Overview

The nervous system is a crucial and complex system that is responsible for controlling movement and sensation in our bodies. The nervous system is made up of two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, whilst the PNS is made up of nerves that extend out from the spinal cord and branch off into all parts of the body. The nerves in our nervous system are composed of billions of neurones and have many roles in the body. We have motor neurones that help control our movement and sensory neurones that help us respond to touch, sounds, taste, light, smell. Our nervous system also controls aspects such as our “fight or flight” response, release of adrenaline, regulating our digestive system, dilating our eyes and keeping our heartbeats regular.¹

There are two very important nerves in our body that help us in particular with sensory and motor function, the sciatic nerve, and the peroneal nerve. These two nerves run down our legs and are significant in the functionality of our lower limbs.¹ Despite being anatomically close, injuries to these two nerves present different clinical symptoms and it is important to recognise these differences in order to accurately diagnose and give appropriate treatment. In this article, we will explore the differences in anatomy and function of the sciatic and peroneal nerve, how they can be injured, the symptoms they may present and their respective treatment options.

Anatomy and function of the sciatic and peroneal nerves

Sciatic nerve

The sciatic nerve is the longest nerve in the body and travels from the bottom of your spine, through your pelvis and then down the back of your thighs and calves. It contains both movement and sensory fibres and helps you with functions such as standing, walking, running and feeling sensations in your legs. There are five different nerve roots that make up your sciatic nerve. Two roots start in your lower back (lumbar spine), and three roots start at the bottom of your spine (sacrum), these all join together at the base of your spine. Your sciatic nerve splits into two main branches at your knees: the common peroneal nerve and the tibial nerve.^2,3

Peroneal nerve

The peroneal nerve, also known as the common peroneal nerve, is a branch of the sciatic nerve. It starts at the tops of your hips and travels down the backs of your legs until it reaches the knees where it wraps round to the front of your leg and goes way to your toes giving you the ability to feel sensations in the front and sides of your legs as well as controlling the muscles in your legs allowing you to move your ankles and toes. As well as your sciatic nerve your peroneal nerve also splits into two main branches around your knee, the deep peroneal nerve which controls the movement of your first two toes, and the superficial peroneal nerve which controls the function of the rest of your toes as well as the sensation in your foot and lower legs.^4,5

Clinical presentation and symptoms

Symptoms of both sciatic and peroneal nerve injury often present similar symptoms but have a few significant differentiating factors.

Sciatic nerve injury symptoms

Injury to your sciatic nerve is called sciatica. There are two types of sciatica:

• True sciatic – which is any injury that affects your sciatic nerve directly
• Sciatic-like conditions – any condition that feels like sciatica but happens for other reasons and happens to relate to the sciatic nerve^2,3

Symptoms of both types of sciatica include:

• Pain – can feel like an aching, burning or electric shock-type pain down the back and leg, which occurs due to pressure on the sciatic nerve such as when sneezing, when bending your back or legs and lying down, in severe cases, this can become chronic/long-term⁶
• Numbness – inability to feel sensations on and in your leg and foot, in severe cases, this can become permanent²
• Tingling (paresthesia) – otherwise known as “pins and needles” and feels like your leg is asleep²
• Muscle weakness – causing difficulty in walking due to your nerve signals being disrupted and not being able to reach your legs or feet²
• Inability to control bladder or bowels – the most severe symptom, the nerves that also control your bladder and bowel functions are affected causing urinary incontinence and/or faecal incontinence⁶

Peroneal nerve injury symptoms

Symptoms of peroneal nerve injury include:

• Foot drop – most common symptom and where your ankle is unable to flex when taking a step forward, causing you to catch your toes on the ground, and so you lift your knee higher than the other to bring your foot up, creating a “dropping” motion affecting the way you walk⁷
• Aching or burning pain in the lower leg and foot
• Loss of sensation or numbness in the lower leg or foot
• Weak movement or completely unable to move the foot or flex toes and ankles upward⁵

Causes of injury

Sciatic nerve injury

Sciatica is common in adulthood, and over 40% of us will experience sciatica in some form in our lifetime. Common causes or conditions that can cause sciatica include:^2,3

• Traumatic injuries – e.g. hip dislocations, pelvic fractures, penetrating injuries
• Herniated discs – spinal disk bulges out
• Degenerative disc disease – the cushioning between your spinal vertebrae (bones) becomes worn
• Tumours or cysts
• Blood clot
• Osteoarthritis – most common type of arthritis where your bones rub together
• Bone spurs (osteophytes) – hard bumps that grow on bone
• Spinal stenosis or foraminal stenosis – spinal canal becomes narrow, squashing your spinal nerves
• Spondylolisthesis – spinal vertebrae (bones) can slip onto the vertebrae underneath
• Cauda equina syndrome – a bundle of nerves called the cauda equina at the bottom of your spinal cord becomes squashed
• Piriformis syndrome – your piriformis (glute/butt) muscle starts to compress your sciatic nerve
• Pregnancy

There are also many other risk factors that can increase the likelihood of you developing sciatica, which can include:

• Type 2 diabetes
• Sitting down for too long and being very inactive
• Heavy lifting and not lifting correctly
• Smoking and using other tobacco products
• Obesity
• General wear and tear from old age
• Having a previous or current injury to spine or lower back

Peroneal nerve injury

Causes of peroneal nerve injury often occur due to traumatic injuries to your lower leg such as:⁴

• Knee fracture, ankle fracture or fibula fracture
• Knee dislocation
• Blood clot
• Tumour

There are also other risk factors and conditions that can increase the chance of you developing peroneal nerve injury such as:

• Previous or current knee or ankle injury
• Too tight compression of leg
• Type 2 diabetes
• Being underweight
• Rheumatoid arthritis
• Anorexia
• Charcot-Marie-Tooth disease – a genetic condition affecting control of your muscles

Diagnosis and tests

If you are presenting these symptoms, see a doctor and they will be able to determine which kind of injury you have. Your doctor will ask you about your symptoms and first perform a clinical exam that involves seeing how you walk, squat, flex your feet and lift your legs.²

They will then likely ask you to take an imaging test such as:

• MRI scan
• CT scan
• X-ray
• Electromyogram (EMG)
• Nerve conduction study⁴

Management and treatment

Depending on how severe the injury is you may need surgery, but in most cases, self-treatment options can be used to help manage milder cases and alleviate long-term symptoms.

Sciatic nerve injury treatment

• Surgery
  • Discectomy – removal of parts of herniated disk to reduce pressure on your spinal nerves
  • Laminectomy – removal of a section of your spinal vertebra called the lamina to reduce pressure on the spinal nerves
• Pain medication – such as pain killers
• Spinal injections – such as corticosteroids to reduce inflammation
• Physical therapy – core muscle strengthening, aerobic and stretching exercises
• Other therapies – such as using ice packs, heat packs, massage therapy, yoga, acupuncture and seeing a chiropractor to help relieve pain and discomfort²

Peroneal nerve injury treatment

• Surgery – this usually involves nerve decompression, nerve repair or replacing damaged nerves with donor tissue
• Physical therapy – to strengthen foot
• Orthotic support – such as shoe inserts like braces, splints or ankle-foot orthosis (AFO) to assist with foot drop and walking with a proper gait⁴

Summary

The sciatic and peroneal nerves are important in movement and sensation of our lower body. Their injuries have similar symptoms but have some significant differences that differentiate them in their clinical presentation, despite their anatomical connection. Sciatic nerve injuries often result in lower limb pain, numbness, tingling, weakness, and in some severe cases, loss of bladder or bowel control. Peroneal nerve injuries, on the other hand, primarily cause foot drop, difficulty in flexing the ankle, and pain and sensory loss along the lower leg and foot. While sciatic nerve injury is commonly due to traumatic injuries and conditions like herniated discs and degenerative disc disease, peroneal nerve injury is mostly associated with knee dislocations or fractures. Understanding these key differences is essential for accurate diagnosis and appropriate treatment, which may involve physical therapies, pain management, or surgical intervention depending on severity.