Pain Management in TKA: Periarticular Injections and Peripheral Nerve Blocks

    Most multimodal pain control regimens for total knee arthroplasty patients include a combination of oral medications, periarticular injection of anesthetics and/or analgesics, and selective motor-sparing nerve blocks. What is the evidence for this approach?


    Alexander Gaukhman, MD; Simon Garceau, MD; Ran Schwarzkopf, MD, MSc; and James Slover, MD, MS


    Strategies for pain control following total knee arthroplasty (TKA) have significantly evolved over the last 3 decades: [1]

    • The 1980s saw a rise in the use of intramuscular injections of narcotics.
    • In the 1990s, the patient-controlled analgesia pump was often the modality of choice for managing postoperative pain.
    • By the 2000s, surgeons had shifted toward protocols that minimized the use of opioids, driven in part by early rehabilitation protocols and faster discharge from the hospital.

    Today, most multimodal pain control regimens include a combination of oral medications, periarticular injection (PAI) of anesthetics and/or analgesics, and selective motor-sparing nerve blocks. [1]

    Pros and Cons of Peripheral Nerve Blocks

    Peripheral nerve blocks (PNB) are commonly used in TKA for adjunctive analgesia. Sensory innervation of the knee originates anteriorly from the femoral nerve and posteriorly from the posterior cutaneous nerve of the thigh emanating from the sciatic nerve. In addition, variable contributions from the saphenous nerve and the lateral femoral cutaneous nerve provide sensory innervation to the medial and lateral aspects of the knee, respectively. [1,2] These nerves and their respective tributaries are common targets for peripheral nerve blockade.

    The use of PNBs has the purported benefit of: [3-5]

    • Reduced hospital length of stay (LOS)
    • Earlier participation in postoperative physical therapy
    • Decreased opioid consumption, as well as fewer side effects associated with these drugs

    Compared with epidural anesthesia, the use of PNBs has been observed to reduce the risk of postoperative hypotension and urinary retention. [6]

    Femoral nerve blocks (FNB) have historically been the mainstay of PNBs performed for TKAs, [2] providing motor and sensory blockade through diffusion of local anesthetic to the femoral, lateral femoral cutaneous, and obturator nerves. The term “3-in-1 block” has been coined to describe FNBs. The resultant anesthetic effect is localized to the anterior, lateral, and medial aspects of the knee.

    Overall, FNBs offer excellent analgesia, especially when combined with a sciatic nerve block (SNB). [7,8] Compared with epidural anesthesia, FNBs have been found to provide a similar analgesic effect, greater patient satisfaction, and reduced postoperative nausea and vomiting. [9]

    The motor blockade associated with FNBs, however, leads to profound quadriceps weakness, [10,11] which has been associated with a slower postoperative rehabilitation process and an estimated 7% risk of falls. [11] Sharma et al [12] reported a 0.4% risk of reoperation secondary to falls in the postoperative period in patients who had received an FNB. When an SNB is utilized in conjunction with an FNB, the anesthetic effect to the heel can put patients at risk for pressure ulcers if precautionary measures are not ensured during the postoperative period. [13-14]

    Adductor canal blocks (ACB) are performed under ultrasound guidance and affect the peripheral nerves within the adductor canal: the saphenous nerve, articular branches of the obturator nerve, medial retinacular nerve, and nerve to vastus medialis. [2] The use of ACBs has gained popularity, especially with the push toward outpatient TKA, as they provide good analgesic effect to the anteromedial aspect of the knee with minimal motor blockade. [10]

    In a randomized, double-blind, placebo-controlled study, Jaeger et al [10] compared quadriceps weakness in healthy volunteers who received either an ACB or an FNB using ropivacaine. They noted an 8% versus 49% reduction in quadriceps strength, respectively, up to 6 hours after surgery, as well as a reduction in early postoperative visual analog scale (VAS) scores and opioid consumption in the ACB group. [10] Early mobility at 1 and 6 hours post-blockade was improved in the ACB group compared with the FNB group. [10]

    However, similar to FNBs, ACBs do not provide analgesia to the posterior capsule of the knee. Therefore, a combination of an ACB and PAI is often employed to supplement deficiencies in analgesic coverage. Although this combination is intuitively logical, study results have been mixed, [15] likely related to significant variation in PAI technique and location. [16] Infiltration between the popliteal artery and the capsule of the knee (IPACK) has demonstrated promising early results in providing additional targeted analgesia to the posterior aspect of the knee. [17-19]

    Periarticular Injections: Where and What to Inject

    Nerve sensation to the knee is, in part, provided by the femoral, saphenous, obturator, common peroneal, and tibial nerves. The current literature suggests that 45% to 80% of nerve fibers in the knee are nociceptors. [20] Numerous studies have investigated nociceptor anatomic distribution in the knee. In a histologic survey of 8 human cadaveric knees, Biedert et al [21] sought to identify nociceptor density within the various structures of the knee. They found the highest concentrations in the medial and lateral retinacula, patellar tendon, pes anserinus, and meniscofemoral ligaments. [21] Other studies have identified the capsule and periosteum as a pain generator. [22]

    The pharmacology of PAI cocktails has been studied extensively. Injections are usually a mixture of a long-acting anesthetic, non-steroidal anti-inflammatory drugs, and epinephrine as a base. The addition of corticosteroids has had variable results. Chia et al [23] randomized patients to receive either a conventional cocktail without corticosteroids or cocktails containing various dosages of corticosteroids. They noted no difference among groups.

    Kulkarni et al, [24] however, demonstrated a reduction in VAS scores at 24 and 72 hours after surgery with the addition of methylprednisolone to PAI in patients undergoing TKA. They also noted an increase in postoperative flexion and an increase in inflammatory signs in patients who received corticosteroid infiltration. [24]

    The addition of morphine to PAIs has also been studied. Iwakiri et al [25] randomized patients to receive periarticular cocktails with or without morphine. They found similar VAS scores between groups, but an increase in the number of vomiting episodes and the total dose of antiemetic drugs in patients who had received morphine. [25]

    Liposomal bupivacaine was initially approved for use in surgical wounds to provide postoperative analgesia. The efficacy of liposomal bupivacaine over traditional bupivacaine in periarticular injection has yet to be proven due to differences in study design, methodology, and infiltration techniques, among others.

    The PILLAR study has attempted to reconcile confounding variables that may have contributed to inconsistent results, randomizing 2 sets of patients undergoing TKA to receive standard bupivacaine versus liposomal bupivacaine. [26] Using robust statistics, the study authors were able to show a significant improvement in pain control among patient receiving the liposomal bupivacaine cocktail.

    However, a large systematic review and meta-analysis failed to show a true clinical benefit for the use of liposomal bupivacaine in either PAIs or PNBs. [27]

    Peripheral Nerve Blocks versus Periarticular Injection

    As mentioned above, ACBs have become more popular due to equivalent pain control and decreased motor blockade when compared with FNBs. [1] Periarticular injections are also being used more frequently as part of a multimodal pain control strategy. [1] Is one more effective than the other in managing postoperative pain following TKA?

    In a study by Grosso et al, [28] patients were randomized to receive ACB alone, PAI alone, or ACB plus PAI. Patients who received ACB alone had higher pain scores and increased opioid consumption compared with patients who received PAI alone or PAI plus ACB. The latter 2 groups had equivalent pain scores. [28]

    Similar outcomes have been noted in the anesthesia literature. Sawhney et al [29] randomized patients to the same interventions as Grosso et al, [28] with similar results: Patients receiving an ACB alone had greater pain scores than patients in the other 2 intervention groups.


    With the ongoing opioid crisis in the US, the orthopaedic community has a strong impetus to provide opioid-sparing analgesia to surgical patients. The result has been an emphasis on administering care in the context of multimodal pain control, with PAIs and PNBs being key elements in many protocols. These modalities play an important role in the mitigation of postoperative pain in TKA patients, with the ideal therapy providing robust analgesia with minimal risk of adverse events and allowing for early engagement in postoperative rehabilitation. Current evidence suggests that an ACB supplemented by a PAI or IPACK for posterior capsular analgesic coverage may provide optimal results.

    Author Information

    Alexander Gaukhman, MD; Simon Garceau, MD; Ran Schwarzkopf, MD, MSc; and James Slover, MD, MS, are from the Division of Orthopedics, Adult Joint Reconstruction, at NYU Langone Health, New York, New York.

    Disclosures: Dr. Gaukhman, Dr. Garceau, and Dr. Schwarzkopf have no disclosures relevant to this article. Dr. Slover has disclosed that he is a paid consultant for Horizon Pharma.


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