Introduction
Peroneus tendons are the two tendons of the short and long fibula muscle (old name: Musculus peroneus longus et brevis; newer name: Musculus fibulais longus et brevis), which represent the attachment and thus also the connection between the foot bones and the musculature of the calf-side lower leg. The long fibula muscle originates at the upper end of the fibula and runs along the rear outer side of the fibula in the direction of the foot, and then moves behind the outer ankle and under the foot and attaches to the inner side of the first metatarsal. The short fibula muscle follows a similar course, but is shorter in name, and thus originates a little further down the fibula, to be joined later to the outer edge of the fifth metatarsal.
The function of both muscles is to extend the foot downwards (plantar flexion), to spread the foot or to move the foot away from the center of the body and to lift the outer edge of the foot or to bend the foot axis inwards (pronation). Both muscles also stabilize the foot during walking. Both tendons of the fibula muscles run in a bony groove surrounded by a connective tissue sheath (retinaculum). This groove allows the tendon to sit or slide securely and ensures optimal force transfer to the foot. If the fibula muscles are chronically misused or overstressed, this can lead to a reactive inflammation of one or both peroneal tendons or to the so-called peroneal tendon syndrome, which is sometimes characterized by severe pain and discomfort during certain foot movements.
Cause
Inflammation of tendons (tendovaginitis; tendinosis) is usually caused by permanent overloading, where inflammation of the tendons themselves and/or the tendon sheaths surrounding the tendons occurs in response to chronic friction of the tendon in its bony abutment. Overloading of the musculature or the muscle-tendon attachments results on the one hand from sudden, highly stressful movements without sufficient, preceding muscle warming, and on the other hand from incorrect or unaccustomed training with a too rapid increase in load over the course of time. In addition, permanent incorrect loading due to anatomical malpositions can also cause tendon inflammation.
Especially in the foot area, incorrect footwear and foot malpositions, such as the O-shaped bending of the foot outwards (varus position of the ankle) can lead to peroneal tendon inflammation. It is also possible that anatomical bone variants can lead to permanent irritation of the peroneal tendons, as may be the case with peroneal tubercle (bony protrusion in the area of the outer ankle) or a bony spur on the fibula. In some cases, the inflammation of the peroneal tendons can also be caused by an infection or as part of an inflammatory rheumatism.
