# The Flexor Retinaculum Connects the Surrounding Structures into the Medial Ankle Complex
## 4 Discussion  
The first contribution of the present study is that we proved the presence of connections between the FR and the DL, the SL, the FFS, the paratenon of the Achilles tendon, the AbH, and the IER in routine MRI ankle examinations. PD and T2-weighted images without fat tissue saturation make it possible to correctly distinguish even narrow bands of collagen-like retinaculum from adjacent adipose tissue [12; 13; 14]. The FR is a crural fascia-strengthening structure, having bone attachment onto the medial malleolus, together with the DL. It is a thin structure composed of layers; the most inner one is a smooth layer to enable gliding, the thick mid layer is supporting, and the outer layer of loose connective tissue covers the other two layers [6]. The FR is a broad, narrow collagen structure that reinforces the fascia posteriorly and inferiorly from the medial malleolus. It transforms the groove present on the medial malleolus into a fibrous-bone canal called the tarsal tunnel, whose function is to pass the posterior tibial tendon, the flexor digitorum longus, the posterior tibial vessels, and the tibial nerve in three separate compartments. The FR contributes distally to the tibialis posterior tendon sheath and blends with the superficial part of the DL. In its inferior extension, the FR splits to enclose the AbH and then reunites and blends with the plantar fascia [3; 6]. Literature regarding the FR is very limited, and only connections to the superficial part of the DL and the AbH were mentioned in previous studies. We revealed that the FR connects with many more medial malleolus structures. The FR is a thicker part of the crural fascia, which spans different compartments, creating space that envelopes different groups of muscles and tendons [15]. The arrangement of the crural fascia fibers is multidirectional, reflecting the various loads applied. Likewise, in our study, the FR shows connections with different structures located anteriorly, posteriorly, inferiorly, and medially to the medial malleolus, reinforcing the medial part of the ankle. As the crural fascia integrates structures located in different compartments, the FR integrates the medial ankle ligaments and the non-ligamentous structures, utilizing connections revealed in our study [15; 16]. The biomechanical unity of the fascia and the muscles is expressed by a similarity in the structure of the muscle aponeurosis and deep fascia [3; 6]. The connection between muscle and fascia can be expressed as communicating the fascial element with the tendon's compartment. However, far from a complete definition, the myofascali diseases assume that connections between the fascia and the muscle exist [15]. In our study, we demonstrated a connection between FR and FFS, paratenon, and AbH [3; 6]. The FR unites with the paratenon of the Achilles tendon in two ways. The first one is direct, and the second is indirect by branching from the FTCL. This type of connection is an example of a fascia-muscle connection, possibly for proprioception [1; 16]. The role of the FTCL is to integrate the ligaments and the fibrous bands in [PERSON]'s fat pad [10]; therefore, FTCL has a similar role to the FR in the medial ankle region. Both FR and FTCL are parts of the crural fascia. About 4% of the plantaris tendon connects with the deep crural fascia [17; 18], being an example of a fascial-tendon connection. In our study, the plantaris tendon frequency was nearly twice as high as reported previously [17; 19], which may be due to population variability. As in type 4, according to [PERSON] et al. [17], the tendon branched in the fat tissue of the Kager's triangle [18], connecting with the fascial elements, as previously described [10]. Some very narrow terminal projections of the plantaris tendon joined the anterior outline of the paratenon or the FTCL. It is a known phenomenon that lateral ankle structures communicate [9]. The interconnections between ligaments of [PERSON]'s fat pads and surrounding structures are also described in the posterior region [10].