Quantitative evaluation of nutritional pathways for the posterior cruciate ligament and the lateral collateral ligament in rabbits

The cruciate ligament of the knee receives its nutrition from a direct vascular supply and by permeation of nutrients from the synovial fluid. The contributions of these two routes as nutritional pathways are not known in detail. In this study, we injected [³H]methyl glucose as a tracer intravenously or directly into the knee of rabbits. Tracer concentrations in plasma, synovial fluid, the posterior cruciate ligament (PCL), and the lateral collateral ligament (LCL) were analysed by a pharmacokinetic compartment model. The contribution of [³H]methyl glucose permeation from the synovial fluid during steady state was calculated at 44.3% in the PCL and at 39.0% in the LCL. Although these results indicated that more than half the nutrition for both ligaments is provided by its vascular supply, synovial fluid permeation is also an important transport route for small molecules for the PCL and the LCL, which is an extra-articular structure.     

A biochemical study of the distribution of collagen and its crosslinks in knee ligaments and the patellar tendon

Purpose: The purpose of this study was to investigate biochemical differences in collagen crosslinks from different locations within the ligaments and a tendon of the human knee.

Materials and Methods: The anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), lateral collateral ligament (LCL), and patellar tendon (PT) were obtained from 24 cadavers (13 men and 11 women) whose average age at the time of death was 84.8 years. Ligaments and PT samples were obtained from the femoral and tibial insertions and the midsubstance. Hydroxyproline (Hyp) and collagen crosslinks, including pyridinoline (Pyr) and pentosidine (Pen), were compared among the different sites.

Results: The midsubstance Hyp concentration was greater than at the femoral and tibial insertions in the ACL (p?=?0.00124 and 0.000255, respectively) and PCL (p?=?0.00036 and 0.042, respectively). The Pyr:collagen ratio did not differ among sites in any of the ligaments or PT. The Pen:collagen ratio at the midsubstance was greater than at the femoral and tibial insertions in the ACL (p?=?0.00022 and 0.00025, respectively) and LCL (p?=?0.000081 and 0.000021, respectively) and was greater at the femoral insertion in the MCL (p?=?0.00010).

Conclusions: The mature collagen crosslink Pyr was not different in distribution in knee ligaments and the PT. Pen increased at the midsubstance ligaments and the PT. As increased Pen may represent ligament degeneration, this may indicate that degeneration may progress more rapidly at the midsubstance than at the insertion sites of a ligament.     

Receptors in the knee joint ligaments and their role in the biomechanics of the joint

The knee joint ligaments contain Ruffini, Pacinian, Golgi, and free-nerve endings with different capabilities of providing the CNS with information about movement and position as well as about noxious events. Skeletomotor neurons (alpha-motoneurons) are known to be influenced only very rarely and weakly from low-threshold mechanoreceptors in the ligaments, while the effects on the tau-muscle-spindle system in the muscles around the knee are so potent that even ligament stretches at very low loads may induce major changes in the responses of the muscle spindle afferents. Since the primary muscle spindle afferents participate in the regulation of muscular stiffness, the receptors in the knee joint ligaments probably contribute, via the tau-muscle-spindle system, to preparatory adjustment (pre-setting) of the stiffness of the muscles around the knee joint, and thereby to the joint stiffness and the functional joint stability.     

关节镜下LARS人工韧带与白体胭绳肌腱重建膝关节后交叉韧带早期疗效比较

目的 探讨先进韧带加强系统（LARS）人工韧带与自体四股胭绳肌腱（ST／G）重建后交叉韧带（PCL）手术的早期临床疗效。方法 回顾性分析徐州医学院附属医院骨科2008年7月-2013年5月收治的58例膝关节后韧带损伤患者的临床资料。其中LARS人工韧带重建PCL（LARS组）30例,两端均采用挤压螺钉固定;ST／G重建PCL（ST／G组）28例,股骨端使用Endobutton固定,胫骨端采取Intrafix挤压螺钉＋门型钉固定。采用Lysholm评分、Tegner评分、国际膝关节文献委员会（IKDC）评分对两组患者术前和术后3、6、9、12个月时患侧膝关节功能进行评分。结果 所有患者均顺利完成手术。均获随访12～18个月,平均14．5个月。LARS组患者术后扶拐下地、去拐行走、恢复轻量化运动时间[（12．4±4．3）h、（40．3±5．7）h、（3．4±0．6）h]均少于ST／G组[（23．5±6．6）h、（60．4±7．6）h、（7．2±1．3）h],差异均有统计学意义（t’=7．532、t=11．445、t’=14．127,P值均〈0．05）。LARS组在术后3、6、9个月时,Lysholm评分和IKDC评分均高于ST／G组,Tegner评分在术后3、6个月时高于ST／G组,差异均有统计学意义（P值均〈0．05）;在术后12个月时LARS组3种膝关节功能评分与ST／G组比较,差异均无统计学意义（P值均〉0．05）。结论 采用LARS人工韧带重建PCL具有手术创伤更小、术后恢复更快等优势,早期临床效果优于ST／G重建PCL手术;但远期临床效果需要进一步长期研究观察。     

Computational modeling of a forward lunge: towards a better understanding of the function of the cruciate ligaments

This study investigated the function of the cruciate ligaments during a forward lunge movement. The mechanical roles of the anterior and posterior cruciate ligament (ACL, PCL) during sagittal plane movements, such as forward lunging, are unclear. A forward lunge movement contains a knee joint flexion and extension that is controlled by the quadriceps muscle. The contraction of the quadriceps can cause anterior tibial translation, which may strain the ACL at knee joint positions close to full extension. However, recent findings suggest that it is the PCL rather than the ACL which is strained during forward lunging. Thus, the purpose of the present study was to establish a musculoskeletal model of the forward lunge to computationally investigate the complete mechanical force equilibrium of the tibia during the movement to examine the loading pattern of the cruciate ligaments. A healthy female was selected from a group of healthy subjects who all performed a forward lunge on a force platform, targeting a knee flexion angle of 90°. Skin-markers were placed on anatomical landmarks on the subject and the movement was recorded by five video cameras. The three-dimensional kinematic data describing the forward lunge movement were extracted and used to develop a biomechanical model of the lunge movement. The model comprised two legs including femur, crus, rigid foot segments and the pelvis. Each leg had 35 independent muscle units, which were recruited according to a minimum fatigue criterion. This approach allowed a full understanding of the mechanical equilibrium of the knee joint, which revealed that the PCL had an important stabilizing role in the forward lunge movement. In contrast, the ACL did not have any significant mechanical function during the lunge movement. Furthermore, the results showed that m. gluteus maximus may play a role as a knee stabilizer in addition to the hamstring muscles.     

Anterior intermeniscal ligament: an ultrastructural study.

The aim of the present study was to investigate the detailed histological characteristics of membranous and cord-like anterior intermeniscal ligaments (AIMLs) by transmission electron microscopy (TEM) and light microscopy. Ten biopsies of AIMLs were sampled from 10 knees during total knee arthroplasty procedures. Three of them were membranous and 7 of them were cord-like. They were processed for light and TEM evaluations. Histologically, the findings in the membranous and cord-like ligaments were similar. They consisted of parallel bundles of collagen fibrils and their posterior surfaces were covered by a layer of loose well-vascularized synovial tissue. The subsynovial region consisted of loose connective tissue and was rich in blood vessels and nerve endings. Fibroblasts embedded between parallel-oriented collagen fibrils were the major cell type that we observed. Free nerve endings were squeezed between bundles of collagen fibers. Electron microscopic observations revealed the presence of Ruffini corpuscles. The presence of neural mechanoreceptors in the membranous and cord-like intermeniscal ligaments may contribute to structural and proprioceptional function of the knee. Protection of those ligaments may be valuable in planning and performing meniscal surgeries.     

The multiple ligament-injured knee: When is primary repair an option?

BackgroundTreatment of multiple ligament-injured knees (MLIKs) remains complex and most often requires ligament reconstruction surgery. Reconstruction effectively restores knee stability but the procedure is invasive and can be complicated by stiffness or arthrofibrosis. There has been recent resurgence of interest in primary repair of knee ligaments. The goal was therefore to assess incidence of repairable ligaments in MLIKs, and determine patient and injury characteristics associated with potential for primary repair.MethodsA retrospective review of all MLIK patients surgically treated between 2009 and 2018 was conducted. All patients were treated with the same algorithm: primary repair was performed if the ligament was proximally or distally avulsed, and otherwise, reconstruction was performed. Patient characteristics, injury patterns, treatment specifics, and short-term outcomes were compared using independent t-tests and chi-square tests.ResultsForty-eight patients were included (mean age 32 years ± 14; 54% were male). Ultimately, 55% of ACL, 73% of PCL, 88% of MCL/PMC, and 87% of LCL/PLC injuries were repaired. Patients above 35 years (OR 6.9, P = 0.010) and higher BMI (OR 3.5, P = 0.046) were more likely to undergo ACL repair. No significant correlation was found in other ligaments. At a minimum of six-month follow-up (range 0.5–7.2 years), ACL repair failed in nine percent, PCL repair in 17%, MCL/PMC repair in 0%, and LCL/PLC repair in 18% of patients.ConclusionsThis study noted high incidences of repairable ligaments when MLIKs are treated within six weeks following injury. Although preliminary outcomes following primary repair in MLIK are good, further long-term follow-up studies are needed.     

Magnetic resonance imaging of the posterior cruciate ligament in flexion

Background

Posterior cruciate ligament (PCL) injuries of the knee are common and sometimes difficult to diagnose. Magnetic resonance imaging (MRI), performed using standard orthogonal plane views, is the investigation of choice. It can be particularly difficult to differentiate acute partial and complete tears and identify elongation of chronic healed tears. The aim of the paper is to describe a new method of positioning the patient with the knee flexed at 90°, allowing the PCL to be visualised in a position of greatest length and tension which may assist in differentiating and identifying these injuries.

Lateral collateral ligament and anterolateral ligament of the knee – A morphological analysis with orthopedic significance

BackgroundThe lateral collateral ligament (LCL) is the chief stabilizer of the lateral aspect of the knee to varus forces. Studies have confirmed the function of the anterolateral ligament (ALL), which improves the lateral knee stability by preventing excessive internal tibial rotation. Clinically, a persistent instability following anterior cruciate ligament reconstruction may be due to damage to the anterolateral structures. The finding has created a novel interest in anterolateral extra-articular operations.MethodsThis observational, cross-sectional study involved 42 dissected adult knees. The variations in morphology and morphometry of the LCL were identified and classified. The prevalence and the variabilities in the ALL were also noted.ResultsThe variations in the shape of the LCL were classified into four types: (1) cord, (2) band, (3) mixed, and (4) inverted Y shaped, with a frequency of 69.04, 26.20, 2.38, and 2.38% of specimens, respectively. The cord type measured 50.4 ± 2.7 mm in length and 5 ± 0.9 mm in width. In comparison, the band type measured 50.1 ± 4.2 mm in length and 9 ± 1.6 mm in width. The ALL was identified in four (9%) of the specimens with a mean length of 35 ± 0.9 mm. Two types of ALL were observed, membranous wideband and distinct cord-like ALL.ConclusionThe anatomy of the lateral structures of the knee is inconsistent. The study has attempted to classify the different shapes of the LCL along with the frequency and prevalence of the ALL. Orthopedic surgeons and radiologists must note the LCL morphology and prevalence of the ALL due to their clinical implications.     

Involvement of GDNF and its receptors in the maturation of the periodontal Ruffini endings

Our recent study revealed an intense immunoreaction for GDNF and its receptors in the Ruffini endings, primary mechanoreceptors in the periodontal ligament, of young rats. However, no information is available for the expression of GDNF and its receptors during their development. The present study aimed to reveal postnatal changes in the immuno-expression of GDNF, GFRalpha1 and RET in the periodontal Ruffini endings of the rat incisors by double immunofluorescent staining. At postnatal day 3 (PO 3d), no structure with GDNF-, GFRalpha1-, or RET-immunoreaction existed in the periodontal ligament. The PGP 9.5-positive nerve fibers without GDNF- and RET-immunoreaction displayed a dendritic fashion at PO 1w, with a GFRalpha1-reaction found around these nerves. At PO 2w, GDNF-positive terminal Schwann cells occurred near the thick and dendritic axons, a part of which showed a RET-reaction, with no reactive cells near the thin nerves. The terminal Schwann cells became positive for GFRalpha1, but lacked RET-immunoreaction. At PO 3w, when the formation of the periodontal Ruffini endings had proceeded, GDNF-positive terminal Schwann cells began to increase in number. This stage-specific immuno-expression pattern suggests that GDNF is a key molecule for the maturation and maintenance of the periodontal Ruffini endings.     

In-situ forces in the human posterior cruciate ligament in response to posterior tibial loading

Although some investigators have referred to the human posterior cruciate ligament (PCL) as the center of the knee, it has received less attention than the more frequently injured anterior cruciate ligament (ACL) and medial collateral ligament (MCL). Therefore, our understanding of the function of the PCL is limited. Our laboratory has developed a method of measuring thein-situ forces in a ligament without contacting that ligament by using a universal force-moment sensor (UFS). In this study, we attached a USF to the tibia and measuredin-situ forces of the human PCL as a function of knee flexion in response to tibial loading. At a 50-N posterior tibial load, the force in the PCL increased from 25±11 N (mean±SD) at 30° of knee flexion to 48±12 N at 90° of knee flexion. At 100 N, the corresponding increases were to 50±17 N and 95±17 N, respectively. Of note, at 30° knee flexion, approximately 45% of the resistance to posterior tibial loading was caused by contact between the tibia and the femoral condyles, whereas, at 90° of knee flexion, no resistance was caused by such contact. For direction of thein-situ force, the elevation angle from the tibial plateau was greater at 30° of knee flexion than at 90° of knee flexion. The data gathered on the magnitude and direction of thein-situ force of the PCL should help in our understanding of the dependence of knee flexion angle of the forces within the PCL.     

The ultrastructure of sensory nerve endings in the human knee joint capsule

Summary The ultrastructure of sensory nerve endings in the human knee joint capsule was studied. Three types of nerve endings were found: free nerve endings (FNE), Ruffini corpuscles and Pacini corpuscles.In the joint capsule, FNE are located below the synovial layer and within the fibrous layer near blood vessels. These nerve terminals derive from myelinated A-fibres or from unmyelinated C-fibres. Their structure is almost identical to FNE in human hairy and non-hairy skin.Ruffini corpuscles are present within the fibrous layer and the ligaments of the capsule in three variations: small Ruffini corpuscles without a capsule, small with a connective tissue capsule, and large Ruffini corpuscles with an incomplete perineural capsule. Their afferent axons are myelinated and measure 3–5 m in diameter. Inside the corpuscle, nerve terminals are anchored in the connective tissue belonging to the fibrous layer or to the ligaments respectively. The presence of an incomplete perineural capsule depends on the structure of the surrounding connective tissue. In ligaments with collagenous fibrils oriented in a parallel fashion, the perineural capsule is well-developed and the Ruffini corpuscle resembles a Golgi tendon organ; in areas where the fibrils show no predominant orientation, Ruffini corpuscles lack a capsule.Small Pacini corpuscles are situated within the fibrous layer near the capsular insertion at the meniscus articularis or at the periost. They consist of one or several inner cores and a perineural capsule of 1–2 layers. Larger Pacini corpuscles with one or several inner cores and a perineural capsule consisting of 20–30 layers are found on the outer surface of the fibrous layer.The ultrastructure of these nerve endings is compared with the ultrastructure of articular receptors of various animals and with the ultrastructure of sensory nerve endings in the skin of several mammalian species including man.Supported by the Verein zur Förderung der Erforschung und Bekämpfung rheumatischer Krankheiten e.V. in Bad Bramstedt andby the Deutsche Forschungsgemeinschaft (Sch 587/1-4)     

Vesicular Glutamate Transporter Immunoreactivity in the Periodontal Ligament of the Rat Incisor

The distribution of three vesicular glutamate transporter (VGluT) isoforms, VGluT1, VGluT2, and VGluT3, were investigated in the trigeminal ganglion of the periodontal ligament in the rat incisor—a receptive field of trigeminal ganglion neurons. In the trigeminal ganglion, mRNAs for all VGluT isoforms were detected and proteins were observed in the cytoplasm of trigeminal ganglion cells. VGluT1 immunoreactions were localized within the cytoplasm for all sizes of trigeminal neurons, although predominately in medium–large trigeminal neurons. Double‐labeling showed that most VGluT1 contained both VGluT2 and VGluT3. In the periodontal ligament of the incisor, the Ruffini endings, principal periodontal mechanoreceptors, displayed VGluT1 and VGluT2 immunoreactivities. However, lacked immunoreactions for VGluT3. At the electron microscopic level, VGluT1 immunoreactions were localized around the vesicle membranes at the axon terminal of Ruffini endings. The present results indicate that VGluT is expressed in the sensory nerve endings where apparent synapses are not present. Thus, glutamate in the sensory nerve endings is thought to be used in metabotropic functions. This is because glutamate is a general metabolic substrate, and/or acts as a neurotransmitter as proposed in muscle spindles. Anat Rec, 2012. © 2011 Wiley Periodicals, Inc.     

大收肌腱转位修复膝关节后交叉韧带的应用解剖及生物力学分析

目的以膝上内侧血管为蒂大收肌腱转位重建膝关节后交叉韧带断裂缺损,比较重建前后的生物力学差异。方法36例经动脉灌注红色乳胶成人标本,解剖观测大收肌腱的形态及其血供,模拟手术设计,以膝上内侧血管为蒂大收肌腱转位修复膝关节后韧带断裂缺损,并比较在修复前后,在屈膝0^o、30^o、60^o、90^o和120^o时胫骨后移距离和韧带应变。结果后交叉韧带断裂后胫骨的负荷后移明显加大,重建后向正常时回归,移植物的生物力学变化的总体趋势与正常时相似。结论采用大收肌腱重建膝关节后PCL,可以取得较满意的重交叉韧带,在各屈膝角度均能有效防止胫骨后移,生物力学特征更接近于正常建效果。     

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

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 (Aδ) or C fibres with diameters of 1–2 μm. 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 μm) 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 μm, 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. Anat Rec 254:13–21, 1999. © 1999 Wiley‐Liss, Inc.     

Graft position at the femoral condyle affects knee mobility after posterior cruciate ligament replacement

BackgroundIn some cases posterior cruciate ligament (PCL) tears require surgical reconstruction. As the femoral footprint of the ligament is quite large, an ideal graft fixation position on the medial notch wall has not yet been identified. The aim of this study was to compare three different graft fixation positions within the anatomical footprint of the PCL and test it for posterior tibial translation at different knee flexion angles.MethodsIn six human knee specimens a drawer test was simulated on a material testing machine by applying load on the tibia. At three different knee flexion angles (0°, 45°, 90°) knee mobility was examined with respect to tibial posterior translation and stiffness for the following conditions: intact ligaments, detached PCL, three different graft fixation positions on the femoral condyle.ResultsReplacement of the PCL within its femoral footprint restored knee stability in terms of tibial posterior translation. Low graft position showed comparable drawer displacements to the intact condition for all knee flexion angles (p > 0.344). A higher graft position excessively reduced the posterior translation (p < 0.047) and resulted in a restricted knee mobility and a stiffer joint.ConclusionsGraft fixation positions on the femoral condyle play a crucial role in post-operative knee mobility and joint functionality after PCL replacement. Even though all graft fixation positions were placed within the femoral footprint of a native PCL, only the lower position on the medial notch wall showed comparable posterior tibial translation to an intact PCL.     

Sensory innervation of the cat knee articular capsule and cruciate ligament visualised using anterogradely transported wheat germ agglutinin–horseradish peroxidase

Wheat germ agglutinin–horseradish peroxidase conjugate (WGA–HRP) was injected into the dorsal root ganglia (L5–S1) of the cat and used as an anterograde tracer substance for intra-axonal labelling of peripheral nerve endings in joint capsule and cranial (anterior) cruciate ligament (CCL). We believed that the high specificity of WGA–HRP for neural tissue along with the high visibility of its reaction product could help resolve controversies concerning the sensory innervation of the cruciate ligaments. Substantial amounts of WGA–HRP were transported in tibial nerve axons to the level of the knee. However, using standard HRP histochemistry we found that the capsular tissue and ligament synovia disintegrated during the incubation reaction. This problem was avoided by air drying the tissue slices on glass slides prior to reaction. Abundant labelling occurred in the posterior capsule with dense filling of axons and terminal endings. Sensory endings displayed features consistent with Ruffini endings and pacinian corpuscles. Sensory endings were located throughout the CCL in its sagittal plane, in the subsynovial layers and between collagen fascicles. In each CCL we observed 5–17 ovoid and elongated endings with dense terminal arborisations. These endings were between 100 and 150 μm long, were encapsulated, and gave rise to 1 or 2 axons. Large (up to 1.5 mm in maximum extent) elongated regions of dense, inhomogeneous labelling were found in the body of several CCLs. These resembled Golgi tendon-like endings, with the exception of their large size. We conclude that anterograde transport of HRP to the knee is a useful technique for labelling mechanoreceptors and axons in knee tissue. However, recently developed immunohistochemical analysis of peripheral tissue using protein gene product 9.5 appears to be the method of choice and should be employed for further study of human and animal cruciate ligament innervation.     

The posterior meniscofemoral ligament: morphologic study and anatomic classification

The meniscofemoral ligaments (MFLs) run from the medial femoral condyle to the posterior horn of the lateral meniscus and consist of anterior MFL (aMFL) and/or posterior MFL (pMFL) components according to whether it passes anterior or posterior to the posterior cruciate ligament (PCL). The purpose of this study was to analyze the incidence and morphologic features of the MFLs in Koreans and formulate an anatomic classification system of MFLs to aid the detailed interpretation of medical imaging or biomechanical data. One hundred knees from 52 cadavers were studied. Eighty-seven knees had pMFLs, whereas an aMFL was only found in one knee from a male cadaver. The pMFLs and PCLs were longer in males than in females (P < 0.05). The most common type of MFL was the high crossing of a typical pMFL against the PCL in both genders. Regarding other types, the incidence of absent pMFLs was higher in males than in females and the oblique bundle of the PCL was easily confused with the pMFL in several cases in both genders. These results provide the basis for the classification system of the MFL and will contribute to better outcomes for evaluating the MFL and PCL when using medical imaging such as arthro-CT scan or MRI through a better understanding of the anatomy of the MFL and PCL.     

Anatomical study of the lateral collateral ligament and its circumference structures in the human knee joint

Thirty-six cadavers (55 sides) were used to observe the innervation of the lateral collateral ligament (LCL) and its circumference structures with gross anatomical and histological methods to clarify the cause of indistinct pain in the lateral part of the knee joint. The innervating branches of the LCL could be divided into three types: (1) from the muscular branch of the biceps femoris muscle at lower 1/3 level of the thigh; (2) from the common fibular nerve (CFN) at the higher level of the fossa poplitea; (3) from the CFN at the level of the caput fibular. Furthermore, the three branches could singly or plurally distribute to the LCL (six types). Two of the connecting tissue membranes surrounding the surface of LCL formed an incomplete sheath structure, and a shutting “gap” was observed between the two membranes. Fine peripheral nervous branches were also observed in the two of the membranes. On the other hand, three types of nerve endings in the LCL (Type Ι/Ruffini mechanoreceptor; Type ΙΙΙ/Golgi mechanoreceptor; Type ΙV/free nerve ending) were observed, and their presence was consistent with the ankle joint of humans. Therefore, the innervation of the two membranes (to form the shutting gap) in the surface of LCL may be associated with an indistinct pain when the knee joint is damaged.     

Distribution of sensory nerve endings around the human sinus tarsi: a cadaver study

The aim of this study was to analyse the pattern of sensory nerve endings and blood vessels around the sinus tarsi. The superficial and deep parts of the fat pads at the inferior extensor retinaculum (IER) as well as the subtalar joint capsule inside the sinus tarsi from 13 cadaver feet were dissected. The distribution of the sensory nerve endings and blood vessels were analysed in the resected specimens as the number per cm² after staining with haematoxylin‐eosin, S100 protein, low‐affinity neurotrophin receptor p75, and protein gene product 9.5 using the classification of Freeman and Wyke. Free nerve endings were the predominant sensory ending (P < 0.001). Ruffini and Golgi‐like endings were rarely found and no Pacini corpuscles were seen. Significantly more free nerve endings (P < 0.001) and blood vessels (P = 0.01) were observed in the subtalar joint capsule than in the superficial part of the fat pad at the IER. The deep part of the fat pad at the IER had significantly more blood vessels than the superficial part of the fat pad at the IER (P = 0.012). Significantly more blood vessels than free nerve endings were seen in all three groups (P < 0.001). No significant differences in distribution were seen in terms of right or left side, except for free nerve endings in the superficial part of the fat pad at the IER (P = 0.003). A greater number of free nerve endings correlated with a greater number of blood vessels. The presence of sensory nerve endings between individual fat cells supports the hypothesis that the fat pad has a proprioceptive role monitoring changes and that it is a source of pain in sinus tarsi syndrome due to the abundance of free nerve endings.