Adding steroid to local anaesthetics in local infiltration analgesia reduced inflammation both locally and systemically, resulting in significant early pain relief and rapid recovery in total knee arthroplasty.

Up-regulation of nociceptive markers in subchondral bone afferents correlated with subchondral bone damage, suggesting that subchondral bone is a therapeutic target, especially in the case of advanced stage knee OA. In particular, CGRP and TrkA are potentially molecular therapeutic targets to treat joint pain associated with subchondral lesions.

Background The subchondral bone of the distal femur is a source of pain caused by osteoarthritis (OA) or spontaneous osteonecrosis of the knee. However, nociceptive phenotype of dorsal root ganglia (DRG) neurons innervating the subchondral bone in rat knee joints has not been clarified. Methods Retrograde labelling was used to identify afferents innervating the subchondral bone of the distal femur and the knee joint in rats. The nociceptive phenotype markers [calcitonin gene‐related peptide (CGRP), tyrosine receptor kinase A (TrkA), neurofilament 200 (NF200) and isolectin B4 (IB4)], segmental distribution and the soma size of backlabelled DRG neurons were examined. Furthermore, we evaluated the differences in nociceptive phenotype between the subchondral bone and the knee joint afferents. Results The majority (60%) of the subchondral bone afferents were localized in L3 DRGs and fewer in L4 and L5, while the knee joint afferents were localized mainly in L3 and L4. The percentage of CGRP immunoreactive (IR), TrkA‐IR, NF200‐IR and IB4‐binding neurons in the subchondral bone afferents were 50%, 65%, 35% and 0%, respectively. The percentage of CGRP‐IR and TrkA‐IR neurons in the subchondral bone afferents was significantly higher than that in the knee joint afferents, respectively (p < 0.05). Conclusion The majority of sensory DRG neurons innervating the subchondral bone of the distal femur were CGRP‐IR and TrkA‐IR. It is expected that therapeutic approaches targeting CGRP and TrkA could be effective in attenuating pain from the subchondral bone in knee joints.

Randomized controlled trial, Level I.

Although larger studies are needed to examine its safety, the local infusion analgesia alone provided clinically significant analgesic effects and rapid recovery in total knee arthroplasty.

Intra-articular HA injections reduced the severity of OA, decreased mechanical hyperalgesia of the paw, but not weight-bearing asymmetry, and attenuated OA-associated up-regulation of CGRP, but not TrkA and ASIC3, in joint afferents. The modulatory effects of HA on joint afferents is one of the underlying mechanisms of the gap between HA residence time and duration of clinical efficacy.

PurposeAlthough disease progression of osteoarthritis has been well documented, pain pathophysiology is largely unknown. This study was designed with two purposes: 1) to characterize patients with knee pain predominantly originating from intra-articular structures and 2) to describe the location and pattern of their pain.Materials and methods103 patients with medial knee osteoarthritis underwent an intra-articular injection of local anesthetics (joint block). At least 70% pain relief was defined as positive for the joint block, while less than 50% as negative. Pain characteristics in patients positive for joint block were evaluated in detail using a knee pain map.ResultsSixty three knees (61%) were positive and 33 knees (32%) were negative. Patients negative for the joint block were significantly higher age, suffered for longer time, and complained more diffuse pain. Although pain at anterior medial area during walk was the most common finding, pain characteristics differed among different knee areas.ConclusionThe characteristics of joint pain are widely variable even in patients with similar radiological features. Extra-articular sources are not negligible especially in older patients with a long history of diffuse pain. Differences in pain characteristics among knee areas should be taken into account when examining the pain source.

Purpose Multimodal analgesia has become an important concept in current pain management following total knee arthroplasty (TKA). However, controversy remains over what is the most accepted combination. In this study, the additional benefits of local infiltration of analgesia to femoral nerve block were evaluated. Methods Forty patients were randomly allocated into a combined local infiltration of analgesia and femoral nerve block or femoral nerve block alone group. In the former, analgesic drugs consisting of ropivacaine and dexamethasone were injected into the peri‐articular tissues, while the same amount of saline was injected into the femoral nerve block group. The primary outcome measure was the total amount of fentanyl consumption by the patient‐controlled analgesia pump during the 48‐h post‐operative period. Results A combination of local infiltration of analgesia and femoral nerve block had less total fentanyl consumption and a larger knee ROM at post‐operative day 2 than femoral nerve block alone (p < 0.05). C‐reactive protein levels in the combined treatment group were significantly lower than the femoral nerve block group at post‐operative day 3 (p < 0.01). There was no difference between the two groups, post‐operatively, on the visual analogue scale for pain at rest or while walking, quadriceps strength, timed up and go test, circumference of thigh, Knee Society Score, and Western Ontario and McMaster Universities Osteoarthritis Index. Conclusion The addition of local infiltration of analgesia to femoral nerve block promoted post‐operative pain relief and the recovery of knee ROM in the early post‐operative period. This combination is an effective method for post‐operative pain management after TKA. Level of evidence Randomized controlled trial, Level I.