - Weakness is sometimes a secondary symptom resulting in complications of these disorders