Leg pain

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Contents

Introduction

Leg pain is a common problem, which in most patients is benign and self-limiting. Anatomically the leg refers to that part of the lower limb below the knee, athough when discussing leg pain, it commonly refers to any part of the lower limb - the buttock, thigh, leg and foot.

There are a few terms that are regularly used when discussing leg pain: sciatica, claudication and antalgic gait being the important ones.

  • Sciatica - is a symptom not a disease. It is a syndrome characterized by pain radiating from the back into the buttock and into the lower extremity along its posterior or lateral aspect; the term is also used to describe pain in the distribution of the sciatic nerve
  • Claudication - lower limb pain on walking, possibly associated with lameness or limping
  • Antalgic gait - a limping gait as a result of a painful lower limb

Aetiology

Leg pain will result from an injury or compression of any neural structure supplying the leg; reduction in blood flow or disturbance of venous return; injury to the soft tissue structures of the leg; injury, inflammation or neoplasm involving the bony structures of the leg and pain referred to the leg from the abdomen and pelvis.

Pathology

Causes of leg pain presents the common clinical problems, their presentation, level and type of pathology.

Table 64. Causes of leg pain
Clinical problem Presentation Region of pathology Pathology
Neural - spinal
Sciatica Radiating leg pain (Table 76.2) Nerve root compression spinal canal or exit foramen

Disc prolapse (Axial T2 MRI of the lumbar spine - the arrow points to a large central L4-L5 disc prolapse causing secondary canal stenosis and nerve root entrapment. The smaller sagittal view confirms the L4-L5 disc prolapse and a large L3-L4 disc prolapse.)

Lateral recess stenosis

Osteophyte ((A) Sagittal lumbar myelogram - grade I L4-L5 spondylolisthesis with secondary canal stenosis. L3-L4 lumbar canal stenosis. (B) Post-myelogram CT scan of lumbar spine - marked facetal degeneration and hypertrophy (black arrow), lumbar canal stenosis (white arrow) and lateral recess stenosis (white arrowhead).B)

Synovial cyst

Spondylolisthesis ((A) Sagittal lumbar myelogram - grade I L4-L5 spondylolisthesis with secondary canal stenosis. L3-L4 lumbar canal stenosis. (B) Post-myelogram CT scan of lumbar spine - marked facetal degeneration and hypertrophy (black arrow), lumbar canal stenosis (white arrow) and lateral recess stenosis (white arrowhead).A)

Foraminal stenosis
Tumour
Neurogenic claudication Bilateral leg pain, pins and needles, heaviness Multiple roots under compression in the spinal canal Lumbar canal stenosis
Facet hypertrophy
Ligamentum flavum hypertrophy
Diffuse disc bulge
Spondylolisthesis
Venous hypertension or ischaemia of the spinal cord Dural arterio-venous fistula
Neural - peripheral nerve
Meralgia parasthetica Burning pain, numbness anterolateral thigh Lateral cutaneous nerve of thigh Entrapment under inguinal ligament medial to anterior superior iliac spine
Piriformis syndrome Pain in sciatic distribution Sciatic nerve Entrapment by piriformis muscle
Common peroneal nerve entrapment Weak ankle dorsiflexion and anterolateral leg pain Common peroneal nerve Trapped as it winds around the head of fibula
Tarsal tunnel syndrome Burning pain in the plantar surface of foot Posterior tibial nerve Flexor retinaculum from medial malleolus to calcaneus
Morton's neuralgia Pain in third web space of foot and adjacent toes Digital nerve in foot Compression between metatarsal heads
Vascular
Acute vascular compromise
Vascular claudication
Varicose vein/Venous insufficiency
Deep vein thrombosis
Joint/bony
Degenerative arthritis
Rheumatoid arthritis
Bony pathology - fracture, infection, malignancy
Soft tissue - muscle
Ligament
Joints - facet, sacroiliac, symphysis pubis, hip, knee, ankle, foot
Referred
Retroperitoneal pathology
Appendicitis
Inguinal hernia
Aortic dissection
Renal colic
Axial T2 MRI of the lumbar spine - the arrow points to a large central L4-L5 disc prolapse causing secondary canal stenosis and nerve root entrapment. The smaller sagittal view confirms the L4-L5 disc prolapse and a large L3-L4 disc prolapse.

(A) Sagittal lumbar myelogram - grade I L4-L5 spondylolisthesis with secondary canal stenosis. L3-L4 lumbar canal stenosis. (B) Post-myelogram CT scan of lumbar spine - marked facetal degeneration and hypertrophy (black arrow), lumbar canal stenosis (white arrow) and lateral recess stenosis (white arrowhead).

Clinical presentation

Neural compression of spinal origin

Presentation

Sciatica is a common clinical problem and the commonest cause is entrapment of the nerve root in the lumbar spinal canal or the exiting foramen by a disc prolapse or foraminal stenosis (see Causes of leg pain for possible causes).

The pain is often unilateral and involves one or more of the nerves from L4 to S1. Patients complain of sharp shooting pain, often originating in the buttock and radiating down the leg in the distribution of the nerve root under pressure (the sciatic nerve is not under pressure - rather a nerve root that contributes to the formation of the sciatic nerve). The pain is often associated with numbness, pins and needles and tingling, typically in a dermatomal pattern (see (A) Dermatomal pattern of sensory supply. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 183, by Frank H. Netter. (B) Nerve root supply of muscles. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 182, by Frank H. Netter.A for dermatomal patterns). Patients can go on to develop weakness (see (A) Dermatomal pattern of sensory supply. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 183, by Frank H. Netter. (B) Nerve root supply of muscles. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 182, by Frank H. Netter.B for myotomal patterns) in the distribution of the nerve root. Patients may occasionally develop leg pain as a result of pressure on the L3 and rarely L2 nerve root, and will radiate to the anterior thigh and knee.

(A) Dermatomal pattern of sensory supply. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 183, by Frank H. Netter. (B) Nerve root supply of muscles. Adapted from The CIBA Collection of Medical Illustrations, Vol 1. Nervous System, Part II: Neurologic and Neuromuscular Disorders, p. 182, by Frank H. Netter.

The patient presents with an antalgic gait, a tilt of the torso away from the affected side, avoids sitting or does so with the leg straightened at the hip and flexed at the knee. This posture tends to relieve the stretch on the nerve and help with pain control.

Examination reveals limitation of straight leg raising, limited back movements, altered sensation, numbness or weakness in the distribution of the nerve root. An absent reflex aids significantly in confirming the root involved.

Be wary of the patient whose pain has resolved but still has numbness or weakness or has bilateral leg pain. Alarm bells must ring if the patient has any sense of numbness of the saddle area or has any suggestion of difficulty with micturition or incontinence. The patient may have a large disc prolapse that can cause a cauda equina syndrome (compression of the cauda equina - the lumbosacral nerve roots in the lumbar spine - resulting in sacral anaesthesia plus bowel and bladder disturbance). A cauda equina syndrome is a neurosurgical emergency and requires urgent surgery.

An understanding of the anatomy of the lumbar spine helps to determine which nerve root is likely to be compressed. The most frequent clinical picture is a posterolateral L4-L5 disc prolapse causing an L5 radiculopathy. At L4-L5, the L4 nerve root has passed inferior to the pedicle to pass through the L4-L5 foramen and is superior to the L4-L5 disc. Thus an L4-L5 posterolateral disc prolapse will trap/compress the nerve crossing the disc (L5 root) and exiting via the foramen below (L5-S1 foramen). However, in rare instances a foraminal disc prolapse will affect the nerve exiting through its foramen (an L4-L5 forminal disc compressing L4 nerve root).

Neurogenic claudication is characterised by bilateral leg pain, worse with walking but can be present when upright and standing still and improves with a change in posture (as compared to vascular claudication, which resolves with rest, irrespective of the posture of the patient). The pain is an ache-like discomfort, often with pins and needles, heaviness, and tiredness of the legs, with variable numbness and a sense of weakness with walking. Lumbar canal stenosis is the commonest cause (see Causes of leg pain for other causes).

Examination is often unremarkable and hyporeflexia may be the only finding.

Thoracic or cervical myelopathy is a rare cause of leg pain. Occasionally compression or pathology in the spinal cord in the thoracic or cervical spine can result in a syringomyelia (a cavity in the spinal cord) that can cause leg pain.

Investigation

A lumbar spine X-ray is important as it will exclude any obvious fracture, slip/malalignment or destructive lesion involving the vertebra. A computed tomography (CT) scan of the lumbar spine will provide greater information regards the vertebral bodies, discs, facet joints, spinal canal and intervetebral foramina. In most instances a good quality CT scan of the lumbar spine will reveal the presence of a disc prolapse. The other pathologies to be excluded are lateral recess stenosis, foraminal stenosis, and synovial cysts. Beware that occasionally a very large sequestrated disc prolapse can occupy most of the spinal canal and thus be missed when interpreting the CT scan.

The investigation of choice is an MRI of the lumbar spine, as it provides better visualization of the thecal sac and nerve roots. If an MRI is contraindicated a myelogram and post-myelogram CT scan can provide the necessary information.

Management

More than 80% of the patients with sciatic respond to non-operative treatment - being a combination on analgesia, anti-inflammatories, judicious rest balanced with exercise - especially walking. Patients also need to avoid factors that will exacerbate the pain - thus avoid heavy lifting, repetitive bending and twisting. The role of physiotherapy is to re-educate the patient in terms of posture, exercises to strengthen back, abdominal and pelvic muscles and stretches.

The role of warm/cold therapy, massage, acupuncture, hydrotherapy in the acute stage is uncertain and unpredictable. The patient must be cautioned against manipulation as it may precipitate a larger disc prolapse and a cauda equina syndrome.

In the acute setting the benefit from epidural steroids or foraminal steroids is not predictable and more likely to succeed in patients that have a small disc bulge or a foraminal disc prolapse.

The role of non-surgical treatment for neurogenic claudication is limited in patients with significant symptoms. They may have some benefit from analgesia, anti-inflammatories, physiotherapy and hydrotherapy; however, in view of the mechanical compression, decompression offers the best long-term result.

Surgical intervention is indicated in the patient with intractable pain, failure to respond to medical therapy, and those that have a neurologic deficit. Most surgical patients have a better than 90% success rate of control of the leg pain provided the clinical picture matches the imaging.

Patients that have a disc prolapse and have failed non-operative treatment would benefit from a microdiscectomy and neurolysis. Those with lumbar canal stenosis require a decompressive laminectomy, lateral recess decompression and neurolysis. In either situation, the presence of instability will require an instrumented fusion.

Entrapment neuropathies

The pain is restricted to the distribution of the nerve root and thus a good history and examination can often provide the diagnosis.

These syndromes (meralgia parasthetica, piriformis syndrome, tarsal tunnel syndrome, Morton's neuralgia) present primarily with pain restricted to the distribution of the nerve under pressure (Causes of leg pain). Medical therapies with an anticonvulsant (carbamazepine) or antidepressant (amitriptyline) can provide good control of their symptoms. The alternative is a diagnostic and therapeutic block with local anaesthesia and steroids. Should this fail, surgical decompression of the nerve should be considered.

Vascular

The vascular causes are described in greater details in Chapters 52 and 54.

  • Acute arterial vascular compromise. It is caused by trauma or acute arterial occlusion of a diseased artery by a thrombotic or embolic event. The patient presents with leg pain and parasthesia with coldness and pallor. Acute intervention to restore circulation is vital to preserve limb function.
  • Vascular claudication - It is a well-recognized and common problem of leg pain, often calf pain. The pain is worse with walking and improves with rest. The pain is often a cramp-like pain in the muscles of the legs with a sense of tiredness and fatigue. Pain at rest is present with very severe disease. This is a result of progressive arteriosclerotic disease and the distribution of the pain reflects the site of arterial disease. Patients may benefit from bypass surgery.
  • Venous disease - Incompetence of the valves of the veins of the lower limb result in progressive gravitational congestion of the leg. This results in a painful, achy swollen leg that improves with rest and elevation of the leg. A major associated complication is thrombophlebitis and consequent risk of deep vein thrombosis. Surgery is only indicated in major vascular incompetence.

Joint/bone pain

  • Joint pain as a result of acute inflammation as seen in rheumatoid disease, connective tissue disease, gout or septic arthritis is often acute, associated with swelling, redness and tenderness of the joint with radiation up or down the leg.
  • Gout is a metabolic disorder characterised by an excess of uric acid in the blood. It usually presents in middle-aged men with rapid-onset painful swelling of a joint - usually the first metacarpophalangeal joint - which is red, hot and associated with proximal and distal pain. It must be differentiated from septic arthritis and other causes of leg pain discussed above.
  • Septic arthritis is often bacterial in origin, presents with pain, swelling, redness and tenderness of a joint with radiation. Inflammatory markers are abnormal and patients require antibiotics and possibly aspiration or irrigation of the joint.
  • Pain from wearing down of the cartilage of the articular surface is a progressive event and thus the pain has an insidious nature and progresses over a long period.
  • An injury or inflammation of the joint capsule, tendon and muscle around a joint can also simulate joint pathology with secondary leg pain. Both muscle and joint pain can occur from metabolic and connective tissue disorder; thus these patients may require a blood screen looking at ESR, RhF, ANF and a rheumatology review.
  • Sacroiliitis, arthritic changes in the hip, knee, ankle or arch of foot will cause local and radiating pain.

Referred

Pathology of any of the structures in the abdomen, retroperitoneum and pelvis can result in this. In most of these patients the pain is likely to be nonradiculopathic, with no dermatomal pattern unless there is involvement of the lumbosacral plexus.
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