Cite This Article

Duong, H. Marshall, J. Tomesch, A. Achilles Heel - Kager’s Fat Pad. Ortho Pearls. February 5, 2025; Available: https://www.orthoempearls.com/articles/i-declare-a-thumb-war2l

What is the diagnosis?

Achilles tendon rupture. 

What is the mechanism of injury?

Ruptures typically occur after high-impact loading, often in plantar flexion, of the lower extremity. Regularly seen in high velocity sports requiring frequent acceleration and deceleration. 

What physical exam findings are expected?

Strength testing can show weakness on plantar flexion when compared to the uninjured lower extremity. Palpation can demonstrate a lack of continuity of the achilles tendon. Special testing includes the Thompson/Squeeze test where the patient is lying prone and the calf is squeezed to observe for appropriate plantarflexion. A positive Matles test demonstrates a neutral or dorsiflexed ankle when a patient is lying prone with their legs flexed at 90 degrees. Typically, plantarflexion is expected. 

What imaging modalities can be used?

Ankle X-rays are often the first line for reported ankle injuries. Approximately 25% of achilles tendon ruptures are misdiagnosed [1]. Some x-rays can reveal an effusion/edema near Kager’s fat pad within Kager’s triangle (a radiolucent area seen in lateral ankle x-rays which is the region bordered by the flexor hallucis longus muscle/tendon, achilles tendon, and calcaneus). Distorsion here can sometimes demonstrate achilles pathology in the proper clinical context [2][3][4]. 

 

Image 3 (left).  Image provided by radiopaedia.org, case contributed by Domenico Nicoletti, rID: . Lateral ankle X-ray demonstrating Kager’s triangle as flanked by anatomical landmarks. This x-ray demonstrates calcific tendinosis as shown by calcifications posteriorly and mixed heterogeneity in kager’s fat pad.

Image 4 (right). Author’s own images. Distortion of Kager’s fat pad secondary to edema with concern for achilles pathology. 

Ultrasounds are quick diagnostic tools that can also aid in the diagnosis of achilles tendon ruptures 

Image 5. Author’s own images. Ultrasound image demonstrating disruption of the achilles tendon with surrounding hypoechoic edema. 

MRIs have historically been used to diagnose achilles tendon ruptures in the outpatient setting however studies have suggested that physical exam findings are sufficient in diagnosis of achilles tendon ruptures [5].

What is the management in the ED/when should you consult orthopedics?

Orthopedic surgery does not need to be consulted in the Emergency Department for management. 

In the Emergency Department, if there is high suspicion for achilles rupture, the patient should be splinted in slight plantar flexion in order to shorten the distance between the achilles tendon and its attachment point. They should be instructed to be non-weight bearing until follow up with sports medicine or an orthopedic surgeon. Though previous studies showed a possible higher risk of re-rupture with conservative management alone, new evidence has shown similar rates of re-rupture between conservative and surgical management [6][7].