The source for the neurological impairment can be central (spinal cord or brain) or peripheral (nerves located connecting from the spinal cord to an end-site muscle or sensory receptor).Foot drop is rarely the result of a pathology involving the muscles or bones that make up the lower leg. The anterior tibialis is the muscle that picks up the foot. Although the anterior tibialis plays a major role in dorsiflexion, it is assisted by the fibularis tertius, extensor digitorum longus and the extensor hallucis longus. If the drop foot is caused by neurological disorder all of these muscles could be affected because they are all innervated by the deep fibular (peroneal) nerve, which branches from the sciatic nerve. The sciatic nerve exits the lumbar plexus with its root arising from the fifth lumbar nerve space.Occasionally, spasticity in the muscles opposite the anterior tibialis, the gastrocnemius and soleus, exists in the presence of foot drop, making the pathology much more complex than foot drop. Isolated foot drop is usually a flaccid condition. There are gradations of weakness that can be seen with foot drop, as follows according to MRC:
0 = complete paralysis,
1 = flicker of contraction,
2 = contraction with gravity eliminated alone,
3 = contraction against gravity alone,
4 = contraction against gravity and some resistance, and
5 = contraction against powerful resistance (normal power).foot slap is a heel strike abnormality, which is the audible slapping of the foot to the floor with each step that occurs when the foot first hits the floor on each step.
Since patients tend to have weakness in the affected foot, they may not have the ability to support their body weight. Often, a walker or cane will be used to assist in this aspect.Drop Foot is the inability to dorsiflex, evert, or invert the foot. So when looking at the Gait cycle, the part of the gait cycle that involves most dorsiflexion action would be Heel Contact of the foot at 10% of Gait Cycle, and the entire swing phase, or 60-100% of the Gait Cycle. This is also known as Gait Abnormalities. Diagnosis
Initial diagnosis often is made during routine physical examination. Such diagnosis can be confirmed by a medical professional such as a physiatrist, neurologist, orthopedic surgeon or neurosurgeon. A person with foot drop will have difficulty walking on his or her heels because 
they will be unable to lift the front of the foot (balls and toes) off the ground. Therefore, a simple test of asking the patient to dorsiflex may determine diagnosis of the problem. This is measured on a 0-5 scale that observes mobility. The lowest point, 0, will determine complete paralysis and the highest point, 5, will determine complete mobility.There are other tests that may help determine the underlying etiology for this diagnosis. Such tests may include MRI, MRN, or EMG to assess the surrounding areas of damaged nerves and the damaged nerves themselves, respectively. The nerve that communicates to the muscles that lift the foot is the peroneal nerve.