PurposeThe purpose of the present study was to determine how the medial structures and ACL contribute to restraining anteromedial instability of the knee. Methods Twenty-eight paired, fresh-frozen human cadaveric knees were tested in a six-degree of freedom robotic setup. After sequentially cutting the dMCL, sMCL, POL and ACL in four diferent cutting orders, the following simulated clinical laxity tests were applied at 0°, 30°, 60° and 90° of knee lexion: 4 Nm external tibial rotation (ER), 4 Nm internal tibial rotation (IR), 8 Nm valgus rotation (VR) and anteromedial rotation (AMR)-combined 89 N anterior tibial translation and 4 Nm ER. Knee kinematics were recorded in the intact state and after each cut using an optical tracking system. Diferences in medial compartment translation (AMT) and tibial rotation (AMR, ER, IR, VR) from the intact state were then analyzed. ResultsThe sMCL was the most important restraint to AMR, ER and VR at all lexion angles. Release of the proximal tibial attachment of the sMCL caused no signiicant increase in laxity if the distal sMCL attachment remained intact. The dMCL was a minor restraint to AMT and ER. The POL controlled IR and was a minor restraint to AMT and ER near extension. The ACL contributed with the sMCL in restraining AMT and was a secondary restraint to ER and VR in the MCL deicient knee. ConclusionThe sMCL appears to be the most important restraint to anteromedial instability; the dMCL and POL play more minor roles. Based on the present data a new classiication of anteromedial instability is proposed, which may support clinical examination and treatment decision. In higher grades of anteromedial instability an injury to the sMCL should be suspected and addressed if treated surgically.

Traditional bone-patellar tendon-bone and hamstring tendon ACL grafts are not without limitations. A growing body of anatomic, biomechanical and clinical data has demonstrated the utility of quadriceps tendon autograft in arthroscopic knee ligament reconstruction. The quadriceps tendon autograft provides a robust volume of tissue that can be reliably harvested, mitigating the likelihood of variably sized grafts and obviating the necessity of allograft augmentation. Modern, minimally invasive harvest techniques offer the advantages of low rates of donor site morbidity and residual extensor mechanism strength deficits. New data suggest that quadriceps tendon autograft may possess superior biomechanical characteristics when compared with bone-patella tendon-bone (BPTB) autograft. However, there have been very few direct, prospective comparisons between the clinical outcomes associated with quadriceps tendon autograft and other autograft options (eg, hamstring tendon and bone-patellar tendon-bone). Nevertheless, quadriceps tendon autograft should be one of the primary options in any knee surgeon's armamentarium.

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Background: Complications and the need for revision surgery after medial patellofemoral ligament reconstruction (MPFLR) are evident in the current literature. However, there is a shortage of clinical data evaluating the results of revision surgery in individual patients after failed MPFLR. Purpose: To investigate the results of tailored revision surgery for failed MPFLR, including the correction of predisposing factors. Study Design: Cohort study; Level of evidence, 3. Methods: Between August 2015 and March 2019, 25 patients (male:female, n = 9:16; mean ± SD age, 25.9 ± 6.5 years) underwent revision surgery for failed MPFLR (study group). The Banff Patella Instability Instrument 2.0 (BPII 2.0) and a numerical analog scale (0-10) for patellofemoral pain and subjective knee joint function were used to assess patient-reported quality of life before and after revision surgery. The control group of 50 patients (male:female, n = 18:32; age, 22.8 ± 4.3 years) who underwent identical patellar-stabilizing procedures was matched 1:2 by the surgical procedure, predisposing factors, sex, age, and follow-up time. Results: Evaluation was performed postoperatively at a mean 27.8 ± 14.0 months (range, 12-54 months) in the study group and 26.1 ± 11.2 months (range, 12-56 months) in the control group ( P = .55). The BPII 2.0 score increased from 28.6 ± 17.9 points to 68.7 ± 22.3 points ( P < .0001) in the study group and from 43.8 ± 22.5 points to 75.5 ± 21.4 points ( P < .0001) in the control group from preoperatively to postoperatively, respectively. Before revision surgery, the BPII 2.0 scores in the study group were significantly inferior to those in the control group ( P = .0026). At the final follow-up, the BPII 2.0 score in the study group was not significantly lower ( P = .174), and a similar number of patients in the study group and the control group achieved the minimally clinically important difference ( P = .49). Patellofemoral pain and subjective knee joint function improved significantly in both groups ( P < .0001, P < .0001), without any significant difference between them at the final follow-up ( P = .85, P = .86). Conclusion: Revision surgery for MPFLR failure, including the correction of major anatomic risk factors, yielded a significant improvement in patient-reported quality-of-life outcome measures. Patients with failed MPFLR, however, were significantly more restricted before revision surgery than patients without previous interventions when evaluated with the BPII 2.0.

Purpose To determine which risk factors for patellar instability contribute most relevantly to patients' subjective diseasespeciic quality of life, aiming to provide implications on the overall treatment decision-making process. Methods A total of 182 consecutive patients (male/female 70/112; mean age 23.6 ± 7.3 years) with a history of patellar instability were prospectively enrolled in this study. Patient age, body mass index (BMI), number of dislocations, reversed dynamic patellar apprehension test (ReDPAT), J-sign severity, and pathoanatomic risk factors of patellar instability were assessed. The statistical analysis evaluated the relationships among those variables and determined their ability to predict the Banf Patellofemoral Instability Instrument 2.0 (BPII 2.0) as a disease-speciic quality of life measure. Using Spearman correlation, ANOVA and Fisher's exact test, all variables with ANOVA p ≤ 0.1 or Spearman's abs (rho) > 0.1 were entered into a multivariate linear model using backward-stepwise selection. Results Analysis of the individual variables' ability to predict BPII 2.0 score values revealed 'age', 'BMI', 'ReDPAT', 'high grade of trochlear dysplasia', and 'high-grade J-Sign' as possible relevant factors. Backward-stepwise multivariate regression analysis yielded a inal parsimonious model that included the factors 'BMI' and 'J-Sign (Grade II and III)' as the most relevant parameters inluencing BPII 2.0 score values (adjusted R 2 = 0.418; p < 0.001), with a cutof value for BMI found at 28 kg/m 2 (p = 0.01). ConclusionThe results of this study indicate that in patients with lateral patellar instability, a high-grade J-sign and an increased BMI signiicantly impact subjective disease-speciic quality of life. Level of evidence Level IV.