Question: Who Let the Dogs Out?

Answer: I did. Your doctor cares about your feet and you should, too. Join me in walking through basic physical exam principles using your feet as a guide.

Your feet and calves are called the “second heart” for good reason — from them you can tell a lot about your overall health. So take your shoes off, let the dogs out, and let’s get on with our exam!

Inspect the Dogs

Let us invoke our prodigious powers of observation and train them on our patient’s feet… what do they look like? Or, a better question to ask ourselves, what is our general sense? Many times, pathology can be anticipated if we sense something just isn’t quite right.

In hearing our patient’s story, we begin to develop our differential diagnosis (a list of reasons for our patient’s troubles). Then use our eyes to hunt for findings that either rule in, or rule out, those diagnoses. The things we must look for can be characterized as the 3 T’s:

• Tone — are they discolored or pale?

• Temp — are they warm or cold?

• Texture — do they have hair? Do the toenails look healthy? Is the skin thin, calloused, or swollen? Never forget to look between the toes.

Let’s practice:

66 year old woman with Hx of coronary artery disease who underwent percutaneous coronary intervention with a drug-eluting stent (CAD s/p PCI w/DES x1) and a 40 pack-year smoking history presents to our clinic with chronic crampy right leg pain that is present at rest, but worse with exertion.

Listening to this story, we begin to develop our differential. At the very top ought to be peripheral arterial disease (PAD)… for this is a classic presentation of the disease. If we are suspecting PAD, we would expect to see a pale, cold, hairless leg with thin shiny skin, dystrophic nails, and diminished pulses. If we see some, or all, of these findings, then the next step would be ABIs and a likely vascular surgery referral. If not, then we need to dig a bit deeper in the history and exam.

Pretend this is a right foot. The Dorsalis Pedis (DP) pulse can be found on the dorsal aspect of the foot, generally within the red dashes. The Posterior Tibial (PT) pulse is found palpating behind the medial malleolus. If pulses cannot be felt, a vascular doppler may be necessary.

Pet the Dogs

First we examine with our eyes, then we examine with our hands via palpation. The goal here is to assess for the 3 P’s:

• Pain - if the patient describes any sort of trauma or injury, search for any pain or deformity. Palpate along the ankle joint line, the heel, the length of each metatarsal, etc.

• Pulses - there are two. The first, and easiest, to palpate is the Dorsalis Pedis artery located on the “top” aspect of the foot. The second is the Posterior Tibial artery located “behind” the big bump on the inside of the ankle called the medial malleolus.

• (Ph)eeling - how well do our patient’s feet make sense of the world? You can think of sensation in two ways - location and type. Location refers to “dermatomes,” which are areas of skin that are innervated by specific nerve roots. Numbness in one of these areas can suggest pathology at a nerve root (or a specific nerve itself). There are also different types of sensation: light touch, pinprick, and vibration are just a few. Proprioception, which is our ability to sense where our body is in space, also falls under this category.

Let’s practice:

52 year old woman who hasn’t seen a doctor in 20 years (since her last kid was born) presents to our clinic with numbness and tingling in both her feet.

With this patient, at the top of our differential rests peripheral neuropathy. If this is truly peripheral neuropathy, on exam we would expect to see diminished sensation to light touch, pinprick, vibration, and/or proprioception. We must also rule out if there is a radicular pattern of diminished sensation,

We touch the tops of her feet simultaneously. Then we touch the bottoms. She is numb throughout. Then we touch her right foot and right shin at the same time — she states her shin feels “more normal.” We find the same to be true on the left leg. We take our monofilament wire and touch different points on the bottoms of her feet. She cannot feel any of them. We take our tuning fork, buzz it, and hold it on her big toe. She can’t feel it, either.

These exam findings: diminished sensation of bilateral feet, up to the mid-shin, with diminished light touch and vibratory sensation are indicative of neuropathy. Now the question is why does she have it? You order basic lab work including an HbA1c (for diabetes), thyroid panel, and Vitamin B12 level among others. You find her A1c is 10.5… diagnostic for diabetes, which is the most common cause of peripheral neuropathy.

Pretend this is a left foot. This is a general depiction of sensory distribution via nerve roots. Think of nerve roots as off-ramps from the main spinal cord highway. These off-ramps divide into other roads. These roads travel far from the off ramps and are referred to by different names. Though, if you trace them back long enough you’ll get right back to the off-ramp. The same is true for nerves. Here’s the point: numbness on the top of the foot can refer to injury at L5 or with the Common Fibular Nerve via the Superficial and/or Deep Fibular nerves. It’s up to us to localize the lesion.

Test the Dogs

And finally, we must always test, test, test. How strong are they? The goal here is to see if there is any discernible weakness between our patient’s limbs. If there is, this points to either a nerve injury or musculoskeletal injury.

Due to the redundancy of the lumbosacral nerve plexus, there is carryover with different nerves and muscle groups. To give an example, the hip adductors are mainly innervated by the obturator nerve, which is supplied by L2-4 nerve roots. Same with the femoral nerve, which innervates the quadriceps but is also supplied by the L2-4 nerve roots. Meaning, if you have an L3 nerve root injury you may experience weakness in knee extension, but also hip adduction.

With that being said, here’s how it breaks down (generally speaking):

• L1 = Hip flexion = Hip flexors (Psoas major, Illiacus, and Rectus Femoris)

• L2 = Hip adduction = Thigh adductors (Adductor longus/magnus/brevis and Gracillis)

• L3 = Knee extension = Quadriceps (Vastus lateralus/medius/ intermedius and Rectus Femoris)

• L4 = Ankle dorsiflexion = Shinbone muscle (Tibialis anterior)

• L5 = Big Toe extension/Hip abduction = Big Toe muscle (Extensor Hallicus Longus) and Glutes (Gluteus medius, Tensor Fascia Lata, Glute max/min to a lesser extent)

• S1 = Hip Extension/Plantar Flexion = Glute muscles (Gluteus maximus) and Calf muscles (Gastrocnemius)

• S2 = Knee Flexion = Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus)

Let’s practice:

38 year old man with no relevant medical history presents to our clinic for acute shooting pain down his right leg associated with numbness after lifting a box while helping his friend move. You find that he is numb on the lateral aspect of his right foot.

At the top of our differential here is a disc herniation (acute onset, radiating pain down leg, numbness, etc). Since he is numb on the lateral aspect of his right foot, where would you expect to find weakness on exam? What nerve root is likely involved?

He can walk on his heels, but he is unable to walk on his toes. He has no trouble plantarflexing his left ankle. However, when asked to stand on the toes of his right foot, he is unable to do so.

This is characteristic of an S1 radiculopathy. The L5-S1 disc has herniated and is compressing the S1 nerve root, causing pain, numbness on the lateral aspect of the foot, and weakness in plantarflexion. You prescribe NSAIDs, a steroid taper, and send him to physical therapy when the pain calms down with follow-up in six weeks. Well done, doc!

Keep Your Dogs from Barking

All in all, your feet are important members of your body — don’t neglect them. They are responsible for taking you from point A to B. They need good vasculature to return blood to your heart. They must feel appropriately to mitigate injury.

Maintaining general health is key to maintaining proper foot health. Exercise regularly including both strength training and conditioning. Practice proper nutrition by eating real food, getting appropriate levels of protein, and get your fruits and veggies in by “eating a rainbow.”

With your feet specifically, be sure to wash with soap and water regularly. Never forget to wash between the toes. Remember that lotion is your friend. You can use a pumice stone to gently shave down any callouses. Clip your toenails regularly… and when you do be sure to cut straight across to limit your chance of getting an ingrown toenail.

“Doctor walking his dog” - produced with Substack Image Generator. Walking is a great way to keep all your dogs healthy.

Lessons…

1. We develop our differential based off of our patient’s story and use the exam to find clues to support or reject different possible diagnoses.

2. When we examine a patient, we go from least invasive maneuvers to most invasive.

3. Take care of your feet and they’ll take care of you!

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