Foot Drop: Causes, Symptoms, and Treatment

Foot drop is caused by disruption to the common peroneal nerve which controls active dorsiflexion of the ankle leading to a lack of heel strike during gait hence the term foot drop.

Foot Drop

Clinically Relevant Anatomy

The common peroneal nerve is the smaller and terminal branch of the sciatic nerve which is composed of the posterior divisions of L4, 5, S1, 2. The nerve can be palpated behind the head of the fibula and as it winds around the neck of the fibula.

Commonly, with damage to the common peroneal nerve, there will be weakness of tibialis anterior and other key dorsiflexors of the foot.\

Mechanism of Injury / Pathological Process

The common peroneal nerve is in a particularly vulnerable position as it winds around the neck of the fibula. It may be damaged at this site by:

Trauma or injury to the knee
TKA
Neurological disorders i.e. stroke
Compression of the fibula head during surgery e.g. tourniquet
Fracture of the fibula
Fracture to tibial plateau
Patellar dislocations (33% chance of nerve damage)
Ankle inversion injury

Clinical Presentation

Typical presentation of foot drop can be noted when testing the foot and ankle in isolation, however, in a clinical setting, it may be identified initially through gait assessment.

Foot and Ankle

When testing the foot and ankle a positive test for foot drop is NO active dorsiflexion in a non weight bearing position.

It is important to test passive ROM to ensure the ankle is not stiff.

Gait Assessment

Gait should be assessed in any clinical setting.

Foot drop gait can manifest in different ways varying from patient to patient.

Some patients may increase the amount of hip flexion they produce on the effected side therefore, clearing the floor more effectively:

Other patients may circumduct the hip and drag the forefoot along the floor:

Pain
Neurogenic pain can be experienced from damage to the common peroneal nerve.
This pain can be present over the lateral aspect of the knee as well as the dorsal part of the foot.
Sensory changes can also be experienced indicating nerve damage to the therapist

Foot Drop

Diagnostic Procedures

Subjective History: emphasis on any knee trauma, recent spinal/peripheral limb surgery or family history of neurological disease

Assessment of ankle dorsiflexion
Neurological exam
Gait assessment
Electromyography (EMG) / Nerve conduction studies

Outcome Measures

Foot and ankle disability index
Functional gait analysis
Stanmore assessment of foot drop
Hand dynamometry of the dorsiflexors in the foot using the Oxford scale

Foot Drop

Management / Interventions

Following palsy of the common peroneal nerve, the main residual symptom can be foot drop due to the disruption to L4/5 muscle groups which perform dorsiflexion.

This has been shown to resolve in two-thirds of patients by one-year post-injury.

Pain should also be addressed if the patient is experiencing neuropathic pain by use of appropriate analgesia.

One way to improve function while the foot drop resolves is the use of splinting.

A solid ankle-foot orthoses (AFO) or foot-up splint can be used to keep the foot in plantar-grade.

These work to increase the amount of dorsiflexion the foot is held in during gait and can prevent falls as the toes do not get caught on the floor.

Exercise

Physiotherapy interventions normally are focused on graded exercises to encourage active dorsiflexion and muscle recruitment. These exercises have been shown to prevent atrophy and speed up recovery but more research is needed.[2]

In neurologically impaired patients such as Charcot‐Marie‐Tooth disease improved with strengthening exercises to tibialis anterior, however, other neurological diseases like muscular dystrophy strength training was not found to be effective at reducing the foot drop.

Preventing contractures and stiffness is also an important maintenance goal of physiotherapy as this is likely in neurological disease patients more so than after trauma to the knee.

Electro-stimulation of the affected muscle groups has also been shown to improve recovery times.

Surgery

Direct repair of the common peroneal nerve is possible for surgical intervention however, this has been shown to have poor outcomes with residual foot drop leading to further surgery.

In extreme cases tibialis posterior can be transposed to regain active dorsiflexion by using the tendon not innervated by the common peroneal nerve, this surgery has been shown to be more successful than nerve repair.

Surgery has been shown to be successful at improving active dorsiflexion strength and reduced use of AFOs.