Sensory nerve endings in the anterior cruciate ligament (Lig. cruciatum anterius) of sheep

Abstract

This study examines the structure of sensory nerve endings in the sheep anterior cruciate ligament (ACL). Three types of nerve endings are found: free nerve endings (FNE), Ruffini corpuscles, and lamellated corpuscles. The FNE (more than 100) are found subsynovially. The afferent nerve fibres are either thin myelinated axons (Adelta) or C fibres with diameters of 1-2 microm. FNE have been reported to function as thermoreceptors and polymodal nociceptors. In addition, FNE are also seen between fascicles of collagen fibres, often close to blood vessels. Part of this group may be efferent autonomic fibres controlling local blood flow. The corpuscles are seen subsynovially and between fascicles of connective tissue close to the attachment points of the ACL. A ligament contains about 20 Ruffini corpuscles, which are mainly located in the subsynovial connective tissue. They consist of cylinders formed from perineural cells surrounding the afferent myelinated axons (diameters 4-5 microm) with enlarged nerve terminals anchored between collagen fibres. These enter in bundles from the surrounding connective tissue at one open pole, pass through the length of the cylinder, and leave at the other pole. Functionally, Ruffini corpuscles have been described as slowly adapting stretch receptors. Lamellated corpuscles (usually between 5 and 15) are found in the subsynovial connective tissue. The afferent myelinated axon has a diameter of 4-6 microm, and the nerve terminal is located in the centre of numerous layers formed by lamellated terminal glial cells and by a perineural capsule. They are known to function as rapidly adapting pressure receptors. The most important function of the ACL is its mechanical function, but additional sensory functions must be considered triggering reflex mechanisms in case of extreme positioning or overload.

The innervation pattern of the human Achilles tendon: studies of the normal and tendinosis tendon with markers for general and sensory innervation

“…Sensory corpuscles possessing a lamellated appearance were occasionally identified in the paratendinous connective tissue. In accordance with previous studies on corpuscles in the cruciate ligament of the sheep (Halata et al 1999) and the limbs of the mouse (Albuerne et al 2000), the lamellated corpuscles exhibited central axons displaying PGP9.5 immunoreaction. The previously known corpuscles in human Section of Achilles tendinosis tendon stained for PGP9.5.…”

“…9). They appeared as lamellated (Pacinian) corpuscles (e.g., Halata et al 1999;Albuerne et al 2000). The central axons showed marked PGP9.5 immunoreaction (Fig.…”

Model-based ankle joint angle tracing by cuff electrode recordings of peroneal and tibial nerves

“…Joint capsule receptors encoded information about joint angle, angle velocity, and local stress of joint capsule [6,16]. Ligament receptors include stretch and pressure receptors [8]. Even though feedback from muscle spindle receptors is the most important source of proprioceptive information, all these afferents together contribute to the integrated perception of movement and posture.…”

Effects of knee bracing on postural control after anterior cruciate ligament rupture

“…the ligamentous control of tibial translation in the ventral direction and rotation, the ACL also plays an important role in knee joint proprioception. Surgical ACL reconstruction not only restores mechanical stability after a period of healing and remodeling but also allows patients to more efficiently train knee joint proprioception and restore neuromuscular control [3,4,6,17,43]. The greatest challenge for physicians and patients alike is to improve the neuromuscular control system and achieve adequate coordination of movement.…”