**2.2 Menisci**

These are thick pads of fibrocartilaginous crescent-shaped plates found between the articular surfaces of the femur and tibia. By deepening the articular surface, they increase joint stability; and by increasing surface area to dissipate forces further, they act as a shock absorber during weight-bearing and joint movements.

They are highly vascular and thicker in the outer one-third than the inner two-third [5]. The outer one-third contains larger circumferentially arranged bundles whereas, the inner two-thirds contain radially organized collagen bundles. This makes the outer portion of the menisci suitable for resisting tensional forces and the inner portion for adaptation for weight-bearing. The anterior horn of both the menisci attaches to the anterior tibial intercondylar area and blends with ACL. The posterior horn of both the menisci attaches to the posterior tibial intercondylar area. The lateral meniscus is more mobile and smaller than the medial meniscus. The menisci are held in place by other ligaments like transverse ligament, meniscofemoral ligaments, meniscotibial (coronary) ligaments, and patellomeniscal ligament (medial and lateral). All these ligaments indirectly prevent displacement of the knee joint. Surgical removal of the meniscus can lead to osteoarthritic changes in the underlying cartilage.

#### **2.3 Bursae**

A bursa is a tiny, slippery, fluid-filled sac located between a bone and soft tissue to reduce friction between them. Arthritis of the knee joint leads to alteration into the joint biomechanics leading to irritation of the bursa. This irritation leads to inflammation called bursitis. Among various types of bursae around the knee, the notable bursae include [6],


#### **2.4 Muscles around the knee**

The muscle groups attached to the knee joint provide strong support and keep the joint stable, well-aligned, and moving. These groups include,


The four movements (**Table 1**) that occur at the knee joint are flexion, extension, lateral and medial rotation. With the flexed knee joint, the lateral and medial rotations occur at the hip joint and vise versa. The hamstrings are responsible for both the hip extension and knee flexion. The knee flexion ranges from 120 degrees to 140 degrees (with the extended hip), increasing 160 degrees with the passive flexion [7, 8].

*Regional Analgesia for Knee Surgeries: Thinking beyond Borders DOI: http://dx.doi.org/10.5772/intechopen.99282*


**Table 1.**

*Muscles responsible for various movements in the knee joint.*

## **2.5 Neurovascular supply**

The knee joint has a rich vascularization from the genicular anastomosis around the knee (**Figure 1**) formed by genicular branches from femoral and popliteal arteries [9]. There are approximately ten arteries involved in the formation of genicular anastomosis:


The nerve supply of the knee joint follows Hilton's law, as innervations of the muscles which cross joints also innervate the knee joint. The knee joint receives all its

**Figure 1.** *Genicular anastomosis around the knee joint.*

innervation from the branches of the lumbar and sacral plexus. The knee joint innervations need detailed considerations before planning procedure-specific RA techniques.
