The Anatomy And Imaging Observations And Clinical Application Of The Knee Synovium And Related Structure

Objective: The synovial pathological changes and effusion of knee joint is a very common disease at present. Because of the complicated structure of the knee joint and the different clinical symptoms shown by the synovial pathological changes and effusion, clinical diagnoses and treatment could be very difficult. According to the anatomy of knee synovial, the present study aimed to explore the anatomical basis of Synovial capsule formation and investigate the characteristics of Synovial pathological changes of knee joint. Different volume of contrast-medium was injected into the cavity of fresh normal adult knee joints. The joints were observed by MRI scanning. The results were intended to provide objective evidence and quantitative standards for clinical diagnosis of knee joints effusion with different volumes.Methods:(1) Model specimens'construction: red latex suspension was injected into the femoral artery of 20 adult fresh lower limbs. 1:1 denture powder and water mixture was injected into the joint cavity and the deep infrapatellar. After fillers solidification, the models were placed into 30% hydrochloric acid solution and corroded.(2) Morphology observation: 30 knee joints of cadaver specimens were anatomized to observe the synovial morphology of the suprapatellar bursa, the deep infrapatellar bursa, the superior border of patella-cartilage, the post-wall crypt, the deep infrapatellar bursa and knee joint cavity. Tissue was drawn from these parts to observe.(3) Specimens and living object measurement: 20 knee specimens were measured to observe morphological changes in flexion and extension position in the deep infrapatellar bursa. Located by the patella and tibial tuberosity lower edge, 20 volunteers were measured the length of patellar tendon connected at the lower edge of the patella and the tibial tuberosity in flexion and extension movement.(4) Effusion volume measurement: 1, 5, 10, 15, 20, 30, 40(ml) contrast-medium was injected into the cavity of 10 normal-structured adult knee joint specimens with no effusion or pneumatosis respectively. The knee joints were observed by MRI scanning in coronal section, vertical plane and transect with T2WI in the thickness of 4mm and distance of 1mm.ResultsCharacteristics of deep infrapatellar bursa:There are the similar synovial tissues in the inside surfaces of knee joint cavity and deep infrapatellar bursa. The synovial of deep infrapatellar bursa does not sequentially generate by the knee joint cavity. The area between knee joint cavity and deep infrapatellar bursa was filled and separated by adipose tissue. This area of knee joint cavity and deep infrapatellar bursa was connected by descending genicular artery, inferior-internal arteries, superior-external artery, inferior-external arteries and their branches. According to the body measurements with the knee extension position, the length of patellar deep sac was 0.9cm ~ 1.1cm with the maximum width of 0.5cm. The length of patellar ligament is 4.5cm ~ 4.8cm. With the position of 45°flexion of the knee joint, the patellar deep capsule's widest part is 0.6cm with the height of 0.4cm ~ 0.6cm. In vivo measurement of knee extension bits, the distance between the lower edge of the patella and tibial tuberosity is 4.5cm ~ 4.8cm. With the flexion of 145°, the height is 9.0cm ~ 9.5cm.The morphologic characteristics of synovial: 26 of the 30 specimens present synovial hardening at the superior border of patella-cartilage, accounting for 87% of the whole group. 22 of the 30 specimens (73%) present synovial thickness more than 5mm at the suprapatellar bursal. And 21 of the 30 specimens (70%) present synovial roughness in the deep infrapatellar bursal. Each index of the rest parts has shown significant deviation (p<0.001). On the superior border of patella-cartilage and post-wall crypt, hyperplasia incidences of synovial cells and small vessels were 80 %( 24 out of 30) and 57 %( 17 out of 30). Interstitial fibrosis and hyalinization was 83 %( 25 out of 30) and 74 %( 22 out of 30), which significantly differed from other parts (p<0.001).Measurement of effusion volume:①MRI scanning of coronal section: after 10 ml contrast-medium injection in the center of medial knee joint, high visual signal was seen in the cavity of joint.②MRI scanning at the distance of 1.5 cm from internal vertical plane of middle knee: after 5 ml contrast-medium injection, high visual signal area appeared in intercondylar eminence and narrowed gradually. High visual signal area appeared in 70% of posterosuperior internal condyle of tibia;③MRI scanning of inframarginal Apex of patella of knee transect: after 5 mL contrast-medium injection, high visual signal appeared in 90% area at 1/3 point posterior articular cavity; after more than 10 mL contrast-medium injection, high visual signal was seen in 70% area of anterior thighbone facet.Conclusion:The synovial tissue between knee joint cavity and deep infrapatellar bursa is separated. Patellar tendon friction is one of the causes for the formation of synovial. Changes usually happen in the Synovial membrane at the deep infrapatellar bursa,suprapatellar bursa,and superior border of patella. The histological variation was often found in the superior border of patella-cartilage and post-wall crypt.By injecting different volumes of contrast-medium into the knee cavity and peripheral synovial bursa, reference standard can be constructed according to different volumes of effusion, which is significantly beneficial for diagnosis of effusion in the knee cavity and peripheral synovial bursa with MRI scanning.