Approach to ankle pain: Clinical sciences

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

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

Your next step is to assess for trauma. This includes an obvious mechanism of injury, such as a motor vehicle collision or sports injury, or if there’s a joint deformity or ligamentous laxity.

If trauma is present, assess the Ottawa ankle rules, which can tell you if imaging is needed or not.

First, check to see if the patient has pain in either the malleolar or midfoot zones. Next, palpate for bony tenderness in the affected limb along the distal fibula, distal tibia, base of the 5th metatarsal, and the navicular bone. Third, determine if your patient was unable to bear weight on the affected foot immediately after their injury AND is unable to bear weight for at least four steps at the time of initial medical evaluation.

If the patient has pain in either the malleolar or midfoot zones and at least one of the other two criteria, meaning bony tenderness or inability to bear weight they meet the Ottawa rules criteria. In this case, order an ankle x-ray. If it shows a fracture of one or more ankle bones, diagnose an ankle fracture.

On the other hand, if the Ottowa rules criteria are not met, the likelihood of fracture is low, so an X-ray is not indicated. At this point, diagnose an ankle sprain or strain.

Here’s a clinical pearl! Ankle sprains are very common and generally seen in teens and young adults. The most common type is lateral ankle sprain caused by inversion ankle injury. Another important and more serious type is a high ankle sprain which is caused by damage to the tibiofibular syndesmosis. This can happen with high-impact sports such as football.

Alright, let’s take a step back. If trauma is not present, assess for signs of infection like fever, chills, myalgias, and localized tenderness. If there are signs of infection, think septic arthritis or osteomyelitis.

Patients with septic arthritis typically have a history of immunosuppression or pre-existing joint disease. Physical examination may reveal ankle joint effusion, limited range of motion, and erythema with warmth of the overlying skin. Based on these findings, consider septic arthritis of the ankle and aspirate synovial fluid for analysis of cell count and differential, gram stain, culture, and the presence of crystals. If the synovial fluid has a cloudy or purulent appearance, a white blood cell count of 50,000 or more, the gram stain and culture are positive for bacteria, and the sample is negative for crystals, diagnose septic arthritis.

Next up is osteomyelitis. Next to fever, patients often have a history of diabetic neuropathy, peripheral vascular disease, or chronic ankle ulcers. History might also reveal risk factors such as tobacco use or immunosuppression. On physical exam, you’ll typically see tenderness to palpation, erythema, and edema of the overlying skin. There might also be fistula tracts or ulcerations on the skin.

Based on these findings, consider osteomyelitis of the ankle 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 reveal positive blood cultures, often with leukocytosis and elevated ESR and CRP. X-ray may show a lucent bone lesion with an overlying periosteal reaction or cortical erosion, while the MRI shows diffuse bone marrow and soft tissue edema, where there is also periosteal reaction and an adjacent complex collection might be present. In this case, you can diagnose osteomyelitis.

On the other hand, if there are no signs of infection, assess for neuropathic ankle 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 decreased sensation to pinprick and allodynia, which is when pain is elicited from something that typically doesn’t cause pain like a feather. In this case, consider neuropathy.