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The posterior cruciate ligament (PCL) represents an intra-articular structure composed of two distinct bundles. Considering the anterior and posterior meniscofemoral ligaments, a total of four ligamentous fibre bundles of the posterior knee complex act synergistically to restrain posterior and rotatory tibial loads. Injury mechanisms associated with high-energy trauma and accompanying injury patterns may complicate the diagnostic evaluation and accuracy. Therefore, a thorough and systematic diagnostic workup is necessary to assess the severity of the PCL injury and to initiate an appropriate treatment approach. Since structural damage to the PCL occurs in more than one third of trauma patients experiencing acute knee injury with hemarthrosis, background knowledge for management of PCL injuries is important. In Part 1 of the evidence-based update on management of primary and recurrent PCL injuries, the anatomical, biomechanical, and diagnostic principles are presented. This paper aims to convey the anatomical and biomechanical knowledge needed for accurate diagnosis to facilitate subsequent decision-making in the treatment of PCL injuries. Level of evidence V.

Background Magnetic resonance imaging (MRI) is a reliable diagnostic tool for anterior cruciate ligament (ACL) injuries. Nonetheless, the clinical relevance of morphological changes in the posterior cruciate ligament (PCL), such as the M-shaped PCL, following ACL injuries has not been well studied. This study aimed to investigate whether the presence of M-shaped PCL was associated with meniscal and ligamentous injuries in patients with ACL injuries. Methods From May 2018 to May 2023, a total of 281 patients diagnosed noncontact ACL injuries with arthroscopy were retrospectively reviewed. The preoperative MRI images were examined to identify the presence of M-shaped PCL. Thirty-five patients with an M-shaped PCL were included in the study group, while 70 patients with non-M-shaped PCL were matched using 1:2 ratio by age (within 2 years) and sex to the control group. Key anatomical factors of the femur and tibia, including femoral notch width (NW), bicondylar width (BCW), notch width index (NWI), medial tibial depth (MTD), static anterior tibial subluxation (SATS), medial tibial slope (MTS), lateral tibial slope (LTS), as well as the status of meniscal and ligamentous injuries including medial and lateral menisci (LM), medial and lateral collateral ligaments, and anterolateral ligament (ALL) were assessed using MRI. The Spearman correlation coefficients and multivariate logistic regression were applied to analyze potential predictors of M-shaped PCL. Results The mean age of all patients was 34.7 ± 10.2 years, and the male-to-female ratio was 3:4 in each group. The incidence of M-shaped PCL was 12.4%. The study group demonstrated a higher proportion of ALL injuries compared to the control group (54.3% vs 31.4%, respectively; p  = 0.024). In all patients, the presence of M-shaped PCL independently predicted ALL injury ( p  = 0.021). In the M-shaped PCL group, ALL injury was associated with NW ( ρ  = 0.372; p  = 0.028), BCW ( ρ  = 0.380; p  = 0.024), and SATS ( ρ  = 0.437; p  = 0.009). Additionally, LM lesions ( p  = 0.041), a larger NW ( p  = 0.038), and SATS ( p  = 0.019) independently predicted ALL injury. In the non-M-shaped PCL group, LTS was correlated with ALL injury ( ρ  = 0.375; p  = 0.001), and a larger LTS independently predicted ALL injury ( p  = 0.005). Conclusion In patients with ACL injuries, the presence of an M-shaped PCL was associated with ALL injury. For patients with M-shaped PCL, ALL injury was associated with LM lesions, a larger NW, and SATS.

This paper focuses on the anatomical attachment of the medial meniscus. Detailed anatomical dissections have been performed and illustrated. Five zones can be distinguished in regard to the meniscus attachments anatomy: zone 1 (of the anterior root), zone 2 (anteromedial zone), zone 3 (the medial zone), zone 4 (the posterior zone) and the zone 5 (of the posterior root). The understanding of the meniscal anatomy is especially crucial for meniscus repair but also for correct fixation of the anterior and posterior horn of the medial meniscus.

Purpose This study aimed to assess the posterior cruciate ligament (PCL) angle in anterior cruciate ligament (ACL) deficient knees and correlate it with anatomical and demographic factors such as tibial slope, anterior tibial translation, age, gender, and time of injury. Material and methods Patients were eligible for inclusion if they were clinically diagnosed with an ACL tear confirmed by MRI. For each patient, the following parameters were evaluated: PCL angle (PCLA), medial tibial slope (MTS), lateral tibial slope (LTS), medial anterior tibial translation (MATT), and lateral anterior tibial translation (LATT). Results A total of 193 patients were included in the study, comprising 91 (47.2%) females and 102 (52.8%) males, with a mean age of 30.27 ± 12.54 years. The mean time from injury to MRI was 14.18 ± 55.77 days. In the overall population, the mean PCL angle was 128.72 ± 10.33°, the mean medial tibial slope was 3.57 ± 2.33°, and the mean lateral tibial slope was 6.07 ± 3.52°. The mean medial and lateral anterior tibial translations were 4.76 ± 2.02 mm and 7.01 ± 2.48 mm, respectively. In 190 cases (98.4%), the PCL angle was ≥ 105°. The PCL angle negatively correlated with medial and lateral anterior tibial translation ( p  < 0.05). Females exhibited a higher PCL angle compared to males ( p  = 0.019). Conclusion In the context of ACL lesions, the PCL angle has a normal value in acute injuries (> 105°) and decreases over time. The PCL angle is negatively correlated with anterior tibial translation, and females have a higher PCL angle compared to males. Level of evidence IV Retrospective Cohort.

PurposeThe medial synovial fold of the posterior cruciate ligament is one of the synovial plicae of the knee joint. The objective of this study was to assess the necessity of reporting the appearance of the medial synovial fold of the posterior cruciate ligament on magnetic resonance imaging of the knee joint and its correlation with side and sex.MethodsPatients with normal knee structure on magnetic resonance imaging (MRI) scans between 2018 and 2023 were included in this retrospective study. MRI scans of the knee joints were retrospectively reviewed by two musculoskeletal radiologists independently. The medial synovial fold of the posterior cruciate ligament was divided into three types according to the imaginary line drawn between the lateral border of the medial femoral condyle and the medial tibial intercondylar tubercle.ResultsThe study included 1147 patients, of whom 478 (41.7%) were female and 669 (58.3%) were male. Among these patients, 580 (50.6%) had a right knee scan, and 567 (49.4%) had a left knee scan. The age range was 15–35 years for both sexes. The frequency of the medial synovial fold types in all patients was as follows: Type A (30.1%), Type B (55.4%) and Type C (14.5%). There was a high level of agreement between the observers. There was a statistically significant difference in the frequency of medial synovial fold types between sexes, with men exhibiting a greater prevalence.ConclusionMagnetic resonance imaging (MRI) of the knee joint revealed the medial synovial folds of the posterior cruciate ligament (PCL). The most common was Type B (55.4%), followed by Type A (30.1%) and Type C (14.5%) among the MSF types. No statistically significant difference was found between the right and left knees for any of the MSF types.

Background The killer turn has been documented as the primary drawback of posterior cruciate ligament (PCL) reconstruction. Fanelli advocated placing the tibial tunnel outlet in the inferior lateral part of the PCL fovea to reduce the killer turn. This study aimed to confirm the validity of Fanelli’s viewpoint regarding PCL reconstruction technique and to assess the specific Fanelli tunnel area on the inferior lateral part of the PCL fovea. Methods The geometrical data of the model were obtained by nuclear magnetic resonance (MRI) and computerized tomography (CT), with images taken from a healthy Chinese volunteer. The three-dimensional finite element model of the knee joint was established using Mimics, Geomagic Studio, 3-matic, and Ansys software. The finite analysis was performed after the material behavior, contact and boundary conditions, and loading were defined. The drawer tests were simulated with a posterior tibial load of 134 N at 0°, 30°, 60°, and 90° knee flexion. The PCL peak stress and tibial translation were recorded and compared among the 30 distinct tibial tunnel loci over a range of angles from 0° to 90°. Results In the area (Fanelli area, 5–20 mm inferior and 5–10 mm lateral to the PCL anatomical insertion), the lowest PCL peak stress in all sites with different flexion angles was lower than that of the PCL anatomical insertion site. The lowest PCL peak stress with different knee flexion angles was observed in the following location: 10 mm inferior and 5 mm lateral to the PCL anatomical insertion. In the Fanelli area, the tibial translations of three sites were lower and those of other sites were higher than that of the PCL anatomical insertion site. Conclusions PCL reconstruction in the Fanelli area, especially 10 mm inferior and 5 mm lateral to the PCL anatomical insertion, could reduce the peak stress of the graft and may reduce the killer turn. However, whether the posterior stability of the knee is affected needs to be further studied.

The posterior cruciate ligament (PCL) is the strongest ligament of the knee, serving as one of the major passive stabilizers of the tibio-femoral joint. However, despite a number of experimental and modelling approaches to understand the kinematics and kinetics of the ligament, the normal loading conditions of the PCL and its functional bundles are still controversially discussed. This study aimed to generate science-based evidence for understanding the functional loading of the PCL, including the anterolateral and posteromedial bundles, in the healthy knee joint through systematic review and statistical analysis of the literature. MEDLINE, EMBASE and CENTRAL. Databases were searched for articles containing any numerical strain or force data on the healthy PCL and its functional bundles. Studied activities were as follows: passive flexion, flexion under 100N and 134N posterior tibial load, walking, stair ascent and descent, body-weight squatting and forward lunge. Statistical analysis was performed on the reported load data, which was weighted according to the number of knees tested to extract average strain and force trends of the PCL and identify deviations from the norms. From the 3577 articles retrieved by the initial electronic search, only 66 met all inclusion criteria. The results obtained by aggregating data reported in the eligible studies indicate that the loading patterns of the PCL vary with activity type, knee flexion angle, but importantly also the technique used for assessment. Moreover, different fibres of the PCL exhibit different strain patterns during knee flexion, with higher strain magnitudes reported in the anterolateral bundle. While during passive flexion the posteromedial bundle is either lax or very slightly elongated, it experiences higher strain levels during forward lunge and has a synergetic relationship with the anterolateral bundle. The strain patterns obtained for virtual fibres that connect the origin and insertion of the bundles in a straight line show similar trends to those of the real bundles but with different magnitudes. This review represents what is now the best available understanding of the biomechanics of the PCL, and may help to improve programs for injury prevention, diagnosis methods as well as reconstruction and rehabilitation techniques.

Purpose To evaluate the safety for neurovascular structures and accuracy for tunnel placement of the posterolateral portal tibial tunnel drilling technique in posterior cruciate ligament (PCL) reconstruction. Methods Fifteen fresh-frozen human cadaveric knees were used. The tibial tunnel for the PCL was created using a flexible reamer from the posterolateral portal. Then, the flexible pin was left in place, and the distance from the posterolateral portal, the flexible pin, and the tibial tunnel to the peroneal nerve and popliteal artery was measured. Additionally, the distance between the tibial tunnel and several landmarks related to the PCL footprint was measured, along with the distance from the exit point of the flexible pin to the superficial medial collateral ligament and gracilis tendon. Results The peroneal nerve and the popliteal neurovascular bundle were not damaged in any of the specimens. The median (range) distance in mm from the peroneal nerve and popliteal artery to the posterolateral portal and flexible pin was: 52 (40–80) and 50 (40–61), and 35 (26–51) and 22 (16–32), respectively. The median (range) distance from the tibial tunnel to the popliteal artery was 21 mm (15–38). The tibial tunnel was located at a median (range) distance in mm of 3 (2–6), 6 (3–12), 5 (2–7), 4 (1–8), 9 (3–10), 10 (4–19), and 19 (6–24) to the champagne-glass drop-off, lateral cartilage point, shiny white fibre point, medial groove, medial meniscus posterior root, lateral meniscus posterior root, and posterior aspect of the anterior cruciate ligament, respectively. Conclusions The posterolateral portal tibial tunnel technique is safe relative to neurovascular structures and creates an anatomically appropriate tibial tunnel location. The clinical relevance of study is that this technique may be safely and accurately used in PCL reconstruction to decrease the risk of neurovascular damage (avoid use of a posteriorly directed pin), avoid the use of intraoperative fluoroscopy, and avoid the sharp turn during graft passage.

PurposeTo analyze whether preoperative patellofemoral anatomy is associated with clinical improvement and failure rate after isolated patellofemoral arthroplasty (PFA) using a modern inlay-type trochlear implant.MethodsProspectively collected 24 months data of patients treated with isolated inlay PFA (HemiCAP® Wave, Arthrosurface, Franklin, MA, USA) between 2009 and 2016, and available digitalized preoperative imaging (plain radiographs in three planes and MRI) were retrospectively analyzed. All patients were evaluated using the WOMAC score, Lysholm score, and VAS pain. Patients revised to TKA or not achieving the minimal clinically important difference (MCID) for the total WOMAC score or VAS pain were considered failures. Preoperative imaging was analyzed regarding the following aspects: Tibiofemoral OA, patellofemoral OA, trochlear dysplasia (Dejour classification), patellar height (Insall–Salvati index [ISI]; Patellotrochlear index [PTI]), and position of the tibial tuberosity (TT–TG and TT–PCL distance).ResultsA total of 41 patients (61% female) with a mean age of 48 ± 13 years could be included. Fifteen patients (37%) were considered failures, with 5 patients (12%) revised to TKA and 10 patients (24%) not achieving MCID for WOMAC total or VAS pain. Failures had a significantly higher ISI, and a significantly lower PTI. Furthermore, the proportion of patients with a pathologic ISI (> 1.2), a pathologic PTI (< 0.28), and without trochlear dysplasia were significantly higher in failures. Significantly greater improvements in clinical outcome scores were observed in patients with a higher preoperative grade of patellofemoral OA, ISI ≤ 1.2, PTI ≥ 0.28, TT–PCL distance ≤ 21 mm, and a dysplastic trochlea.ConclusionPreoperative patellofemoral anatomy is significantly associated with clinical improvement and failure rate after isolated inlay PFA. Less improvement and a higher failure rate must be expected in patients with patella alta (ISI > 1.2 and PTI < 0.28), absence of trochlear dysplasia, and a lateralized position of the tibial tuberosity (TT–PCL distance > 21 mm). Concomitant procedures such as tibial tuberosity transfer may, therefore, be considered in such patients.Level of evidenceLevel III, retrospective analysis of prospectively collected data.

This paper describes the anatomy of the posterior cruciate ligament (PCL) and the meniscofemoral ligaments (MFLs). The fibres of the PCL may be split into two functional bundles; the anterolateral bundle (ALB) and the posteromedial bundle (PMB), relating to their femoral attachments. The tibial attachment is relatively compact, with the ALB anterior to the PLB. These bundles are not isometric: the ALB is tightest in the mid‐arc of knee flexion, the PMB is tight at both extension and deep flexion. At least one MFL is present in 93% of knees. On the femur, the anterior MFL attaches distal to the PCL, close to the articular cartilage; the posterior MFL attaches proximal to the PCL. They both attach distally to the posterior horn of the lateral meniscus. Their slanting orientation allows the MFLs to resist tibial posterior drawer.