Is foot drop assessment performed below or above the knee?

From the Guidelines

Foot drop assessment should be performed both below and above the knee to determine the cause and guide treatment. This comprehensive approach is necessary because foot drop can result from various pathologies including common peroneal nerve compression at the fibular head, L4-L5 radiculopathy, peripheral neuropathy, or even central nervous system disorders 1.

Key Components of Foot Drop Assessment

• Examine the foot and ankle for weakness in dorsiflexion, which is the hallmark of foot drop
• Test ankle dorsiflexion strength against resistance and assess for inversion and eversion weakness
• Extend the examination above the knee to evaluate for potential proximal causes
• Check knee flexion and extension strength, hip muscle function, and perform a thorough neurological examination including reflexes (particularly the patellar and Achilles reflexes), sensation testing along specific nerve distributions, and straight leg raise testing The pattern of associated muscle weakness and sensory changes helps localize the lesion - for example, isolated peroneal nerve palsy typically causes foot drop with sensory loss on the dorsum of the foot, while an L5 radiculopathy may present with additional hamstring weakness 1.

Importance of Comprehensive Assessment

A comprehensive foot evaluation is crucial to identify risk factors for ulcers and amputations, and should include inspection of the skin, assessment of foot deformities, neurological assessment, and vascular assessment, including pulses in the legs and feet 1. Treatment depends on accurate localization, ranging from ankle-foot orthoses for symptom management to addressing specific underlying causes such as nerve decompression or managing disc herniation.

From the Research

Foot Drop Assessment

• Foot drop assessment is typically performed to determine the cause and severity of the condition, which can be caused by various factors such as nerve injuries, neuropathies, or muscle weakness 2, 3.
• The assessment may involve a thorough neurological evaluation, including the examination of hip abductor power, to differentiate between lumbar radiculopathy and peroneal neuropathy 4.
• Nerve conduction and electromyographic studies can also be useful in localizing the site of injury and establishing the degree of damage 3.
• Imaging studies such as ultrasonography, CT, and MR imaging can help establish the cause of foot drop, whether it be at the level of the spine, along the course of the sciatic nerve, or in the popliteal fossa 3.

Assessment Location

• The assessment of foot drop can involve examination of the lower leg, including the common peroneal nerve, which innervates the ankle joint and foot extensors 2.
• The assessment may also involve examination of the hip and thigh, including the sciatic nerve, to determine if the foot drop is caused by a more proximal lesion 3, 4.
• In some cases, the assessment may be performed above the knee, such as in cases of lumbar radiculopathy or sciatic nerve injury 4.
• However, the specific location of the assessment (above or below the knee) is not explicitly stated in the provided studies, and it is likely that the assessment location depends on the individual patient's condition and the suspected cause of the foot drop.