Sensations and muscle movement in the leg are controlled by a network of nerves and muscles that work together to send signals from the brain to the leg. Problems in the transmission of nerve signals or muscle structure can lead to pain in the leg, as well as leg weakness.
Polymyositis
Polymyositis belongs to a group of muscle disorders called inflammatory myopathies. This condition is characterized by weakness of the muscle that occurs in conjunction with muscle inflammation. Polymyositis affects the skeletal muscles, which are the muscles responsible for body movement. It's a gradual disease that first attacks the proximal muscles, which are the muscles closet to the middle of the body. This causes leg weakness, resulting in difficulty walking, climbing stairs and getting up from a seated position, according to the National Institute of Neurological Disorders and Stroke. Eventually, the distal muscles, which are farther away from the trunk of the body, become weak. Other symptoms of polymyositis include arthritis, shortness of breath, difficulty speaking and irregular heartbeat. Although polymyositis can't be cured, a combination of medications, physical therapy and increased exercise may improve symptoms.
Muscular Dystrophy
Muscular dystrophy is a genetic disorder characterized by gradual weakening of muscles. Those who inherit muscular dystrophy lack a specific protein that's essential in building and maintaining muscle tissue, according to Kids Health. There are several forms of muscular dystrophy; each progress at a different rate than the others. General symptoms of muscular dystrophy include leg muscle weakness that affects the ability to walk and muscle weakness in the arms, back and shoulders. Many of those with muscular dystrophy require the use of a wheelchair. There is no cure for muscular dystrophy, but physical therapy and medications may help improve muscle strength and lessen symptoms.
Herniated Disk
Disks are small pads of cartilage between the vertebrae of the spinal column that provide cushion and support for the bones. The disks are made up of two layers: the outer layer, called the annulus, and the inner layer, called the nucleus. A herniated disk occurs when the nucleus pushes through the annulus and exerts pressure on one of the spinal nerves. The pressure on the nerve causes pain, tingling and numbness that radiate from the buttock to the leg, weakness in the lower back and one of the legs and lower back pain, according to MayoClinic.com. A herniated disk usually develops due to the normal weakening of disks from the aging process but may also occur from lifting heavy objects or physical trauma. Most herniated disks correct themselves over time. Bed rest and pain medication can be useful in alleviating symptoms. Severe cases may require surgery to repair the disk.
