**11.4 Postoperative pain generators**

The postoperative pain of any surgery depends on the number of pain generators removed and retained after surgery (**Figure 18**). The TKR surgery involves removing many pain generators (like anterior capsule, synovium, meniscus,

#### **Figure 18.**

*Preoperative and postoperative pain generating structures of knee surgeries. Yellow colored area in circles: Anterior knee innervations. Blue colored area in circles: Posterior knee innervations. Red star-like dots: Pain generating area. TKR: Total knee replacement.*

#### **Figure 19.**

*Analgesic coverage of various regional techniques for knee surgeries. Green colored area in circles: Analgesic covered regions. (FTB: Femoral triangle block, ACB: Adductor canal block, DSB: Dual subsartorial block, IPACK: Ilfiltration between popliteal artery and capsule of knee joint, LIA: Local infiltration analgesia).*

cruciates, intraarticular ligaments, periosteum of the knee joint, and prepatellar fat pads) [11, 72–77]. The retained pain-generating components responsible for post-TKR pain include skin/subcutaneous tissues over the incision area, medial retinaculum, periosteal rim of the cut bones, remnant of the anterior joint capsule, cut nerves along the surgical dissection area, microfractures, and inflammation. For arthroscopic knee surgery, the pain-generating components are mainly intraarticular. Therefore, the innervations of these retained components are essential targets for any procedure-specific RA techniques.

The analgesic coverage of each RA technique is different, as shown in **Figure 19**. The choice of RA techniques depends on the procedure performed and its associated innervations.

An "identify-select-combine" approach [78, 79] is beneficial to obtain procedurespecific RA techniques for knee surgery (**Table 5**). This approach includes identifying target innervations, selecting target blocks involving most of the target nerves, and combining all target blocks to cover innervations of all the pain generators.

#### **12. Conclusion**

Background knowledge of the knee joint and its components is essential to achieve the best surgical and analgesic outcomes. Perioperative pain management of the patient undergoing any knee surgery is a complex and challenging task. Therefore, the holistic approach is required considering the patient's age, comorbid

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


*(FNB: Femoral nerve block, LFCN: Lateral femoral cutaneous nerve, FTB: Femoral triangle block, ACB: Adductor canal block, DSB: Dual subsartorial block, SCN: Sciatic nerve, i-PACK: Ilfiltration between popliteal artery and capsule of knee joint, LIA: Local infiltration analgesia)*

#### **Table 5.**

*Procedure-specific regional analgesia options for knee.*

factors, psychological components, complex innervations, multifactorial pain generations, surgery type, and demand for the best analgesic options suitable for ERAS protocol.

Optimum perioperative analgesia reduces the stress response of the surgery or pain. It hastens early mobilization and discharge, reduces hospital stay and associated complications, controls treatment costs, most importantly, improves patient satisfaction. A well-functioning knee joint is essential to improve quality of life and reduce perioperative morbidity and mortality. Multimodal analgesia for multifactorial pain should be the ideal protocol for knee surgeries. The regional analgesia, an essential component of MMA, should be motor-sparing, opioid-sparing, and procedure-specific.
