Approach to foot pain: Clinical sciences

Foot pain is a common symptom with many underlying causes, including conditions affecting the joints, bones, tendons, or skin. It’s important to first identify if your patient’s foot pain is due to trauma or infection. Other possible types of foot pain include neuropathic pain due to nerve damage; nociceptive pain due to arthralgia, ostalgia, or tendinopathy; and dermatologic ulcers or lesions.

When a patient presents with foot pain, first obtain a focused history and physical exam. History typically reveals foot pain, while the exam might demonstrate foot edema, erythema, or warmth. They may also have foot tenderness, effusion, limited range of motion, or crepitus.

Your next step is to assess for trauma. This includes an obvious mechanism of injury, such as a motor vehicle crash or sports injury, joint deformity, or ligamentous laxity. If trauma is present, think fracture or dislocation, and investigate further.

Patients with a fracture or dislocation will report pain that may worsen with activity and improve with rest. They might also report bruising. Physical exam will reveal tenderness to palpation and difficulty bearing weight. With these findings, consider a traumatic injury, such as a fracture or dislocation, and order a foot X-ray. If the X-ray results confirm a bone fracture or joint dislocation, diagnose a foot fracture or dislocation!

Now, here’s a clinical pearl to keep in mind! Stress fractures are caused by repetitive stress, such as frequent running, marching, or dancing. Patients with this condition may have a history of osteoporosis, tobacco use, vitamin D deficiency, or calcium deficiency. Their initial X-rays might be negative or show a faint fracture line, while an MRI typically shows fracture or osseous remodeling.

Alright, if trauma is not present, assess for signs of infection like fever, chills, myalgias, and localized tenderness. If there are signs of infection, think osteomyelitis. Patients with osteomyelitis often have a history of diabetes mellitus, tobacco use, immunocompromised status, or chronic foot ulcers.

Physical examination may reveal that the foot is tender to palpation with edema, erythema, and warmth. There might be fistula tracts or ulcerations on the foot as well. Based on these findings, consider osteomyelitis and order labs, including blood cultures, CBC, and inflammatory markers like ESR and CRP. Also, make sure to order imaging, including an X-ray and an MRI.

Labs will reveal positive blood cultures, possibly with leukocytosis; and the ESR and CRP could be elevated. The X-ray can be normal or may show overlying soft tissue swelling with cortical bone destruction and an underlying lucent bony lesion; while the MRI typically reveals bone marrow edema and overlying periosteal and subcutaneous edema. In this case, diagnose osteomyelitis.

On the other hand, if there are no signs of infection, assess for neuropathic foot pain. This type of pain is lancinating, electrical, radiating, burning, or cold in nature. If neuropathic pain is present, the patient might report a history of numbness and tingling in their feet, as well as a history of a systemic disease associated with neuropathy, such as diabetes mellitus or multiple myeloma.

Physical exam reveals an abnormal monofilament exam, decreased sensation to pinprick, and possibly allodynia, which is when pain is elicited from something that typically doesn’t cause pain, like a feather.

Although these findings strongly suggest neuropathy, you might need to order a nerve conduction velocity study, or NCV, and an ultrasound or MRI to confirm. If the NCV shows an abnormal nerve conduction and if imaging shows nerve compression, diagnose neuropathy.

And here’s another clinical pearl! There are many possible causes of neuropathic foot pain. Peripheral neuropathy can lead to sensory loss and decreased ankle reflexes. Another possible underlying condition is nerve entrapment, such as tarsal tunnel syndrome, which results from compression of the tibial nerve as it passes under the flexor retinaculum of the ankle. Lastly, Morton neuroma is caused by recurrent compression of one of the common plantar digital nerves.

Okay, if neuropathic foot pain is not present, assess for nociceptive foot pain. This type of foot pain is localized, dull, or sharp. It does not radiate, has an identifiable pain source, and usually involves joints, bony structures, soft tissues, or skin. If this is the case, assess the primary tissue involvement to determine the source of the pain.

First, let’s discuss arthralgia. These patients may have a history of joint stiffness, fatigue, or malaise. The exam may show joint erythema, edema, and warmth with possible joint deformity, limited range of motion, or crepitus. If this is the case, diagnose arthralgia.