Flexibility of infrapatellar fat pad affecting anterior knee pain 6 months after anterior cruciate ligament reconstruction with hamstring autograft

The thickness change ratio and preservation ratio of the infrapatellar fat pad are related to anterior knee pain in patients following medial patellofemoral ligament reconstruction

BACKGROUND

The infrapatellar fat pad (IPFP) lies extrasynovial and intracapsular, preserving the joint cavity and serving as a biochemical regulator of inflammatory reactions. However, there is a lack of research on the relationship between anterior knee pain (AKP) and the IPFP after medial patellofemoral ligament reconstruction (MPFLR). Pinpointing the source of pain enables clinicians to promptly manage and intervene, facilitating personalized rehabilitation and improving patient prognosis.

METHODS

A total of 181 patients were included in the study. These patients were divided into the AKP group (n = 37) and the control group (n = 144). Clinical outcomes included three pain-related scores, Tegner activity score, patient satisfaction, etc. Imaging outcomes included the IPFP thickness, IPFP fibrosis, and the IPFP thickness change and preservation ratio. Multivariate analysis was used to determine the independent factors associated with AKP. Finally, the correlation between independent factors and three pain-related scores was analyzed to verify the results.

RESULTS

The control group had better postoperative pain-related scores and Tegner activity score than the AKP group (P < 0.01). The AKP group had lower IPFP thickness change ratio and preservation ratio (P < 0.001), and smaller IPFP thickness (P < 0.05). The multivariate analysis revealed that the IPFP thickness change ratio [OR = 0.895, P < 0.001] and the IPFP preservation ratio [OR = 0.389, P < 0.001] were independent factors related to AKP, with a significant correlation between these factors and pain-related scores [|r| > 0.50, P < 0.01].

CONCLUSIONS

This study showed the lower IPFP change ratio and preservation ratio may be independent factors associated with AKP after MPFLR. Early detection and targeted intervention of the underlying pain sources can pave the way for tailored rehabilitation programs and improved surgical outcomes. LEVEL OF EVIDENCE LEVEL III.

Outcome analysis of infrapatellar fat pad partial resection or preservation in patients with anterior cruciate ligament reconstruction

The infrapatellar fat pad (IPFP) is one of the structures surrounding the knee joint that obscures exposure in minimally arthroscopy anterior cruciate ligament reconstruction (ACLR). Most surgeons excise the partial fat pad for better exposure of the knee. However, whether removal of IPFP in ACLR remained inconclusive. The purpose of this study was to investigate clinical outcomes of IPFP preservation or resection in patients with primary hamstring-graft ACLR. A total of 104 patients were assigned to receive either IPFP-R (n = 55) or IPFP-P (n = 49). There were no significant preoperative differences between the two groups. The anterior knee pain (AKP) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) in the two groups both recovered compared with those at baseline, but the IPFP-P group recovered more significantly at 3-, 6-, 12-month, and 3-, 6-month of follow-up, respectively. When assessing the KOOS subclasses using minimum perceptible clinical improvement (MPCI), patients with IPFP-R failed to make significant improvement at 3 months in the symptoms, pain and sports subsets of the KOOS. Knee-related complications were not significantly different between the two groups, while the resection group had a higher incidence. These results suggested that ACLR with primary hamstring grafts can achieve good effects whether performed with IPFP resection or preservation; however, the improvements in anterior knee pain and knee joint functions are better for the patients with IPFP preservation. Therefore, surgeons should avoid the resection of IPFP as much as possible while fully exposing the wild view to ensure the ACLR.

Relationship between the change in infrapatellar fat pad thickness assessed using ultrasonography and anterior knee pain on squatting after anterior cruciate ligament reconstruction

PURPOSE

Anterior knee pain (AKP) may occur after anterior cruciate ligament (ACL) reconstruction. The present study investigated the relationship between the change in infrapatellar fat pad (IFP) thickness assessed using ultrasonography (US) and AKP on squatting in patients after ACL reconstruction.

METHODS

Patients were enrolled 3 months after ACL reconstruction using the bone-tendon-bone (BTB) technique. Subjects were divided into the AKP group (numerical rating scale [NRS] score ≥ 1) and control group (NRS score < 1) using a NRS of pain on squatting, and intergroup comparisons were performed. On US evaluation, measurement angles of the knee joint were 0° and 30° in the supine position. The IFP between the femoral intercondylar notch and patellar tendon was measured on short-axis images. The changes in IFP thickness were calculated from values measured at different angles of the knee joint.

RESULTS

Twenty-one patients (mean age 24.9 ± 9.3 years) were included in the present study: 12 in the AKP group (9 males, 3 females) and nine in the control group (5 males, 4 females). A significant difference in the change in IFP thickness at 3 months was observed between the AKP and control groups (0.67 ± 0.44 mm vs. 1.84 ± 0.34 mm, p < 0.001). There was a negative correlation between the change in IFP thickness and the NRS score (r = - 0.720, p < 0.001) in reconstructed knees.

CONCLUSION

A smaller change in IFP thickness assessed using US after ACL reconstruction was identified as a factor contributing to AKP on squatting.

Consequences of anterior knee pain after anterior cruciate ligament reconstruction: A 2015-2020 cohort study

Anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) graft aims to stabilise the knee, but it may bring some complications like anterior knee (AKP) pain that can have consequences on the functional aspect of this surgery. The aim of this study was to compare isokinetic knee strength and functional outcomes between patients with and without AKP following an ACLR using HT graft during the first-year post-surgery. Three hundred and thirty subjects operated by ACLR using hamstring tendon graft were included in our retrospective cohort and divided into two groups: a group with AKP (AKP+ group) and one without AKP (AKP-group). In our population, 14.8% of the patients had AKP. At 4 post-operative months, subjects with pain had lower isokinetic strength limb symmetry index (LSI) for knee flexors and extensors, and a lower Lysholm score than subjects without pain (p < 0.0001). These differences did not persist at 7 post-operative months, and there was no difference in the one-leg hop test. After multivariate analysis, we highlighted the impact of time on the evolution of these parameters. Yet, the exact definition of AKP after ACLR remains to be clearly defined since an imprecise diagnosis may lead to inappropriate management. Pre-operative information about this type of complication, which evolves favourably with time, could be useful for patients. Indeed, AKP can occur after ACLR, even if a HT graft has been used, compared to other surgical procedures using the knee extensor apparatus as patellar tendon graft (AKP is associated with the donor site morbidity). In case of AKP after ACLR, monitoring the muscle inhibition by isokinetic tests may enable clinicians to adapt the retraining and the return to sport.

Effect of physical therapy on the flexibility of the infrapatellar fat pad: A single-blind randomised controlled trial

The infrapatellar fat pad plays a biomechanical role in the knee joint. After knee injury or surgery, its dynamics decrease because of an inflammatory response. Physical therapy might be one of the valuable treatments for the recovery of knee joint mobility. This study aimed to evaluate the immediate effect of physical therapy on the dynamics of the infrapatellar fat pad in healthy participants using ultrasonography. In this prospective, single-blind, randomised controlled trial, 64 healthy young participants were enrolled and randomly assigned to one of the following three interventions: manual therapy, hot pack treatment, and control. Ultrasound images of the infrapatellar fat pad were obtained before and after the intervention. The thickness change ratio of the infrapatellar fat pad was calculated to compare the changes between and within groups before and after the intervention. No significant inter-group differences were observed. The effect sizes were relatively small. Manual therapy or hot pack intervention might not have an immediate effect on infrapatellar fat pad flexibility in healthy participants. Thus, it is necessary to consider more intensive treatments to change the dynamics of the infrapatellar fat pad.

Ultrasound Imaging of the Anterior Cruciate Ligament: A Pictorial Essay and Narrative Review

Ultrasound has been extensively applied to the diagnosis of and guided interventions for knee disorders. However, although it is commonly affected during sports injuries, the anterior cruciate ligament (ACL) is not usually incorporated in the majority of ultrasound scanning protocols. In the past, because of its oblique trajectory and deeper location, the ACL was considered to be a challenging structure for ultrasound imaging. Owing to advances in ultrasound technology and knowledge of knee sono-anatomy, an increasing number of studies are investigating the clinical value of ultrasound in the diagnosis and management of ACL injuries. In this regard, the present review aims to elaborate on the sono-anatomy of the ACL, to summarize the evidence for ultrasound imaging for ACL lesions and to investigate whether it is useful in the pre-operative preparation and post-operative follow-up of ACL reconstruction.