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Bone bruise patterns are commonly seen after acute anterior cruciate ligament injuries; they represent a subchondral impaction injury that occurs in the lateral knee joint between the mid-lateral femoral condyle and the posterior lateral tibial plateau. These contusion patterns are present in the majority of noncontact ACL injuries. These injury patterns vary significantly in severity and this aspect is poorly understood. Edema patterns have gained increased interest in the literature of late; they may indicate the severity of the initial injury. They also may be correlated with the development of subsequent osteochondral defects and osteoarthritis. Given the location of this subchondral injury, it is plausible to assume that the geometry of the lateral femorotibial joint may play a role in ACL injury mechanism and severity of injury. We are reporting two cases of clinically identical ACL injuries. A patient with a flat lateral tibial plateau was noted to have a much larger bone edema pattern than a second patient with the highly convex lateral tibial plateau. This may shed light on the pathomechanics of ACL injury and suggests that an individual with a relatively flat tibial plateau has a stable lateral knee joint. Therefore, we hypothesize that much greater force is required to dislocate a flat and stable lateral femorotibial joint in a pivot shift pattern to produce an ACL injury. The greater force required results in a large bone edema pattern. Conversely, the individual with a relatively short and convex tibial plateau has an inherently unstable lateral joint and relatively smaller amounts of force would be needed to produce the identical injury to the ACL. As less force is required, smaller bone edema patterns result.

Background: Lateral tibiofemoral articular geometry may play a role in the development of non-contact anterior cruciate ligament (ACL) injuries. We hypothesized that athletes who had sustained an ACL injury would demonstrate more highly convex articular surfaces in the lateral compartment of the knee compared with activity-matched athletes who had not sustained an ACL injury, and that women would demonstrate greater absolute and relative convexity of these articular surfaces than men., Methods: One hundred and twelve athletes with a non-contact ACL injury and sixty-one activity-matched athletes without an ACL injury were studied. Three blinded observers measured the articular geometry in the mid-lateral sagittal plane with use of magnetic resonance imaging. The tibial plateau radius of curvature (TPr), distal femoral radius of curvature (Fr), maximal femoral anteroposterior articular length (FAP), and maximal tibial anteroposterior articular length (TPAP) were recorded. The Fr:TPr and FAP:TPAP ratios were also calculated to adjust for size variations. The intraclass correlation coefficient and the two-sample Student t test were used to compare quantitative variables. All data were found to follow a normal distribution., Results: When data for male and female patients were combined, the mean TPr, Fr, and TPAP values were significantly smaller in the ACL-injured patients than in the uninjured patients (33.9 compared with 37.5 mm, p = 0.005; 24.3 compared with 25.1 mm, p = 0.04; and 31.5 compared with 33.1 mm, p = 0.007; respectively). The mean FAP value did not differ significantly between the ACL-injured and uninjured patients but the difference in the mean FAP:TPAP value was significant (p = 0.003). When only male patients were analyzed, the mean TPr, Fr, and TPAP values were also significantly smaller in the ACL-injured patients than in the uninjured patients (35.5 compared with 41.1 mm, p = 0.002; 25.5 compared with 26.7 mm, p = 0.001; and 33.0 compared with 35.5 mm, p = 0.0002; respectively). The mean FAP value did not differ significantly between the ACL-injured and uninjured male patients, but the difference in the mean FAP:TPAP value was significant (p = 0.0005). In contrast, when only female patients were analyzed, none of the mean values differed significantly between the ACL-injured and uninjured patients. The FAP:TPAP and Fr:TPr values did not differ significantly among the ACL-injured male patients, injured female patients, and uninjured female patients., Conclusions: All female patients (both ACL-injured and uninjured) and ACL-injured male patients shared a common lateral knee geometry characterized by a smaller tibial plateau length relative to the femur and by more convex articulating surfaces of the proximal aspect of the tibia and the distal aspect of the femur. Shorter, more highly convex articulating surfaces may be inherently less stable with regard to anterior tibial translation and rotation. These findings may partially explain the greater overall predisposition of women compared with men toward ACL injury as well as why some studies have demonstrated no sex differences in graft reinjury after ACL reconstruction.

Background: Previous studies indicate that isolated posterior cruciate ligament injuries demonstrate magnetic resonance imaging (MRI) and clinical evidence of healing when treated nonoperatively; however, the authors are unaware of any other study that has looked at whether initial MRI can predict posterior cruciate ligament stability at the time of surgery in patients with knee dislocation.Hypothesis: An MRI grading system will predict laxity on posterior drawer testing at the time of surgery in patients with knee dislocations.Study Design: Cohort study (prognosis); Level of evidence, 2.Methods: Forty-two consecutive patients with knee dislocation or multiple-ligament knee injury evaluated by MRI were included in the study. An assignment of grade 0 (intact), grade I (injured/fibers intact), grade II (partial tearing of ligament), or grade III (complete tear) was made after each reading on 2 separate occasions by 3 surgeons. Posterior laxity of the knee was graded by the magnitude of excursion on the posterior drawer test by the senior author at the time of surgery. Interobserver and intraobserver reliability of the MRI grading scheme expressed by the kappa statistic κ, as well as the predictive value of MRI grade in determining stability of the posterior cruciate ligament at the time of surgery, was assessed.Results: The posterior cruciate ligament injury grading scheme tested demonstrated moderate to substantial intraobserver agreement (κ = 0.66, κ = 0.53, and κ = 0.52, respectively, for all raters). Interobserver reliability demonstrated only moderate agreement (κ = 0.49). If the grading scheme was changed to group both grades 0 and I (intact) and grades II and III (disrupted), intraobserver reliability demonstrated substantial to almost perfect agreement (κ = 0.83, κ = 0.80, and κ = 0.75), and interobserver reliability demonstrated substantial agreement (κ = 0.70). If the posterior cruciate ligament was classified as intact (grade 0 [intact] or grade I [injured]) on initial MRI, the injured knee was judged clinically stable (tibia anterior to or flush with the femoral condyles on posterior drawer testing) at the time of surgery 98.5% (95% confidence interval, 93%-100%) of the time. When the posterior cruciate ligament was classified as disrupted (grade II [partial tear] or grade III [complete tear]), the injured knee was judged unstable (tibia posterior to the femoral condyles on posterior drawer testing) 57.5% (95% confidence interval, 40%-73%) of the time.Conclusion: The presented system of grading posterior cruciate ligament injury in patients with knee dislocation on initial MRI demonstrates moderate to substantial interobserver and intraobserver reliability that increases if the grading scheme is modified. An initial MRI scan read as grade I may predict stability to posterior drawer at the time of surgery. Even with MRI evidence of disruption in the posterior cruciate ligament (grade II and grade III injuries), posterior cruciate ligament reconstruction may not be clinically indicated at the time of reconstruction and/or repair of other associated injuries. [ABSTRACT FROM AUTHOR]

A concerning number of patients referred to our clinic with knee dislocations have not been thoroughly evaluated for popliteal injury. The objective of this study is to present our experience and attempt to identify possible causes for this trend. Thirty-one consecutive patients with knee dislocations referred over a 1-year period were evaluated. Patients were assigned to either of two groups: Group I included all patients initially evaluated with an evidence-based protocol for identifying clinically significant vascular injury associated with knee dislocation, and Group II included all patients who had not received an evidence-based evaluation. The main outcome measure was delay in the diagnosis of a limb threatening vascular injury (>8 h) within each group. Six out of the 31 patients referred, were evaluated for vascular injury without an evidence-based protocol. These patients were significantly more likely to have had a delay in the diagnosis of their vascular injury beyond 8 h ( P = 0.032) and were less likely to have been evaluated at a level I trauma center ( P < 0.001). As expected, evidence-based protocols are superior when compared to initial pedal pulse examination alone for identifying surgically significant vascular injury within 8 h. The consequences of a delay in diagnosis beyond 8 h can be catastrophic and one patient in this series required an above-knee amputation. This is not new information, however, a significant number of patients with knee dislocations continue to be evaluated solely by initial pedal pulse examination. Though effective protocols exist, orthopedic surgeons must work to facilitate the implementation of these protocols at their referring institutions. [ABSTRACT FROM AUTHOR]