Patellofemoral Instability

Recurrent patellofemoral instability is a common cause of knee pain and functional disability in adolescent and young adult patients, resulting in loss of time from work and sports. There are numerous factors that contribute to recurrent patellofemoral instability; these factors include tear of the medial patellofemoral ligament (MPFL), weakening or hypoplasia of the vastus medialis obliquus (VMO), trochlear dysplasia, increased tibial tuberosity-trochlear groove (TT-TG) distance (>20 mm), valgus malalignment, increased Q angle, malrotation secondary to internal femoral or external tibial torsion, patella alta, and generalized ligamentous laxity. A detailed history and a thorough physical examination are crucial to clinch an early, accurate diagnosis. Imaging studies play an important role to confirm the clinical diagnosis and also help to identify concomitant intra-articular pathologies. Initially, nonoperative management (including the use of physical therapy, patellar taping or brace) is offered to patients with acute, first-time patellar dislocations and most patients respond well to this mode of treatment. Surgical treatment is indicated for patients who have post-trauma osteochondral fracture or loose body; predisposing anatomical risk factors; recurrent, symptomatic instability; and who have failed an adequate trial of nonoperative management. Surgical treatments include MPFL reconstruction, proximal or distal realignment procedures, and trochleoplasty. Lateral release is often performed in combination with other procedures and seldom performed as an isolated procedure. An individualized case-by-case approach is recommended based on the underlying anatomical risk factors and radiographic abnormality.

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Isolated Medial Patellofemoral Ligament Reconstruction Can Be an Effective Procedure in Patellofemoral Instability with Risk Factors

The Journal of Knee Surgery ◽

10.1055/s-0039-1688917 ◽

2019 ◽

Vol 33 (10) ◽

pp. 992-997 ◽

Cited By ~ 4

Author(s):

Fabian Blanke ◽

Kathrin Watermann ◽

Maximilian Haenle ◽

Andreas Feitenhansl ◽

Carlo Camathias ◽

...

Keyword(s):

Risk Factors ◽

Clinical Outcome ◽

Medial Patellofemoral Ligament ◽

Trochlear Dysplasia ◽

Patellofemoral Instability ◽

Effective Procedure ◽

Mpfl Reconstruction ◽

Trochlear Groove ◽

Severe Problem ◽

Outcome Scores

AbstractPatellofemoral instability is a severe problem in young and active patients. This pathology is influenced by ligamentous, bony, and neuromuscular parameters. The reconstruction of the medial patellofemoral ligament (MPFL) evolved to a primary procedure, but combined procedures were more frequently performed in the past years. However, additional operative procedures are associated with increased morbidity and no absolute indication can be identified in the literature. This study is intended to clarify whether addressing only ligamentous influence factors (MPFL) in chronic patellofemoral instability is sufficient to produce good clinical outcomes, or whether other risk factors influence the results negatively and should also be treated at some point. In 52 patients with chronic patellofemoral instability patellar height according to Caton-Deschamps, trochlear dysplasia according to Dejour, the leg axis, the femoral antetorsion, tibial tubercle (TT)–trochlear groove, and TT–posterior cruciate ligament distance were evaluated. All patients were treated with isolated MPFL reconstruction. After a minimum follow-up period of 24 months (24–36 months), the clinical outcome results were calculated using the scoring system according to Lysholm and Tegner. Correlation between clinical outcome scores and anatomic risk factors were calculated. The analysis was performed using a standard statistical software package (JMP version 12, SAS Institute, Cary, NC). The average postoperative Lysholm score increased significantly from 57.23 ± 19.9 to 85.9 ± 17.2 points (p < 0.0001) after isolated MPFL reconstruction. Moreover, the Tegner and Lysholm scores significantly improved both in patients without and with different risk factors postoperative. There were no significant differences in the outcome sores between the groups. Even the degree of trochlear dysplasia (types I–III) did not influence the results. Finally, there was no significant correlation found between all collected risk factors and the postoperative outcome scores. Isolated MPFL reconstruction can be an effective procedure in patients with patellofemoral instability and mild to moderate risk factors.

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Anatomic Risk Factors for Focal Cartilage Lesions in the Patella and Trochlea: A Case-Control Study

The American Journal of Sports Medicine ◽

10.1177/0363546519859320 ◽

2019 ◽

Vol 47 (10) ◽

pp. 2444-2453 ◽

Cited By ~ 10

Author(s):

Luiz Felipe Ambra ◽

Betina B. Hinckel ◽

Elizabeth A. Arendt ◽

Jack Farr ◽

Andreas H. Gomoll

Keyword(s):

Risk Factors ◽

Trochlear Dysplasia ◽

Cartilage Lesion ◽

Patella Alta ◽

Lesion Group ◽

Control Group ◽

Trochlear Groove ◽

Patellar Tilt ◽

Sulcus Angle ◽

Cartilage Lesions

Background:Focal cartilage lesions in the patellofemoral (PF) joint are common. Several studies correlated PF risk factors with PF instability, anterior knee pain, and PF arthritis; however, there is a lack of evidence correlating those factors to PF focal cartilage lesions.Purpose:To evaluate the influence of the anatomic PF risk factors in patients with isolated focal PF cartilage lesions.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Patients with isolated PF focal cartilage lesions were included in the cartilage lesion group, and patients with other pathologies and normal PF cartilage were included in the control group. Multiple PF risk factors were accessed on magnetic resonance imaging scans: patellar morphology (patellar width, patellar thickness, and patellar angle), trochlear morphology (trochlear sulcus angle, lateral condyle index, and trochlear sulcus depth), patellar height (Insall-Salvati ratio and Caton-Deschamps index), axial patellar positioning (patellar tilt, angle of Fulkerson), and quadriceps vector (tibial tuberosity–trochlear groove distance).Results:A total of 135 patients were included in the cartilage lesion group and 100 in the control group. As compared with the control group, the cartilage lesion group had a higher sulcus angle ( P = .0007), lower trochlear sulcus depth ( P < .0001), lower angle of Fulkerson ( P < .0001), lower patellar width ( P = .0003), and higher Insall-Salvati ratio ( P < .0001). From the patients in the cartilage lesion group, 36% had trochlear dysplasia; 27.6%, patella alta; and 24.7%, abnormal patellar tilt. These parameters were more frequent in the cartilage lesion group ( P < .0001). Trochlear lesions were more frequent in men, presented at an older age, and had fewer associated anatomic risk factors. Patellar lesions, conversely, were more frequent in women, presented at younger age, and were more closely associated with anatomic risk factors.Conclusion:PF anatomic abnormalities are significantly more common in patients with full-thickness PF cartilage lesions. Trochlear dysplasia, patella alta, and excessive lateral patellar tilt are the most common correlated factors, especially in patellar lesions.

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No growth disturbance after trochleoplasty for recurrent patellar dislocation in adolescents with open growth plates

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967119s00221 ◽

2019 ◽

Vol 7 (6_suppl4) ◽

pp. 2325967119S0022

Author(s):

Sean Robert Williams ◽

Manfred Nelitz

Keyword(s):

Trochlear Dysplasia ◽

Patellofemoral Instability ◽

Trochlear Groove ◽

Growth Disturbance ◽

Growth Plates ◽

Leg Axis ◽

Kujala Score ◽

Open Growth Plates ◽

Open Growth

Aims and Objectives: Trochlear dysplasia is the most important risk factor to patellofemoral instability in adolescents, therefore trochleoplasty to reshape the trochlear groove is the treatment of choice in patients with severe trochlear dysplasia. However, in the presence of open growth plates there is a potential risk of injury of the distal femoral growth plate and subsequent growth disturbance. Therefore, most authors do not recommend trochleoplasty in skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear. The hypothesis of the study was, that In patients with open growth plates and an expected growth of less than two years trochleoplasty does not cause growth disturbance of the distal femur. Materials and Methods: 18 consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent trochleoplasty. Pre- and postoperative radiographic examination included AP and lateral views to assess leg axis and patella alta. Preoperatively a radiograph of the left hand was performed to measure skeletal age. MRI was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TT-TG) distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, Activity Rating Scale (ARS) and Tegner activity score. Results: The average age at the time of operation was 12.6 y (range, 12.2 - 13.3) in girls and 14.5 y (14.0 - 15.4) in boys. The average follow-up after operation was 2.3 years after surgery (range, 2.0 - 3.0 years). At follow-up in all patients the growth plates of the knee were closed. Impairment of growth of the distal femur was neither found clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score and median VAS showed significant improvement (p < 0.01). The activity level according to the Tegner activity score did not change statistically significant. Conclusion: In this study, trochleoplasty as a treatment for patellofemoral instability in patients with open physes and an expected growth of not more than two years showed good clinical results without redislocation and no growth disturbance. Therefore, in selected adolescent patients with severe trochlear dysplasia trochleoplasty can be safely performed up to two years before the projected end of growth.

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No Growth Disturbance After Trochleoplasty for Recurrent Patellar Dislocation in Adolescents With Open Growth Plates

The American Journal of Sports Medicine ◽

10.1177/0363546518794671 ◽

2018 ◽

Vol 46 (13) ◽

pp. 3209-3216 ◽

Cited By ~ 14

Author(s):

Manfred Nelitz ◽

Jens Dreyhaupt ◽

Sean Robert March Williams

Keyword(s):

Trochlear Dysplasia ◽

Patellofemoral Instability ◽

Trochlear Groove ◽

Growth Disturbance ◽

Growth Plates ◽

Leg Axis ◽

Kujala Score ◽

Open Growth Plates ◽

Open Growth

Background: Trochlear dysplasia is the most important risk factor for patellofemoral instability among adolescents; therefore, trochleoplasty to reshape the trochlear groove is the treatment of choice for patients with high-grade trochlear dysplasia. However, in the presence of open growth plates, there is a potential risk of injury to the distal femoral growth plate and subsequent growth disturbance. As such, most authors do not recommend trochleoplasty for skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear. Hypothesis: For patients with open growth plates and an expected growth <2 years, trochleoplasty does not cause growth disturbance of the distal femur. Study Design: Case series; Level of evidence, 4. Methods: Eighteen consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent thin flap trochleoplasty. Pre- and postoperative radiographic examination included anteroposterior and lateral views to assess leg axis and patella alta. A preoperative radiograph of the left hand was performed to measure skeletal age. Magnetic resonance imaging was performed to evaluate trochlear dysplasia and tibial tubercle–trochlear groove distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, and Tegner activity score. Results: The median age at the time of operation was 12.6 years (range, 12.2-13.3 years) for girls and 14.5 years (14.0-15.4 years) for boys. The mean follow-up after operation was 2.3 years after surgery (range, 2.0-3.0 years). At follow-up for all patients, the growth plates of the knee were closed. Impairment of growth of the distal femur was found neither clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score improved significantly from 67 (range, 54-75) preoperatively to 89.5 (range, 78-96) at follow-up ( P < .01). The median visual analog scale showed significant pre- to postoperative improvement from 5 (range, 3-7) to 1 (range, 0-3) ( P < .01). The activity level according to the Tegner activity score did not change significantly. Conclusion: In this study, trochleoplasty as a treatment for patellofemoral instability of patients with open physes and an expected growth of not more than 2 years showed good clinical results without redislocation and with no growth disturbance. Therefore, for selected adolescent patients with high-grade trochlear dysplasia, trochleoplasty can be safely performed up to 2 years before the projected end of growth.

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What sports medicine practitioners should know about imaging for femoro-patellar pathologies

Swiss Sports & Exercise Medicine ◽

10.34045/ssem/2020/1 ◽

2020 ◽

Vol 68 (1) ◽

Keyword(s):

Risk Factors ◽

Knee Pain ◽

Anterior Knee Pain ◽

High Reliability ◽

Trochlear Dysplasia ◽

Trochlear Groove ◽

Clinical Imaging ◽

Adequate Treatment ◽

Patellar Maltracking ◽

Anterior Knee

Clinical imaging in patellofemoral disorders is fundamental for the understanding of the pathology, and to find the adequate treatment option. Anatomical risk factors such as trochlear dysplasia, patella alta, lateralized tibiale tubercle (measured by the tibiale tubercle trochlear groove distance), torsional or coronal lower limb alignment that are the origine of patellar maltracking or even patellar dislocation, can be assessed with high reliability on conventional radiographs combined with MR imaging. The conservative and surgical treatment will highly rely on these findings. The importance of clinical imaging in unspecific anterior knee pain is less clear. It is mostly performed to exclude structural injuries, however is rarely reliable to diagnose the painful structure. Critical appraisal of morphological risk factors is necessary especially in the treatment of anterior knee pain, since fortuitous pathological findings are frequent.

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Clinical Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction for Patellar Instability Among Patients With Trochlear Dysplasia

The American Journal of Sports Medicine ◽

10.1177/0363546517745625 ◽

2018 ◽

Vol 46 (4) ◽

pp. 883-889 ◽

Cited By ~ 25

Author(s):

Joseph N. Liu ◽

Jacqueline M. Brady ◽

Irene L. Kalbian ◽

Sabrina M. Strickland ◽

Claire Berdelle Ryan ◽

...

Keyword(s):

Patellar Instability ◽

Ligament Reconstruction ◽

Medial Patellofemoral Ligament ◽

Trochlear Dysplasia ◽

Patellofemoral Instability ◽

Mpfl Reconstruction ◽

Trochlear Groove ◽

Return To Sports ◽

Medial Patellofemoral Ligament Reconstruction

Background: Medial patellofemoral ligament (MPFL) reconstruction has become one of the most common and widely used procedures to regain stability among patients with recurrent lateral patellar dislocation. While recent studies demonstrated low recurrence rates, improved patient-reported outcome measures, and a high rate of return to sports, limited literature explored its effectiveness as an isolated intervention in the context of trochlear dysplasia. Purpose: To determine the efficacy of isolated MPFL reconstruction in treating patellar instability in the setting of trochlear dysplasia. Study Design: Case series; Level of evidence, 4. Methods: This was a retrospective review of consecutive patients who underwent uni- or bilateral medial patellofemoral ligament reconstruction for patellofemoral instability with a minimum 2-year follow-up. No osteotomies were included. Pre- and postoperative assessment included ligamentous laxity, patellar crepitus, tilt, translation, apprehension, and radiographic features, including tibial tubercle-trochlear groove (TT-TG) distance, Dejour classification, and Caton-Deschamps index. Results: A total of 121 MPFL reconstructions were included. Mean age at surgery was 23.8 years, and 4.4 dislocation events occurred before surgery. Mean follow-up was 44 months; 76% of patients were female. Mean preoperative TT-TG ratio was 13.5, and mean Caton-Deschamps ratio was 1.2; 92% of patients had Dejour B, C, or D trochlear dysplasia. Kujala score improved from 55.0 preoperatively to 90.0 ( P < .001). Almost all patients (94.5%) were able to return to sports at 1 year, with 74% returning to the same or higher level of play. Only 3 patients reported a postoperative dislocation or subluxation event. Discussion: For patients without significantly elevated TT-TG distances or significant patella alta, isolated MPFL reconstruction provides a safe and effective treatment for patellofemoral instability, despite the presence of trochlear dysplasia. Most patients are able to return to sports by 1 year postoperatively at the same or higher level of play.

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Effect of Trochlear Dysplasia on Commonly Used Radiographic Parameters to Assess Patellar Instability

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120938760 ◽

2020 ◽

Vol 8 (7) ◽

pp. 232596712093876

Author(s):

J. Lee Pace ◽

Chris Cheng ◽

Sheeba M. Joseph ◽

Matthew J. Solomito

Keyword(s):

Risk Factors ◽

Patellar Instability ◽

Trochlear Dysplasia ◽

Inverse Correlation ◽

Trochlear Groove ◽

Modified Technique ◽

Significant Inverse Correlation ◽

Patellar Tilt ◽

Level Of Evidence ◽

The Relationship

Background: Trochlear dysplasia (TD) is an important anatomic risk factor for patellar instability (PI). Several imaging-based risk factors for PI have been established, but it is unclear what effect TD has on these measurements, and the Dejour method of categorizing TD has been shown to be unreliable. The lateral trochlear inclination (LTI) is a quantifiable measurement of proximal trochlear morphology. Recently, a modified technique for measuring LTI referencing the posterior condylar angle has demonstrated near-perfect reliability and may serve as a new standard for quantifying TD. Purpose/Hypothesis: The purpose of this study was to evaluate how TD, expressed in terms of LTI, affects historically used measures of PI, including the sulcus angle (SA), tibial tuberosity to trochlear groove (TT-TG) distance, lateral patellar inclination (LPI), and Caton-Deschamps (CD) ratio. We hypothesized that lower LTI (ie, more dysplastic trochlea) will correlate with higher SA and TT-TG distances, increased patellar tilt, and more patella alta. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients aged 9 to 18 years treated for PI between January 2014 and August 2017 were queried. On magnetic resonance imaging (MRI), LTI, SA, LPI, and the TT-TG measured at the most proximal (pTT-TG) and distal (dTT-TG) aspects of the fully formed trochlear groove were measured on axial images. CD ratio was measured using sagittal MRI as well as lateral radiographs. All measurements were performed by 2 independent observers. Patients were included if there was a diagnosis of PI that was confirmed with a chart review and if there were appropriate imaging studies to analyze. Results: A total of 65 patients met inclusion criteria for this study. Average pTT-TG distance (15.7 ± 4.5 mm) was not significantly different from dTT-TG distance (15.7 ± 4.2 mm) ( P = .94). LTI had a weak but significant inverse correlation with pTT-TG ( r = –0.40; β = –0.15 mm; P < .001) and SA ( r = –0.43; β = –0.478°; P < .001). There was a moderate and significant inverse correlation of LTI with dTT-TG ( r = –0.593; β = –0.21 mm; P < .001) and with LPI ( r = –0.69; β = –0.54°; P < .001). There was a weak but significant correlation between LTI and the MRI-based CD ratio ( r = 0.279; β = 0.149; P = .005). Radiograph-based CD ratio did not show a significant correlation with LTI ( r = –0.189; P = .135). Conclusion: Smaller (ie, more dysplastic) LTI values correlated significantly with larger TT-TG, SA, LPI, and MRI-based CD ratio measurements. The relationship between SA and LTI is intuitive, but the relationship between LTI and the other analyzed variables suggests that they are dependent variables to TD and may not be consistent independent risk factors for PI. Together, these suggest that TD alters the radiographic interpretation of TT-TG and patellar tilt. The correlation between TD and patellar height is unclear and warrants further investigation.

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Relationship Between Patellar Morphology and Known Anatomic Risk Factors for Patellofemoral Instability

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120988690 ◽

2021 ◽

Vol 9 (3) ◽

pp. 232596712098869

Author(s):

Andrew E. Jimenez ◽

Benjamin J. Levy ◽

Nathan L. Grimm ◽

Steven M. Andelman ◽

Chris Cheng ◽

...

Keyword(s):

Regression Analysis ◽

Trochlear Dysplasia ◽

Cruciate Ligament ◽

Patellofemoral Instability ◽

Cross Sectional Study ◽

Adolescent And Young Adult ◽

Level Of Evidence ◽

Cross Sectional ◽

Mri Scans ◽

Patellar Morphology

Background: Patellar instability (PI) is a common problem among pediatric, adolescent, and young adult patients. Recent literature has shown a correlation between pathoanatomy and PI. Purpose/Hypothesis: The purpose of this study was to determine if there is any difference in patellar shape in patients with and without PI and if there is any association between the shape of the patella and the shape of the trochlea. Our hypothesis was that there would be no association between the shape of the patella and the likelinhood of having PI and that the shape of the trochlea would not be associated with patellar morphology. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance imaging (MRI) scans were analyzed for 97 study patients with PI and 100 control patients with anterior cruciate ligament tears. Radiologic measurements of trochlear morphology were collected via MRI; 15 measurements of patellar morphology were then measured using axial MRI scans. Comparisons between the control and PI groups were performed using a 2-tailed t test. Regression analysis was performed to determine if associations existed between the 15 patellar morphology measurements and the trochlear dysplasia measurements. Results: There were no statistically significant differences between the PI and control groups for the majority of patellar morphology measurements. With regression analysis, there were no statistically significant associations between the majority of patellar morphology measurements and the trochlear dysplasia measurements. Conclusion: Patellar morphology is highly variable in knees with and without PI. There was a minimal association between measurements of patellar morphology and trochlear dysplasia.

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What sports medicine practitioners should know about imaging for femoro-patellar pathologies

Sports & Exercise Medicine Switzerland ◽

10.34045/sems/2020/2 ◽

2020 ◽

Keyword(s):

Risk Factors ◽

Knee Pain ◽

Anterior Knee Pain ◽

High Reliability ◽

Trochlear Dysplasia ◽

Trochlear Groove ◽

Clinical Imaging ◽

Adequate Treatment ◽

Patellar Maltracking ◽

Anterior Knee

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Patients with different patellofemoral disorders display a distinct ligament stiffness pattern under instrumented stress testing

Journal of ISAKOS Joint Disorders & Orthopaedic Sports Medicine ◽

10.1136/jisakos-2019-000409 ◽

2020 ◽

Vol 5 (2) ◽

pp. 74-79

Author(s):

Ana Leal ◽

Renato Andrade ◽

Betina Hinckel ◽

Marc Tompkins ◽

Ricardo Bastos ◽

...

Keyword(s):

Risk Factors ◽

Stress Testing ◽

Case Series ◽

Patellofemoral Instability ◽

Displacement Curve ◽

Trochlear Groove ◽

Lateral Tilt ◽

Patient Reported ◽

Ligament Stiffness ◽

Force Displacement

ObjectiveInvestigate the patellar force-displacement profile (ligament stiffness) of patellofemoral disorders.MethodsFifty-two knees from 34 consecutive patients (mean 31.6 years and 53% male) were analysed including 24 knees with patellofemoral pain (PFP), 19 with potential patellofemoral instability (PPI) and 9 with objective patellofemoral instability (OPI). Physical examination, patient-reported outcome measures (Kujala and Lysholm Scores), standard radiography and MRI or CT were performed in all patients. Instrumented stress testing (Porto Patella testing device) concomitantly with imaging (MRI or CT) was performed to calculate ligament stiffness.ResultsThe force-displacement curves in patients with PPI and OPI displayed a similar pattern, which was different from that of the PFP group. Patients with PPI showed higher ligament stiffness (a higher force was required to displace the patella) than the patients in the OPI group. Patients with OPI had a statistically significant shallower trochlear groove and increased lateral tilt. More than half of the PPI and OPI population presented with at least one classic risk factor (patella alta, trochlear dysplasia, increased quadriceps vector, lateral tilt). In the PPI group, at least two risk factors were found in 37% of patients, whereas at least 33% of patients in the OPI group had three risk factors present. None of the patients presented with all four anatomical risk factors.ConclusionPatients presenting with patellofemoral instability (PPI and OPI) display similar ligament stiffness patterns (force-displacement curve). Patients with PFP and PPI showed higher ligament stiffness as compared with patients with OPI.Level of evidenceLevel V, case series.

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