Evaluating Foot Pain in Elderly Patients

Introduction

Functional problems in the foot are common, and the examination of the feet of an older person is an especially important part of a geriatric evaluation. Because the feet are the most distant body parts from the heart and central nervous system, early clues of cardiovascular and neurologic illness may initially appear there. Neglected feet and poor foot hygiene reflect compromised self-maintenance skills that are often the result of physical or mental illness. The examination can be organized into orthopedic and neuromuscular, dermatologic, neurologic, and vascular observations. Each foot should be examined in detail.

Always check the shoes for abnormal wear; particularly look at the soles for asymmetry. Have the patient stand facing away from you and examine his or her stance for foot and ankle misalignment. Check the gait. Walking heel to toe is normal. Look for flat feet or a toe-to-heel walk, which can indicate equinus contracture.

Orthopedic and Neuromuscular Observations

Carefully inspect the anatomic landmarks. Atrophy of the anterior muscles (foot dorsiflexors) suggests foot drop.

Now inspect the toes, foot, and arches. Note the following:

• Lateral deviation of the great toe is hallux valgus (bunion deformity).
• Hypoplasia of the 4th and 5th toes suggests spina bifida occulta and an associated predisposition to urinary incontinence.
• Plantar atrophy is an early sign of thromboangiitis obliterans, also known as Buerger's disease (Samuels' sign). This condition is mostly seen in male smokers between the ages of 20 and 45.
• Medial displacement of the Achilles tendon when viewed from behind suggests pes planus (Helbing's sign).

Check passive ankle range of motion.

• Decreased inversion or eversion suggests a problem with the subtalar joint.
• Decreased dorsiflexion or plantarflexion implies tibiotalar joint dysfunction.
• Painless bony irregularities around the joint in the absence of prior trauma suggest a Charcot joint.

Next, examine active and passive foot motion:

• Check active plantar flexion with knee at 90 degrees (have the patient "step on the gas"). Weakness suggests S1 nerve root damage or tibial nerve dysfunction, tibiotalar ankle sprain, gastrocnemius muscle tear, and Achilles tendon damage or tendonitis.
• Check active dorsiflexion of the foot against resistance. Weakness suggests foot drop (L5), tibiotalar ankle sprain, and extensor tendonitis.
• Check dorsiflexion of the great toe. Weakness implies foot drop or L5 lesion, first metatarsal phalangeal joint problem, or extensor hallucis longus tendonitis.

Next check ankle inversion and eversion against resistance:

• Weakness on inversion with resistance implies foot drop (L5), subtalar ankle sprain, or anterior tibialis tendonitis.
• Weakness on eversion with resistance suggests superficial peroneal nerve problem (S1), subtalar ankle sprain, or peroneal retinaculum sprain.

Dermatologic Observations

Note the skin over the ankles and feet. Normally, the feet of an older person (or a person with long-standing diabetes mellitus) are dry and appear "dusty" as a result of mild autonomic dysfunction, with a relative lack of sweating. Wet feet suggest alcoholism or alcohol withdrawal (especially in an elderly person who becomes anxious at night in the hospital). Note any calluses and varicosities. An ulcer on the foot suggests neuropathy, vascular insufficiency, or diabetes; a nonhealing foot ulcer suggests possible melanoma or other malignancy.

Rashes. The presence of a rash may suggest the following:

• A rash on the dorsum of the foot is usually caused by eczema, tinea pedis, or bacterial superinfection.
• A rash on the instep of one foot suggests tinea pedis. If the rash is bilateral, also consider tinea rubrum and eczema.
• Hyperkeratosis of the soles suggests tylosis (look for gastrointestinal malignancy), psoriasis, or eczema.
• A rash between the toes can be caused by tinea pedis, Candida sp, eczema, psoriasis, or erythrasma.

Toenail Abnormalities. A variety of conditions can produce changes in the toenails. Extensive discussion of toenail findings is beyond the scope of this article; however, fingernails have many findings in common with toenails. See Examining the Fingernails When Evaluating Presenting Symptoms in Elderly Patients for an article about examination of the fingernails. Perhaps the most common abnormal finding in toenails is nail thickening from onychomycosis. Gout can produce a transverse depression (Beau's line) in the nail of the great toe after an attack of podagra. Toenails take about a year to grow out from the cuticle to the free edge, so you can estimate when the attack occurred by the position of the line on the toenail. For example, a line halfway up the right great toe (but not the left) can imply an attack of gout 6 months previous.

Edema. If edema is present, determine whether the fluid is protein-rich or protein-poor (hypoalbuminemic) in origin. Push into the edema fluid to produce a pit and check recovery time. Protein-poor fluid will spring back quickly (like pushing into a water-filled balloon) and suggests hypoalbuminemia caused by hepatic or renal disease or malnutrition. Protein-rich fluid retains the pit for more than a minute, which suggests cardiac disease (congestive heart failure) or inflammation.

Edema can also suggest the following:

• Diffuse edema with redness and warmth suggests deep venous thrombosis, superficial thrombophlebitis, or cellulitis (check for tinea pedis between the toes).
• Brawny hyperpigmented skin with edema suggests chronic venous insufficiency.
• Seeing a purpuric chevron over the lateral malleolus suggests a ruptured Baker's cyst.

Vascular Observations

Search for clues of peripheral vascular disease by simultaneously feeling the pulses on each side of the foot, such as the dorsalis pedis and posterior tibial. A diminished pulse on one side implies a vascular process on that side. The dorsalis pedis pulse is usually felt along the dorsum of the foot just lateral to the extensor tendon of the great toe. The posterior tibial pulse is usually just behind and slightly below the medial malleolus.

Look for a wide pulse pressure (greater than 60 mm Hg), which in elderly people, can be seen with fever, aortic insufficiency, systolic hypertension, thyrotoxicosis, or complete heart block. It can be detected in an octogenarian by feeling bounding foot pulses and can also be observed in visibly pulsing (and often tortuous) arteries.

Evaluate the capillary refill to check small vessel integrity. Use the 3-second rule. Press the vascular bed (such as on the great toe). If the blanching discoloration returns to normal in less than 3 seconds, the vessels are normal. Delayed capillary refill of more than 3 seconds suggests peripheral vascular disease (Moschcowitz' sign).

Neurologic Observations

The next step (pun intended) is the examination for sensory defects involving the foot, which include deep tendon and pathologic reflexes. For neuromuscular examination, see Orthopedic and Neuromuscular Observations, above.

Testing for Sensation. Check pinprick and light touch over the dorsal, medial, and lateral foot for sensation. The source of innervation of the medial foot and great toe is L4, the dorsum of the foot is L5, and the lateral foot is S1.

Lack of sensation to pinching the Achilles tendon suggests neurosyphilis (Abadie's sign).

Vibration Test. Check vibration sense by placing a tuning fork on the great toe. Sometimes it is useful to first touch the tuning fork on a bony prominence at the patient's elbow or wrist to give the patient a sense of the vibration. Let the patient's toes warm up if the weather is cold. Decreased vibration sense at the great toe suggests peripheral neuropathy. If the sensation is abnormal, move up the leg to the ankles and then the patella. Note that vibration can only reliably be tested over a bony prominence.

Great Toe Proprioception: To check great toe proprioception, first have the patient close his or her eyes or shield the patient from seeing your movements. Hold the toe by the sides and move it toward the patient's head in a large upward movement. Then move the toe downward away from the head. Have the patient say "up" or "down" depending on the direction of movement that he or she senses. Then perform the test by moving the toe about 2 mm and note the patient's response. Making the small movements and holding the toe by the sides are worth stressing.

Ankle Jerk Reflex. Test the ankle jerk reflex to evaluate the L5-S1 nerve roots. Have the patient kneel on a chair or the examining table. For a bedfast patient, cross one knee over the opposite knee, slightly dorsiflex the foot and tap the Achilles tendon. Watch for downward movement of the foot. Then, actively dorsiflex the patient's foot after 2 or 3 rapid flexions and extensions. A rhythmic beating of the foot for multiple beats will indicate clonus, which is never normal and implies either sympathetic excess (such as alcohol withdrawal) or pyramidal tract disease. Sharp dorsiflexion of the foot producing clonus is Charcot-Vulpian sign.

Other Flexion Tests. Passive plantar flexion of the toes producing dorsiflexion of the foot and knee flexion (Bekhterev's reflex) implies previous stroke. Plantar flexion in response to tapping the dorsum of the foot (Mendel's sign) suggests upper motor neuron disease. Adduction and inversion of the foot to medial foot stroking suggests pyramidal tract disease (Hirschberg's sign).

Babinski's Reflex. Support the patient's ankle and stroke the sole of the foot from the lateral aspect across the base of the toes. A normal response is plantar movement of the great toe. An abnormal response is dorsiflexion of great toe and fanning of other toes. Bilateral cortical, spinal, or pyramidal tract lesions may produce a crossed response where both toes react. In the setting of forefoot amputation, you can look for contraction of the tensor fascia lata when stimulating the sole (Brissaud's reflex ). The table shows some Babinski's equivalents with the same great toe response.

Table. Babinski's Equivalents

Signs of Endocrine or Metabolic Disorders

Cramping of the calves and feet can be an early sign of diabetes mellitus (Unschuld's sign). Eversion of the foot when tapping over the peroneal nerve suggests hypocalcemia (peroneal sign). (Note: This is the author's favorite way to determine hypocalcemia because it seems to be the first sign to appear and the last to disappear.) Tenderness to percussion over the tibia suggests hypochromic anemia (Golonbov's sign). Exquisite pain of the great toe when touching the fifth toe joint suggests gout (Plotz' sign).