Mystery Diagnosis: The Case of the Swollen Ankle


Test your diagnostic skills with this puzzling patient presentation.

The old adage, “Things may not always be what they seem,” is true in many life situations, but especially in health care.

Confounding signs and symptoms sometimes lead health care practitioners to draw incorrect conclusions. Therefore, our Mystery Diagnosis cases emphasize that physical therapists need to consider primary care physicians’ recommendations but investigate each new case with an open mind, looking beyond the obvious to draw their own conclusions and develop an objective diagnosis.

When a patient complains of a red, swollen ankle, the first diagnosis to spring to mind is often a sprained ankle, but by conducting a thorough examination and asking a range of questions, physical therapists may find new clues suggesting other possibilities.

The Referral

“Joe Smith,” an 18-year-old athletic man in the midst of Air Force cadet basic training, limped slightly into the office of Michael Fink, PT, DSc, SCS, OCS. The day before, he had seen his primary care physician for a red, swollen ankle. The primary care physician believed he had a lateral ankle sprain, referring Smith for a physical therapy assessment.

Fink, who was serving in the U.S. Air Force at the time, is an Operation Enduring Freedom/Operation Iraqi Freedom combat veteran with nine years of active duty service as a United States Air Force physical therapist. He is now an assistant professor within the Physical Therapy Department at Lebanon Valley College, Annville, Pa., and a part-time clinician at Madden Physical Therapy, Harrisburg, Pa. Fink began the subjective portion of his evaluation, asking the patient how he hurt his ankle.

“I have no idea,” Smith replied. “I just woke up and it was really swollen and quite red. I may have twisted it yesterday during the obstacle course.” When Fink asked about his pain level, Smith replied that his ankle wasn’t very painful and he felt more of a tightness and tension from the swelling. Describing the location of the pain, Smith pointed to the left lateral malleolus of his left ankle, which was red and swollen. His gait was slightly antalgic but he didn’t require an assistive device. The local skin temperature over the lateral malleolous was slightly elevated.

Fink began conducting a series of tests on Smith. “His ankle range of motion was primarily limited by the swelling not the pain,” he said, but he observed no other significant limit. Next, Fink performed special tests, such as the anterior drawer test, which assesses the integrity of the anterior talofibular ligament, and a talar tilt test to test the integrity of the calcaneofibular ligament. Both tests were negative for ligamentous laxity.

In addition, he performed a tibia-fibula compression test of the mid and lower part of the leg to test for a possible fracture or a syndesmotic disruption of the interosseous membrane, which also had normal results. Furthermore, the patient had normal results when Fink performed a Kleiger test, with passive dorsiflexion and eversion of the foot to assess for a possible deltoid ligament tear and subsequent syndesmotic sprain. Fink also palpated the area where the patient felt swelling.

Although the patient did not have diagnostic images, Fink did not believe they were warranted in accordance with the Ottawa ankle rules, a set of guidelines developed to indicate whether a patient with an acute ankle injury requires radiographs to identify a possible fracture.

Closer to an Answer

“My suspected diagnosis after I completed the battery of tests was that he indeed did not have a lateral ankle sprain and that the redness and swelling were possibly due to something like a cellulitis, a common skin infection caused by bacteria,” he said.

Based on this suspicion, he proceeded to search for what he calls “portals for infection”, such as an open wound. He found an open blister on the sole of the patient’s heel. “It didn’t appear to be infected, but it gave me that portal for infection that I was looking for. I reasoned that the open blister could have been a local site of infection that could have then gone into his ankle,” he said.

Consequently, Fink referred the patient back to his primary care physician, suggesting the patient might have a case of cellulitis and require antibiotic treatment. On reexamining Smith, the physician agreed that this could be the case and prescribed a course of antibiotics.

Fink saw Smith two days later. “Within two days the swelling, redness, everything was down and his ankle was back to normal,” Fink said. The patient’s gait also had returned to normal.

Lessons to Learn

Fink explained that there are a number of take-away messages for physical therapists from such a case. “I think one of the biggest perils is that sometimes nonmusculoskeletal systemic problems can often be mistaken for a musculoskeletal problem, if they closely mimic signs and symptoms of a common musculoskeletal problem and are in a location where we would expect that common musculoskeletal problem to arise,” Fink said.

He also explained that such infections are common if a patient has poor hygiene. Furthermore, when patients don’t remember how an injury occurred, it’s critical to ask additional questions, gathering as much information as possible to determine whether it is truly an injury or an infection or systemic reaction. “Just from a cursory look, anyone would think it was a lateral ankle sprain,” Fink said. “It was in the right location. The swelling was about the right amount. The redness looked about the right degree. He had slightly increased local skin temperature. The difference was in the mechanism of injury, or lack thereof.”

Tricks of the Trade

Fink has developed a few strategies to help him pinpoint a diagnosis in such cases. For example, if he’s not sure whether the patient has an ankle sprain or cellulitis, he outlines the area of redness with a permanent black marker. He explains to the patient that if he or she is following the proper guidelines for an acute ankle injury, such as applying ice to the area and elevating the foot, the redness shouldn’t proceed beyond the black ink boundaries. The redness should fade within the boundaries. He further explains to the patient: “If it’s a cellulitis and you’re not getting the antibiotic treatment that you need, you will begin to see the redness creep beyond those boundaries that I’ve created. In severe cases, you can even see red streaking going up the leg or down into the foot.” Furthermore, this should happen within a day or so.

Above all, to ensure patients will receive an accurate diagnosis, leading ultimately to the care they need, physical therapists need to keep an autonomous mind even after reading the physician’s diagnosis on the referral. “Is the diagnosis they’re coming in with, truly what is going on? Not always.” Fink said.

The opinions or assertions contained herein are the private views of the authors or sources and are not to be construed as official or as reflecting the views of the Departments of the Air Force or Defense.


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Diane Donofrio Angelucci

Diane is a freelance writer.

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