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Background: Trochlear dysplasia is a known risk factor for patellar instability. Multiple radiographic measurements exist to assess trochlear morphology, but the optimal measurement technique and threshold for instability are unknown. Purpose: To describe the optimal measurements and thresholds for trochlear dysplasia on magnetic resonance imaging (MRI) that can identify knees with patellar instability in male and female patients. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Knee MRI scans of patients with patellar instability were compared with those of age- and sex-matched controls. Measurements of the sulcus angle, lateral trochlear inclination (LTI), and trochlear depth were performed on axial images using bony and cartilaginous landmarks. Receiver operating characteristic curve analysis was performed, with the area under the curve (AUC) describing the accuracy of each diagnostic test. Optimal cutoff values were calculated to distinguish between knees with and without patellar instability. AUC and cutoff values were reported for each measurement as well as for male and female subgroups. Results: A total of 238 knee MRI scans were included in this study (138 female, 100 male; age range, 18-39 years). Trochlear depth measurements had the greatest diagnostic value, with AUCs of 0.79 and 0.82 on bone and cartilage, respectively. All measurements (sulcus angle, LTI, trochlear depth) on bone and cartilage had an AUC ≥0.7 (range, 0.70-0.86), with optimal cutoff values of 145° (bone) and 154° (cartilage) for the sulcus angle, 17° (bone) and 13° (cartilage) for LTI, and 4 mm (bone) and 3 mm (cartilage) for trochlear depth. Optimal cutoff values in female patients varied from those in male patients for all measurements except for cartilaginous trochlear depth. Conclusion: Normal thresholds for trochlear dysplasia varied based on the use of bony versus cartilaginous landmarks. Cartilaginous trochlear depth measurements had the greatest ability to identify knees with patellar instability. Furthermore, optimal cutoff values for all measurements except for cartilaginous trochlear depth differed between female and male patients. These findings suggest that sex-specific parameters of normal values may be needed in the assessment of risk factors for patellofemoral instability.

PURPOSE OF REVIEW: To discuss the treatment options and rehabilitation protocols after non-operative and operative treatment of patellar instability, and to discuss expected return to play outcomes and functional performance with non-operative and operative treatment of patellar instability. RECENT FINDINGS: A criterion-based program assessing range of motion, joint effusion, strength, neuromuscular control, proprioception, agility, and power are critical measures to assess when rehabilitating this population. A series of functional tests including quadriceps strength testing, single-limb hop testing, lateral step-down test, the side hop test, the lateral leap and catch test, the Y-balance test, and the depth jump should be considered when determining an athlete’s return to sport clearance. These objective measures combined with psychological readiness and a comprehensive understanding of the sports-specific tasks required for participation should be considered when evaluating an athlete’s ability to safely and successfully return to sport. SUMMARY: We discuss rehabilitation management when working with non-operative and operative management of patellar instability and provide considerations for clinicians working with these athletes to facilitate safe return to sport.

To quantify the severity of medial knee injuries based on medial compartment gapping as measured by stress ultrasonography.In 8 cadaveric knees, the distance between the medial tibial and femoral condyles was measured using ultrasonography. These measurements were obtained in the intact state and repeated after open sequential transection of the superficial medial collateral ligament (sMCL), deep medial collateral ligament (dMCL), posterior oblique ligament (POL), and arthroscopic transection of the anterior cruciate ligament (ACL). Knees were evaluated at 0° and 20° of knee flexion using the Telos device under 0 N and 100 N of valgus force. Receiver operating characteristic curve analysis and the DeLong test were used to determine whether measurements could distinguish between successive severity of MCL injury after identifying the optimal cutoff value for each injury state.Of the 8 cadaveric knees included in this study, 3 were male and 5 were female. The mean age was 58 ± 11 years (range 48-82 years). When measured using ultrasonography at 20° knee flexion with valgus load, the medial tibiofemoral distance significantly increased with increasing severity of medial knee injury (Dynamic ultrasonographic assessment can accurately quantify the severity of medial knee ligament injury based on medial compartment gapping. In our study, we found medial tibiofemoral distance13.8 mm at 20° knee flexion under valgus force indicates the presence of dMCL injury with a diagnostic accuracy of 0.97.Dynamic ultrasonography can quantify severity of medial knee injury without radiation and at point of care in multiple clinical settings.

To report the radiographic landmarks for the medial patellofemoral complex (MPFC) footprint on the medial femur and describe the difference between the radiographic positions corresponding to the medial quadriceps tendon femoral ligament (MQTFL) and medial patellofemoral ligament (MPFL) fibers.In 8 unpaired cadaveric knees, the MPFC footprint was exposed on the medial femur, and the proximal and distal boundaries of the footprint were marked. Lateral fluoroscopic images of the knee were obtained and analyzed using Image J. The proximal boundary corresponding to the MQTFL, the MPFC midpoint, and distal boundary corresponding to the MPFL were described radiographically and compared for differences in position.The proximal MQTFL footprint was 0.8 ± 0.6 mm anterior (P = .013) and 5.2 ± 1.8 mm proximal to the MPFC midpoint (P.001), whereas the distal MPFL footprint was 0.8 ± 0.7 mm posterior (P = .012) and 5.9 ± 1.1 mm distal to the radiographic MPFC midpoint (P.001). The radiographic point corresponding to the distal MPFL footprint was 0.8 ± 0.9 mm posterior (P = .011) and 11.1 ± 2.3 mm distal to the radiographic point of the proximal MQTFL footprint (P.001). When using the point of intersection of the posterior cortical line and the proximal posterior condyle as a reference, 91.6% of all points correlating to the MQTFL, MPFC midpoint and MPFL, were within 10 mm in any direction from this radiographic landmark.On fluoroscopic imaging, the proximal MQTFL and distal MPFL fibers had significantly different radiographic positions from the MPFC midpoint on the femur. These findings should be considered when reconstructing specific components of the MPFC.As fluoroscopy is often used intraoperatively to guide graft placement, our findings may serve as a reference when differentiating the locations of the MPFL vs MQTFL on the femur for anatomic reconstruction.

Congenital dislocation of the patella is a rare condition characterized by lateral dislocation of the patella that is irreducible without surgical correction. Although there is no clear inheritance pattern, it is associated with several congenital syndromes. Patients often demonstrate flexion contracture, loss of active knee extension, increased tibial external rotation, and absent patella in the trochlea. Treatment requires surgical management and is comprised of lateral release, medial stabilization, quadriceps lengthening, and distal realignment. Results are generally favorable after treatment; persistent flexion contracture and redislocation are the most common complications. Further study is needed to define the optimal timing and treatment strategy for this uncommon condition.

Most orthopaedic surgeons are unprepared for serious medical illnesses. In such cases, the unique work-related and personal considerations for orthopaedic surgeons affect their career, their practice partners, and their patients. Planning together as an orthopaedic business organization for such issues can provide a framework to better navigate these difficult situations. Understanding the considerations and stressors from the individual's perspective can help provide the appropriate level of support while maintaining privacy. Throughout these considerations, open communication regarding expectations and concerns and expressions of empathy are the cornerstones of dealing with physician illness. Being a physician-patient adds complexity to an already difficult and stressful profession. Further dialogue regarding the physician-patient experience can help increase awareness of this issue and allow organizations to create a structure to best manage this almost inevitable occurrence.

Hamstring injuries (HSI) are common in a number of different sports and can confer a significant burden to both male and female athletes. Though research on HSIs in the female athlete population is lacking, current literature suggests male athletes are between two to four times more likely than female athletes to sustain an HSI. Despite this discrepancy, the role of intrinsic sex differences in HSI risk factors has not been previously explored. This review aims to summarize these sex-based differences in HSI risk factors and their influence on the lower rate of HSIs seen in female athletes as compared to male athletes. Women exhibit increased hamstring flexibility and decreased hamstring musculotendinous stiffness as compared to men; women are also shown to be more resistant to skeletal muscle fatigue. Sex differences in the hamstring to quadriceps ratio and certain lower limb morphologies may also contribute to the sex discrepancy in HSI rates. This remains an area for future research in order to understand the multifaceted nature of HSI injury risk factors and optimize HSI rehabilitation and prevention programs for both male and female athletes.

The medial patellofemoral ligament (MPFL) has been known as the primary soft-tissue restraint to lateral patellar translation. More recent anatomic studies have identified additional fibers that extend to the quadriceps tendon (medial quadriceps tendon-femoral ligament [MQTFL]), leading to the use of the term "medial patellofemoral complex" (MPFC) to describe the broad and variable attachment of this complex on the patella and quadriceps tendon. Whereas many techniques and outcomes of traditional MPFL reconstruction have been described, fewer reports exist on anatomic MPFC reconstruction to recreate both bundles of this complex. To date, the specific biomechanical roles of, and indications for, reconstruction of the MPFL versus MQTFL fibers have not been defined. One primary benefit of MQTFL reconstruction has been to avoid the risk of patella fracture, which is not obviated in the setting of concurrent patellar fixation when reconstructing both components of the MPFC. The risks and benefits comparing fixation on the patella, quadriceps tendon, or both with anatomic double-bundle reconstruction remain to be determined. Additional studies are needed to understand the differences between reconstructing the proximal and distal fibers of the MPFC with regard to graft length changes and femoral attachment sites, in order to optimally recreate the function of each graft bundle in the surgical treatment of patellar instability.

Purpose To report the shape and orientation of the medial patellofemoral complex (MPFC) footprint on the medial femur and describe the difference between the proximal (medial quadriceps tendon femoral ligament, MQTFL) and distal (medial patellofemoral ligament, MPFL) fibers. Methods In 20 cadaveric knees, the MPFC footprint on the medial femur was exposed. Images of the medial femur were analyzed using ImageJ software. The length and width of the MPFC footprint were described to the nearest 0.1 mm; the angle of its long axis was described relative to the axis of the femoral shaft (0.1°). The footprint’s most proximal and distal margins were described in relation to the adductor tubercle and medial epicondyle. The differences between each were compared using paired t tests. Results 17 knees from 10 cadavers were included in this study. The MPFC footprint had a length of 11.7 ± 1.8 mm and a width of 1.7 ± 0.4 mm. The long axis of the footprint was at an angle 14.6° ± 16.6° anterior to the axis of the femoral shaft. The most proximal (MQTFL) fibers originated 7.4 ± 3.8 mm anterior and 1.8 ± 4.7 mm distal to the adductor tubercle and 4.1 ± 2.9 mm posterior and 8.4 ± 5.6 mm proximal to the medial epicondyle. The most distal (MPFL) fibers originated 4.9 ± 4.2 mm anterior and 12.7 ± 4.3 mm distal to the adductor tubercle, as well as 7.1 ± 2.4 mm posterior and 0.5 ± 5.6 mm distal to the medial epicondyle. The distal margin of the femoral MPFC footprint was 10.9 ± 1.7 mm distal (p Conclusions The femoral footprint of the MPFC has a length almost 7 times greater than its width, with the distal margin being 10.9 mm distal and 2.6 mm posterior to the proximal margin. Clinical Relevance This differential anatomy within the femoral origin suggests that MPFL and MQTFL reconstruction may require separate positions of femoral fixation to recreate the anatomy of these fibers.

Background: Medial patellofemoral complex (MPFC) reconstruction plays an important role in the surgical treatment of patellar instability. Anatomic reconstruction is critical in re-creating the native function of the ligament, which includes minimizing length changes that occur in early flexion. Anatomic risk factors for patellar instability such as trochlear dysplasia, patella alta, and increased tibial tuberosity to trochlear groove (TT-TG) distance have been shown to influence the function of the MPFC graft in cadaveric studies, but the native length change patterns of the MPFC fibers in knees with anatomic risk factors have not been described. Purpose: To describe the in vivo length changes of the MPFC fibers in knees with anatomic risk factors for patellar instability and identify the optimal attachment sites for MPFC reconstruction. Study Design: Controlled laboratory study. Methods: Dynamic computed tomography imaging was performed on the asymptomatic knee in patients with contralateral patellar instability. Three-dimensional digital knee models were created to assess knees between 0° and 50° of flexion in 10° increments. MPFC fiber lengths were calculated at each flexion angle between known anatomic attachment points on the extensor mechanism (quadriceps tendon, MPFC midpoint [M], and patella) and femur (1, 2, and 3, representing the proximal to distal femoral footprint). Changes in MPFC fiber length were compared for each condition and assessed for their relationships to morphologic risk factors (trochlear depth, Caton Deschamps Index [CDI], and TT-TG distance). Results: In 22 knees, native MPFC fibers were found to be longer at 0° than at 20° to 50° of flexion. Length changes observed between 0° and 50° increased with the number of risk factors present. In the central fibers of the MPFC (M-2), 1.7% ± 3.1% length change was noted in knees with no anatomic risk factors, which increased to 5.6% ± 4.6%, 17.0% ± 6.4%, and 26.7% ± 6.8% in the setting of 1, 2, and 3 risk factors, respectively. Nonanatomic patella-based attachments were more likely to demonstrate unfavorable length change patterns, in which length was greater at 50° than 0°. In patellar attachments, an independent relationship was found between increasing length changes and TT-TG distance, while in quadriceps tendon attachments, a trend toward a negative relationship between length changes and CDI was noted. All configurations demonstrated a strong relationship between percentage change in length and number of morphologic risk factors present, with the greatest influence found in patella-based attachments. Conclusion: The MPFC fibers demonstrated increased length changes in knees when a greater number of morphological risk factors for patellar instability were present, which worsened in the setting of nonanatomic configurations. This suggests that the function of the intact MPFC in patients with anatomic risk factors may not reflect previously described findings in anatomically normal knees. Further studies are needed to understand the pathoanatomy related to these changes, as well as the implications for graft placement and assessment of length changes during MPFC reconstruction techniques. Clinical Relevance: MPFC length change patterns vary based on the number of morphologic risk factors for patellar instability present and should be considered during reconstructive procedures.

A tendon’s ordered extracellular matrix (ECM) is integral for transmitting force and highly prone to injury. How tendon cells, or tenocytes, embedded within this dense ECM mobilize and contribute to healing is unknown. Here, we identify a specialized Axin2+ population in mouse and human tendons that remains latent in homeostasis yet initiates the healing response and serves as a major source of tendon progenitors. Axin2+ tenocytes readily expand in vitro and express stem cell markers. In vivo, Axin2+-descendants are major functional contributors to repair: Axin2+ tenocytes proliferate, acquire injury responsive states, and re-adopt a tenocyte fate post-injury. Specific loss of Wnt secretion in Axin2+ cells alters their progenitor identity, disrupts their activation upon injury, and severely compromises any healing response. Our work highlights an unusual paradigm, wherein quiescent Axin2+ tenocytes self-regulate their identity and mobilization upon injury and provide the key initiating signal to organize a tendon-wide healing response.

Several structures serve as primary static restraints to lateral and medial patellar displacement. Current evidence has demonstrated that there is a complex of ligaments both proximal (with corresponding attachments in the femur (medial patellofemoral ligament (MPFL) and medial quadriceps tendon femoral ligament (MQTFL)) and distal (medial patellotibial ligament (MPTL) and the medial patellomeniscal ligament (MPML)) that restrain lateral patellar translation at different degrees of knee flexion. Similarly, descriptions of proximal lateral restraints (with corresponding attachments on the femur (lateral patellofemoral ligament (LPFL)) and distal lateral restraints (lateral patellotibial ligament (LPTL) and lateral patellomeniscal ligament (LPML)) that restrain medial patellar translation have been described. Anatomical knowledge of these structures is of utmost importance for the diagnosis and treatment of these injuries. The purpose of this chapter is to report on the anatomical and surgical implications of the patellar restraints.

Objectives: Few imaging modalities currently exist that allow for dynamic assessment of the patellofemoral joint. Dynamic evaluation of patellar instability is typically based on physical examination using the Glide test to assess and quantify lateral patellar translation. However, this method can be limited for inexperienced examiners, and precise quantification with this method remains difficult. Therefore, this study aimed to utilize ultrasound imaging to quantify patellar position and translation under dynamic loading conditions to compare knees with and without injury to the medial soft tissue restraints. Methods: 10 fresh frozen, unpaired cadaveric knee specimens underwent assessment of lateral patellar translation using a portable ultrasound device. The probe was positioned 1cm above the medial joint line, and measurements were performed based on the distance between the articular edge of the medial patellar facet and the most prominent edge of the medial trochlear facet. Using an electronic force gauge, two standardized loading conditions were created: (1) Unloaded (0N of force), and (2) loaded with 20N of laterally directed force on the patella to mimic the Glide test. Patellar translation in the lateral direction was assessed from 0-40 degrees of knee flexion at 10 degree increments using a hand held goniometer. Measurements were performed in intact knees and were repeated after arthroscopic transection of the medial soft tissue restraints (both medial patellofemoral ligament [MPFL] and medial quadriceps tendon-femoral ligament [MQTFL]). All measurements were performed using Image J. Paired t-test was used to compare the findings of the intact vs injured states. Sensitivity, specificity, accuracy, negative, and positive predictive value for the injury state were determined based on the values from the intact state +2 standard deviations (SD). P-value Results: Compared with the intact state, significant increases in lateralized patellar position and translation were observed when the MPFL and MQTFL were transected, at all flexion angles between 0 and 40 degrees ( p values ranging from .005 to Conclusions: Under dynamic ultrasonographic assessment, the integrity of the medial patellar restraints can be effectively evaluated based on measurements of patellar position and translation, with patellar position >17.5mm from the medial trochlea at 20 and 30 degrees knee flexion indicating the presence of injury. As dynamic ultrasound can be performed without radiation or invasive testing in multiple clinical settings, further studies are recommended to assess the utility of ultrasound based assessments in the evaluation and management of patellar instability.

The role of medial patellofemoral ligament (MPFL) repair versus reconstruction in the treatment of patellar instability continues to undergo debate. Repair of the ligament can be technically less demanding with fewer risks of morbidity, whereas reconstruction carries concerns of graft malpositioning or over-tensioning as well as the risk of patellar fracture. Studies directly comparing the 2 procedures in the setting of recurrent patellar instability have consisted of small series or low levels of evidence that inevitably include patients with concurrent morphologic risk factors such as tuberosity malalignment or patella alta, which are known factors that can influence the biomechanical behavior of the MPFL. Heterogeneity in patient-related risk factors and surgical techniques continues to pose limitations in allowing for direct comparisons between procedures. For the treatment of recurrent patellar instability in the setting of no (or concurrently addressed) morphologic abnormalities, MPFL reconstruction has become a common procedure and generally preferred approach. The superior outcomes associated with reconstruction over repair, however, should be qualified with the fact that attention to the critical details of the technique, including graft position and tension, is paramount to success when performing this procedure.

The role of lateral retinacular release for the treatment of patellofemoral pathology has evolved over the years. Although once popularized in the treatment of patellofemoral pain and instability, complications such as iatrogenic medial patellar instability and decreases in lateral patellar stability have limited the indications for performing isolated lateral release. However, there exists a need for more clearly defined parameters and understanding of when and how lateral release should be incorporated with other procedures during patellar stabilization and joint-preservation surgery. Advances in finite element analysis, as well as refining our surgical indications and techniques for concurrent lateral release, will allow us to optimize both joint pressures and stability during the surgical management of patellar instability.

Our objective was to describe a measurement to assess sagittal tibial tuberosity (TT)-trochlear groove (TG) distance and to compare this between asymptomatic (control) patients and patients with symptomatic patellar instability.We compared static CT images of 22 fully extended knees of patients with symptomatic patellar instability with images of 22 asymptomatic knees. TT-TG distance was measured to quantify lateralization of the TT, and anteroposterior TT-TG distance was used to quantify the sagittal distance between these two points. Lateral trochlear inclination, sulcus angle, and trochlear depth were measured. Groups were compared using paired t tests (alpha = 0.05). Correlations of anteroposterior TT-TG distance with lateral trochlear inclination, sulcus angle, and trochlear depth were assessed using linear and multivariate regression.Mean TT-TG distances were 19.9 ± 4.4 mm (symptomatic) and 16.8 ± 5.5 mm (control) (mean ± std deviation) (P = 0.002). Mean anteroposterior TT-TG distances were 8.3 ± 7.8 mm (symptomatic) and -0.5 ± 4.6 mm (control) (P 0.0001). The symptomatic group had greater measurements of trochlear dysplasia, with lower lateral trochlear inclination, greater sulcus angle, and lower trochlear depth (all P 0.0001). Anteroposterior TT-TG distance and trochlear depth were strongly negatively correlated (r = 0.62, RIn asymptomatic patients, the anteroposterior TT-TG distance was -0.5 mm, indicating that the TG and TT were nearly in the same coronal plane. In patients with symptomatic patellar instability, the TG was almost nine millimeters anterior, and this distance correlated with measurements of trochlear dysplasia.III, case control study.

From the Editor, Dr. Miho J. Tanaka Journal of Women's Sports Medicine

Purpose To arthroscopically describe patellar position based on lateralization, tilt, and engagement, and compare measurements in normal, medial patellofemoral complex-(MPFC) deficient, and MPFC-reconstructed knees. Methods In 10 cadaveric knees, arthroscopic patellar position was assessed by performing digital measurements on arthroscopic images obtained through a standard anterolateral portal. Lateralization was measured as millimeters overhang of the patella past the lateral edge of the lateral femoral condyle, viewing from the lateral gutter. Patellar tilt was calculated as the difference in medial and lateral distances from the patella to the trochlea, viewing from the sunrise view. Patellotrochlear distance was measured as the anteroposterior distance between the central trochlear groove and patella on the sunrise view. Measurements were obtained at 10° intervals of knee flexion from 0° to 90°, in intact knees (group 1), after arthroscopically transecting the MPFC fibers (group 2), and after MPFC reconstruction (group 3). Optimal cutoff values were identified to distinguish between intact versus MPFC-deficient states. Results When compared to group 1, group 2 demonstrated increased patellar lateralization by 22.5% at 0°-40° knee flexion (P = .006), which corrected to baseline in group 3 (P = .006). Patellar tilt measurements demonstrated no differences between groups. Patellotrochlear distance increased by 21.0% after MPFC transection (P = .031) at 0°-40° knee flexion, with correction to baseline after MPFC reconstruction (P = .031). More than 7 mm of lateral overhang at 20°-30° flexion and >6 mm of patellotrochlear distance at 10°-20° flexion were found to indicate MPFC deficiency. Conclusions Utilizing standardized arthroscopic views, we identified significant increases in patellar lateralization and patellotrochlear distance in early knee flexion angles after MPFC transection, and these changes normalized after MPFC reconstruction. Clinical Relevance Arthroscopic assessments of patellar position may be useful in evaluating patellofemoral stability during patellar stabilization surgery.

Knee pain can be a common complaint during pregnancy; however, the severity of symptoms and their associated risk factors have not been described.The aim of this study was to characterize knee-related dysfunction and describe risk factors in a general obstetric population.Patients in obstetric clinics completed the International Knee Documentation Committee (IKDC) questionnaire to assess their knee function, as well as the Pregnancy Physical Activity Questionnaire (PPAQ), a validated tool to assess physical activity. Age, weeks gestation, height, weight, and history of knee problems prior to pregnancy were analyzed to identify independent associations with IKDC score and determine predictors of knee dysfunction.310 patients were included in this study, of which 68, 111 and 131 were in their first, second and trimesters, respectively. Mean age of the total study group was 30.3 ± 5.5 years. Knee function decreased with each trimester, from a mean IKDC score of 88.9 ± 13.0 in the first trimester, 84.5 ± 16.8 in the second, and 82.0 ± 20.0 in the third, with corresponding decreases in activity levels of 258.5 ± 141.7, 254.0 ± 141.5, and 246.1 ± 156.6 MET-h/wk. Of the total study group, 26.1% had IKDC scores75, including 13.2%, 25.2%, and 33.6% in the first, second and third trimesters. Risk factors for knee dysfunction included high activity levels of PPAQ ≥ 500 MET-h/wk (OR 2.8), history of knee problems (OR 2.7), age 25 years (OR 2.6), and BMI ≥ 30 kg/mIn our cohort, 26.1% of pregnant women reported severe knee dysfunction, and this was associated with high levels of activity, younger age, greater BMI, and history of knee problems. These findings may have implications for women who wish to maintain training and fitness during pregnancy. Future studies are recommended to assess the need for intervention, as well as to identify optimal methods to prevent and address symptoms in this population.IV, Case Series.

Trochlear dysplasia is one of the primary morphologic abnormalities associated with patellar instability. Although qualitative classifications based on trochlear shape such as the Dejour classification exist, radiographic measurements to quantify the severity of trochlear dysplasia are numerous and varied. Each measurement addresses a different element of the complex and wide-ranging presentations that exist along a spectrum of abnormalities in trochlear morphology, and the reported reliability of such measurements are mixed. Overall, our understanding of trochlear dysplasia continues to evolve, and the ability to quantify the morphology of the trochlea, as well as its influence on patellar stability, remains a work in progress. Future directions include developing improved 3-dimensional descriptions of trochlear anatomy, as well as standardizing measurement methods and image slice selection, to better evaluate trochlear morphology in the assessment of patellar instability.

The number of female athletes has grown exponentially since Title IX. However, little data exists on the proportion of women and girls who play each sport.To quantify changes in female sports participation in high school sports from 1973 to 2018.Retrospective analysis of data from the National Federation of State High School Associations Participation Survey.US high schools.US high school athletes from 1973 to 2018.Percentage of female participation for each high school sport in 5-year intervals; and changes in rates of participation by player gender and sport at designated intervals.From 1973 to 2018, the percentage of high school sports played by girls increased from 24.2% to 42.9% ([95%CI, 18.6,18.8], p 0.0001). In the 14 sports included in our study, all had an increase in the percentage of female participation between 1973 and 2018.80% of the increases occurred between 1973 and 1998 for all sports except lacrosse, ice hockey, football, and wrestling. Between 1998 and 2018, the percentage of girls playing each sport increased by less than 5% in all sports, except for ice hockey (11.5%, 95% CI 11.0, 12.0, p 0.001) and wrestling (7.1%, 95% CI 6.9, 7.1, p 0.001).Girls' participation in high school sports continues to grow not only in numbers but in the types of sports played. Between 1998 and 2018, the greatest increases were noted in ice hockey and wrestling, which had fewer than 1% female participation before 1998. Physicians providing care for female athletes should be aware of these changes and understand the potential injuries associated with these sports.

Background Patella alta reduces articular constraints acting on the patella from the trochlear groove with the knee extended. The current study was performed to address how patella alta alters the influence of tibial tuberosity position and trochlear depth on patellar tracking in patients being treated for patellar instability. Methods Fifteen subjects with recurrent patellar instability participated in knee extension within a dynamic CT scanner. Computational models were reconstructed from the motions to characterize patellar lateral shift, patellar tilt, patellar height, trochlear depth and lateral position of the tibial tuberosity at 0° and 30° of knee flexion. Linear regressions were used to correlate patellar tracking with anatomy for an alta group (7 knees, Caton-Deschamps index > 1.2) and a non-alta group. Findings For the alta group, lateral patellar shift and tilt increased with increasing lateral position of the tibial tuberosity at 0° (r2 > 0.8, P 0.8, P = 0.001). Lateral patellar tilt also increased with increasing lateral position of the tibial tuberosity at 30° for the non-alta group (r2 = 0.55, P = 0.04). Interpretation For patients with patellar instability, lateral patellar maltracking with the knee extended can be largely attributed to either a shallow trochlear groove or a combination of patella alta and a lateral position of the tibial tuberosity. These relationships should be considered in both conservative and surgical treatment planning.

Optimal treatment of patients with patellofemoral trochlear dysplasia and recurrent patellar instability requires in-depth understanding of this complex structural anomaly. An extensive review of the literature suggests that dysplasia occurs as a result of aberrant forces applied to the patellofemoral joint in the majority of cases. Evidence supports surgical stabilization that reconstructs the medial patellofemoral and/or medial quadriceps tendon–femoral ligament without added trochleoplasty in the majority of patients with trochlear dysplasia and recurrent patellar instability. Adding tibial tubercle transfer distally, medially, or anteromedially in those who need it to treat specific deficits in alignment or articular cartilage can be beneficial in selected patients with trochlear dysplasia and recurrent patellar instability. Trochleoplasty may be appropriate in those few cases in which permanent stable patellofemoral tracking cannot be restored otherwise, but the indications are not yet clear, particularly as trochleoplasty adds risk to the articular cartilage. Improved understanding of imaging techniques and 3-dimensional reproductions of dysplastic patellofemoral joints are useful in surgical planning for patients with recurrent patellar instability and trochlear dysplasia.

Objectives: Patella alta is a risk factor for patellar instability and its recurrence after treatment. The patellotrochlear index (PTI) is a measurement used to quantify patella alta, describing patellar engagement in the trochlea through an index of trochlear overlap with patellar articular surface based on sagittal imaging. Values less than 20% have been reported to indicate patella alta, yet this measurement has primarily been described in normal knees. Trochlear dysplasia is also a common risk factor in patellar instability and can affect the length of the trochlea. Therefore the purpose of this study was to compare PTI measurements in knees with and without trochlear dysplasia, and to describe its relationship with trochlear length. Methods: Knees with trochlear dysplasia (defined by trochlear depthResults: 21 knees with trochlear dysplasia (13 female and 8 male) were included in this study, and were compared with 21 age- and gender-matched controls. In the dysplastic group, trochlear depth (TD) was 0.7+/-2.4mm vs 6.8+/-2.5mm (pConclusion: In this study, knees with trochlear dysplasia had a PTI of 35% vs 25% in the control group, indicating greater patellar engagement despite having greater measurements of patella alta based on CDI (1.19 vs 1.06). PTI correlated with increased proximal extension of the trochlea which may account for the greater patellofemoral overlap. As abnormal trochlear length can associated with supratrochlear spurs, greater values on PTI may not necessarily indicate functional patellofemoral engagement. Further studies are needed to identify the functional relationship between trochlear length and patella alta.

Objectives: The medial patellofemoral complex (MPFC) includes the medial patellofemoral ligament (MPFL) and medial quadriceps tendon femoral ligament (MQTFL). Recent reports have described reconstruction of this fan-shaped ligament to treat patellar instability using a double stranded technique to recreate both components of the complex, with a common origin on the medial femur. Much effort has been placed on accurately identifying the “point” of femoral origin during reconstruction due to the influence of femoral tunnel position on MPFC graft function, however, the MPFC origin is elongated in nature. Therefore, the purpose of this study was to describe the shape and orientation of the MPFC origin and identify the difference between the most proximal and distal margins of the elongated femoral footprint. Methods: 20 paired fresh frozen cadaveric knees were dissected. From an intraarticular approach, the MPFC was exposed and followed to its footprint on the medial femur. All other soft tissue was removed from the distal femur, and the footprint of the MPFC, the adductor tubercle and medial epicondyle were marked. Images of the medial femur were analyzed using Image J software. The length and width of the MPFC footprint was described to the nearest 0.1mm, as well as the angle of the long axis of the footprint relative to the axis of the femoral shaft (0.1 degrees). The position of the footprint’s most proximal and distal margins were identified and described in relation to the adductor tubercle and medial epicondyle. The positions for each were compared using paired t tests. Results: 17 knees from 10 cadavers (7M, 3F, mean age 73.1) were included in this study. The MPFC femoral footprint had a length of 11.7mm+/-1.8mm (Range 9.6,15.7) and a width of 1.7mm+/-0.4mm (Range, 0.9, 2.2). The long axis of the footprint was found to lie at an angle 14.6+/-16.6 degrees anterior to the axis of the femoral shaft. The most proximal fibers originated 7.4mm+/-3.8mm anterior and 1.8mm+/-4.7mm distal to the adductor tubercle, and 4.1mm+/-2.6mm posterior and 8.4mm+/-5.6mm proximal to the medial epicondyle. The most distal fibers originated 4.9mm+/-4.2mm anterior and 1.3mm+/-4.3mm and distal to the adductor tubercle, as well as 7.1mm+/-2.4mm posterior and 0.5mm+/-5.6mm distal to the medial epicondyle. Overall, the distal margin of the footprint was 10.9mm+/-1.7mm distal (pConclusions: The femoral footprint of the MPFC is ribbon shaped, with the distal margin being 10.9 mm distal and 2.6 mm posterior to the proximal margin. This differential anatomy of the femoral origin suggest that MPFL and MQTFL reconstruction may require separate placements of the femoral tunnels to anatomically recreate these fibers. Further biomechanical studies are needed to determine the optimal femoral tunnel placement in the setting of double-limbed MPFC reconstruction, as well as the long term benefit of this technique in the treatment of patellar instability.

Orthopaedic practices have been markedly affected by the emergence of the COVID-19 pandemic. Despite the ban on elective procedures, it is impossible to define the medical urgency of a case solely on whether a case is on an elective surgery schedule. Orthopaedic surgical procedures should consider COVID-19-associated risks and an assimilation of all available disease dependent, disease independent, and logistical information that is tailored to each patient, institution, and region. Using an evidence-based risk stratification of clinical urgency, we provide a framework for prioritization of orthopaedic sport medicine procedures that encompasses such factors. This can be used to facilitate the risk-benefit assessment of the timing and setting of a procedure during the COVID-19 pandemic.

With the onset of the COVID-19 pandemic, the shifting of clinical care to telemedicine visits has been hastened. Because of current limitations in resources, many elective surgeons have been forced to venture into utilizing telemedicine, in which the standards for orthopaedic examinations have not previously been fully developed. We report our experience with protocols and methods to standardize these visits to maximize the benefit and efficiency of the virtual orthopaedic examination. At the time of scheduling, patients are asked to prepare for their virtual visit and are given a checklist. In addition to confirming audiovisual capabilities prior to the visit, patients are given specific instructions on camera positioning, body positioning, setting, and attire to improve the efficiency of the visit. During the examination, digital tools can be utilized as needed. In the setting of outpatient injury evaluations, a systematic virtual examination can aid in triaging and managing common musculoskeletal conditions. With the rapid incorporation of telehealth visits, as well as the unknown future with regard to the pandemic, the utilization and capabilities of telemedicine will continue to expand. Future directions include the development of validated, modified examination techniques and new technology that will allow for improved interactive physical examinations, as we rapidly move forward into the realm of telemedicine due to unexpected necessity.

ContextNeuromuscular training programs can reduce the rate of noncontact anterior cruciate ligament (ACL) injuries, particularly in female athletes.ObjectiveTo assess the awareness of, experience with, and factors associated with participation in preventive training programs (PTPs) among female collegiate athletes and their knowledge of ACL injuries.DesignCross-sectional study.SettingNational Collegiate Athletic Association (NCAA) sports programs.Patients or Other ParticipantsA total of 440 female NCAA athletes (age = 20 ± 1 years) representing 20 sports during the 2017–2018 academic year.Main Outcome Measure(s)We used a 12-item survey to collect data on each participant's age, sport, position, college, NCAA division, and awareness of and experience with PTPs. We performed descriptive statistics and used odds ratios (ORs) to assess relationships between demographic data and awareness of or interest in PTPs.ResultsOf the 440 respondents, 85% (n = 373) knew that female athletes were at higher risk for sustaining ACL injuries than male athletes, and 89% (n = 391) knew that ACL injuries were preventable. Thirty-three percent (n = 143) were familiar with the concept of ACL PTPs. Only 15% (n = 64) had ever performed PTPs, but 89% (n = 391) reported they would perform a daily PTP if it could prevent ACL injuries. Fifty-two of the 64 respondents (81%) who had performed PTPs said athletic trainers or coaches oversaw the PTPs. Participants were more likely to be familiar with ACL PTPs if they (OR = 3.5; 95% confidence interval [CI] = 2.0, 5.8) or a teammate (OR = 4.6; 95% CI = 2.1, 9.8) had sustained an ACL injury. Respondents were more willing to perform PTPs if they (OR = 2.3; 95% CI = 0.80, 6.6) or a teammate (OR = 3.4; 95% CI = 1.8, 6.6) had sustained an ACL injury.ConclusionsAlthough 89% of respondents expressed interest in performing daily ACL PTPs, only 15% had performed such programs, and only 33% were familiar with the concept of ACL PTPs.

Medial patellofemoral ligament (MPFL) reconstruction is currently the primary surgical procedure for treating recurrent lateral patellar instability. The understanding of graft function has largely been based on studies performed with normal knees. The current study was performed to characterize graft function following MPFL reconstruction, focusing on the influence of pathologic anatomy on graft tension, variations with knee flexion, and the influence on patellar tracking. Knee squatting was simulated with 15 multibody dynamic simulation models representing knees being treated for recurrent lateral patellar instability. Squatting was simulated in a preoperative condition and following MPFL reconstruction with a hamstrings tendon graft set to allow 0.5 quadrants of lateral patellar translation with the knee at 30 degrees of flexion. Linear regressions were performed to relate maximum tension in the graft to parameters of knee anatomy. Repeated measures comparisons evaluated variations in patellar tracking at 5-degree increments of knee flexion. Maximum graft tension was significantly correlated with a parameter characterizing lateral position of the tibial tuberosity (maximum lateral tibial tuberosity to posterior cruciate ligament attachment distance, r 2 = 0.73, p

Background: The use of imaging to diagnose patellofemoral instability is often limited by the inability to dynamically load the joint during assessment. Therefore, the diagnosis is typically based on physical examination using the glide test to assess and quantify lateral patellar translation. However, precise quantification with this technique remains difficult. Purpose: To quantify patellar position using ultrasound imaging under dynamic loading conditions to distinguish between knees with and without medial patellofemoral complex (MPFC) injury. Study Design: Controlled laboratory study. Methods: In 10 cadaveric knees, the medial patellofemoral distance was measured to quantify patellar position from 0° to 40° of knee flexion at 10° increments. Knees were evaluated at each flexion angle under unloaded conditions and with 20 N of laterally directed force on the patella to mimic the glide test. Patellar position measurements were made on ultrasound images obtained before and after MPFC transection and compared for significant differences. To determine the ability of medial patellofemoral measurements to differentiate between MPFC-intact and MPFC-deficient states, area under the receiver operating characteristic (ROC) curve analysis and the Delong test were used. The optimal cutoff value to distinguish between the deficient and intact states was determined using the Youden J statistic. Results: A significant increase in medial patellofemoral distance was observed in the MPFC-deficient state as compared with the intact state at all flexion angles ( P = .005 to P < .001). When compared with the intact state, MPFC deficiency increased medial patellofemoral distance by 32.8% (6 mm) at 20° of knee flexion under 20-N load. Based on ROC analysis and the J statistic, the optimal threshold for identifying MPFC injury was 19.2 mm of medial patellofemoral distance at 20° of flexion under dynamic loading conditions (area under the ROC curve = 0.93, sensitivity = 77.8%, specificity = 100%, accuracy = 88.9%). Conclusion: Using dynamic ultrasound assessment, we found that medial patellofemoral distance significantly increases with disruption of the MPFC. Clinical Relevance: Dynamic ultrasound measurements can be used to accurately detect the presence of complete MPFC injury.

The scientific literature concerning the anatomy of medial soft-tissue stabilizers of the patella is growing exponentially. Much of the surgical literature has focused on the role of the medial patellofemoral ligament (MPFL) and techniques to reconstruct it, yet our understanding of its anatomy has evolved during the past several years. Given this, we report on the current understanding of medial patellofemoral anatomy and implications for reconstruction. Current and historical studies of medial patellar anatomy were reviewed, which include the MPFL and medial quadriceps tendon femoral ligament (MQTFL), as well as that of the distal medial patellar restraints, the medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML). In addition to the reported findings, the authors’ anatomic descriptions of each ligament during their dissections were identified and recorded. Despite the name of the MPFL, which implies that the ligament courses between the femur and patella, recent studies have highlighted the proximal MPFL fibers that attach to the quadriceps tendon, known as the MQTFL. The MPFL and MQTFL have also been referred to as the medial patellofemoral complex, reflecting the variability in anatomical attachment sites. The MPFL accounts for only half of the total restraint to lateral patellar displacement, and the remaining contributions to patellar stability are derived from the combination of the MPTL and MPML, which function primarily in greater degrees of knee flexion. The understanding of the complexity of the medial patellar stabilizers continues to evolve. Although MPFL reconstruction is gaining wide acceptance as a procedure to treat patellar instability, it is important to recognize the complex and changing understanding of the anatomy of the medial soft-tissue stabilizers and the implications for reconstruction. V.

Background Medial patellofemoral ligament reconstruction and tibial tuberosity anteromedialization are common treatment options for recurrent lateral patellar instability, although ligament reconstruction is not commonly applied to knees with lateral malalignment. Methods Multibody dynamic simulation was used to assess knee function following tibial tuberosity anteromedialization and medial patellofemoral ligament reconstruction for knees with lateral malalignment. Dual limb squatting was simulated with six models representing knees being treated for patellar instability with an elevated tibial tuberosity to trochlear groove distance. The patellar tendon attachment on the tibia was shifted medially (10 mm) and anteriorly (5 mm) to represent tibial tuberosity anteromedialization. A hamstrings tendon graft was represented for medial patellofemoral ligament reconstruction. Patellar tracking was quantified based on bisect offset index. The patellofemoral contact pressure distribution was quantified using discrete element analysis. Data were analyzed with repeated measures comparisons with post-hoc tests. Findings Both procedures significantly reduced bisect offset index, primarily at low flexion angles. The decrease was larger for tibial tuberosity anteromedialization, peaking at 0.18. Tibial tuberosity anteromedialization shifted contact pressures medially, significantly increasing the maximum medial contact pressure at multiple flexion angles, with the maximum pressure increasing up to 1 MPa. Interpretation The results indicate tibial tuberosity anteromedialization decreases lateral patellar maltracking more effectively than medial patellofemoral ligament reconstruction, but shifts contact pressure medially. Tibial tuberosity anteromedialization is likely to reduce the risk of post-operative instability compared to medial patellofemoral ligament reconstruction. The medial shift in the pressure distribution should be considered for knees with medial cartilage lesions, however.

Background:Abnormal patellar tracking is described as a “J-sign” when the patella exhibits excessive lateral displacement during active knee extension.Purpose:To determine (1) the accuracy and reliability of the visual assessment of patellar tracking when viewed by surgeons with patellofemoral expertise and (2) whether surgeon experience (in years) correlates with the ability to accurately identify the presence and severity of patellar maltracking.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:Using a web-based assessment, 32 orthopaedic surgeon members of the International Patellofemoral Study Group determined the presence or absence of maltracking (≥2 quadrants of lateral translation) in 10 single-knee videos of patients with patellar instability during active knee extension (qualitative analysis). Surgeons then graded patellar tracking in 20 single-knee videos as follows: 0 (Results:In the qualitative analysis, surgeons correctly identified videos as showing patellar maltracking 68% of the time (κ = 0.45). In the quantitative analysis, 53%, 51%, 48%, and 68% of surgeons correctly identified maltracking of grades 3, 2, 1, and 0, respectively (κ = 0.42). Surgeon experience did not correlate with ability to identify the presence ( P = .59) or grade ( P = .35) of patellar maltracking. Respondent answers from the second survey demonstrated inadequate intraobserver reliability (κ = 0.48).Conclusion:Using visual assessment alone, surgeons correctly identified patellar maltracking in approximately two-thirds of videos and correctly graded patellar maltracking in half. Inter- and intraobserver reliability were inadequate to support the use of visual assessment alone for detecting the presence or grade of patellar maltracking. Surgeon experience did not correlate with ability to identify the presence or grade of patellar maltracking.