Femoral trochlear dysplasia is characterized by a shallow to absent femoral trochlea, a hypoplastic lateral femoral condyle, and a hypoplastic patella. Femoral trochlear dysplasia can lead to patellar instability, starting at approximately 20° of knee flexion when the patella begins to engage the trochlear groove.
What is trochlear dysplasia of the knee?
Trochlear Dysplasia FAQ. In most knees, there is a groove on the end of the femur, called the trochlea, in which the kneecap sits. This provides a certain amount of bony stability to the kneecap joint to prevent it from sliding, mainly to the outside.
How is dysplasia of the femoral trochlea diagnosed?
Dysplasia of the femoral trochlea can be diagnosed reliably by using quantitative or qualitative criteria on midsagittal or transverse MR images obtained 3 cm above the femorotibial joint space. Femoral trochlear dysplasia: MR findings Radiology. 2000 Sep;216(3):858-64.doi: 10.1148/radiology.216.3.r00se38858.
What does trochlear dysplasia look like on Xray?
Symptoms of trochlear dysplasia: On plain X-rays, one can see a “crossing sign” on the lateral knee X-ray that would indicate that the trochlea groove is both flat and shallow. The 45-degree patella X-ray would also show a decrease in size of the groove, flattening, and sometimes a dome shape.
What is the treatment for trochlear dysplasia?
Treatment of Trochlear Dysplasia. The treatment of trochlear dysplasia can be very difficult. It is important to have a thorough workup to include a patient’s overall alignment, their tibial tubercle–trochlea groove angle (TT–TG), and an MRI scan to evaluate the status of the articular cartilage of their patellofemoral joint.
How to diagnose trochlea dysplasia?
How to treat trochlear dislocation?
What is the X-ray of a trochlear groove?
What is it called when the kneecap is flat?
What is the patella of the knee?
Why is it important to have a plain X-ray of the patella alta?
Why is the patella important?
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How do you fix Trochlear dysplasia?
Trochleoplasty is a surgical procedure to treat a condition called trochlear dysplasia, where the trochlear groove is abnormally shaped, causing the patella (kneecap) to slip out of the groove or dislocate.
What is femoral Trochlear?
The trochlea of femur (femoral trochlea) is the cranial cartilaginous part of distal femur, for articulation with the patella fo form the femoral patellar joint. It consists of a groove bounded by the medial and a lateral ridges.
How do you fix knee dysplasia?
The only way to 'cure' it is to perform a patellofemoral resurfacing arthroplasty (a partial knee replacement), but this is a fairly major op that involves putting in an artificial joint, and this is normally reserved only for older patients and/or patients with severe symptoms and severe damage.
Is Trochlear dysplasia painful?
Trochlear dysplasia also causes knee pain during activities that involve bending the knee such as walking up or down the stairs or running. In the long term, the abnormal movement of the patella on the femur can lead to the development of wear and tear of your joint surface known as osteoarthritis.
Is Trochlear dysplasia serious?
Severe cases of trochlear dysplasia are rare, whereas more mild cases where the trochlear groove may be flatter than normal, are not that uncommon. Therefore, it is a relatively common condition, but often does not cause significant problems when it is a milder case of trochlear dysplasia.
Do you need surgery for Trochlear dysplasia?
Dr. Welch recommends non-surgical management for most patients with trochlear dysplasia. A dedicated physical therapy program is a very important part of the treatment plan. Physical therapy focuses on strengthening of the core muscles, hip muscles, as well as the quadriceps to help stabilize the patella.
How many people have Trochlear dysplasia?
Knees with high-grade trochlear dysplasia based on the sulcus angle were 11 times more likely to have had previous patellar instability (p = 0.013). Conclusions: The prevalence of high-grade trochlear dysplasia in the general population is approximately 10%, and there may be an association with patellar instability.
Where is the femoral trochlea located?
The femoral trochlea is a key portion of the knee's patellofemoral joint. The knee is a juncture where the upper and lower leg meet, and is one of the most complicated joint systems in the body.
Is a Trochleoplasty major surgery?
Though this is a widespread treatment for recurrent patella instability, open trochleoplasty is a highly invasive procedure and leads to an increased risk of infection, scar tissue, and pain.
Is Trochlear dysplasia a disease?
TD is not a disease and most individuals who have this abnormality, are asymptomatic and as such, TD is a condition. The higher the degree of TD, the higher the risk of becoming symptomatic is, either by patellofemoral instability (PFI), patellofemoral pain (PFP) or patellofemoral osteoarthritis (PF OA).
Is Trochlear dysplasia congenital?
Trochlear dysplasia is characterized by abnormal trochlear morphology and a shallow groove. It is associated with recurrent patellar dislocation, but it is unclear whether the dysplasia is congenital, the result of lateral tracking and chronic instability, or caused by a combination of factors.
How is Trochlear dysplasia measured?
The Dejour classification of trochlear dysplasia is assessed using lateral knee radiographs as well as axial CT or MRI imaging to evaluate abnormal trochlear morphology. The classification is based on the presence of the crossing sign, a supratrochlear spur, and double contour sign on lateral radiographs [11, 13].
Where is the trochlea located?
In the human arm, the humeral trochlea is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch on the ulna in the forearm.
What is a trochlea in medical terms?
Medical Definition of trochlea : an anatomical structure resembling a pulley: as. a : the articular surface on the medial condyle of the humerus that articulates with the ulna. b : the fibrous ring in the inner upper part of the orbit through which the tendon of the superior oblique muscle of the eye passes.
What is a Trochlear chondral defect?
A chondral defect refers to a specific, localized area of damage to the articular cartilage that lines the ends of the bones (like a tile missing in the floor). Articular cartilage is the coating of the bones and allows for smooth motion between the ends of the bones.
How common is Trochlear dysplasia?
Epidemiology. The reported prevalence of trochlear dysplasia in recurrent patellar dislocations is ~80% (range 74-85%) 1,15. The latter is most common in the adolescent age group 4,5.
Aspects of trochlear dysplasia
Trochlear dysplasia (TD) is an abnormality of the knees trochlear groove. There is an invisible transition between what is normal and what is pathologic. The knees trochlear groove is the guide channel, into which the patella engages and glides.
Heredity or origin or aetiology to TD
Larger apes have a flat trochlea 27, however, since humans are walking upright, we have become a little knock-kneed, as this brings the knee joints closer together and assists the upper body to be positioned above the centre of gravity for walking.
Closing remarks on TD
Another important point of issue is the trochlear difference of cartilage and bone configuration, also denominated cartilage/bone mismatch and that the cartilaginous sulcus angle is consistently higher than the underlying osseous sulcus due to thicker cartilage in the centre of the groove 13,62,65,66-68.
What is the prevalence of trochlear dysplasia?
The reported prevalence of trochlear dysplasia in recurrent patellar dislocations is ~80% (range 74-85%) 1,15. The latter is most common in the adolescent age group 4,5.
What is the term for a deformity of the femoral trochlea?
Trochlear dysplasia. Trochlear dysplasia refers to a dysplastic deformity of the femoral trochlea and is a known risk factor for patellofemoral instability.
What is a known association with patellofemoral instability?
Trochlear dysplasia is a known association with patellofemoral instability.
What imaging method is used to diagnose trochlear dysplasia?
Different radiographic methods exist to assess for trochlear dysplasia in true lateral radiographic images of the knee and cross-sectional imaging CT and MRI respectively.
What type of dysplasia is better after surgery?
The clinical outcome seems to depend on the type of dysplasia and seem to show better results after surgical correction of Dejour type B and type D dysplasia.
What is the bump in the distal femur?
trochlear bump: the increased distance between the anterior trochlear groove and extension of the anterior cortex of the distal femur
Is trochlear dysplasia a predisposing factor?
Trochlear dysplasia is a predisposing factor of patellofemoral instability and should be only treated in that context.
What is the prevalence of trochlear dysplasia?
The reported prevalence of trochlear dysplasia in recurrent patellar dislocations is ~80% (range 74-85%) 1,15. The latter is most common in the adolescent age group 4,5.
What is the term for a deformity of the femoral trochlea?
Trochlear dysplasia. Trochlear dysplasia refers to a dysplastic deformity of the femoral trochlea and is a known risk factor for patellofemoral instability.
What is a known association with patellofemoral instability?
Trochlear dysplasia is a known association with patellofemoral instability.
What imaging method is used to diagnose trochlear dysplasia?
Different radiographic methods exist to assess for trochlear dysplasia in true lateral radiographic images of the knee and cross-sectional imaging CT and MRI respectively.
What type of dysplasia is better after surgery?
The clinical outcome seems to depend on the type of dysplasia and seem to show better results after surgical correction of Dejour type B and type D dysplasia.
What is the bump in the distal femur?
trochlear bump: the increased distance between the anterior trochlear groove and extension of the anterior cortex of the distal femur
Is trochlear dysplasia a predisposing factor?
Trochlear dysplasia is a predisposing factor of patellofemoral instability and should be only treated in that context.
Why is trochlear dysplasia so daunting?
The study of trochlear dysplasia can be daunting, first because it deals with a three-dimensional surface whose biomechanics may not be self-evident. Second, in an attempt to quantify the complexities of this surface, researchers over the years have created a large number of metrics that may be difficult to remember. Finally, different authors have employed metrics that initially may seem identical but are not, related to variations in methodology that can significantly affect results.
How to correct trochlear dysplasia?
Trochlear dysplasia can be corrected using surgery. The earliest operative technique that enjoyed widespread adoption was described in 1915 by Albee, 26 who performed a coronally-oriented opening osteotomy of the lateral femoral condyle to steepen the inclination of the lateral trochlea without changing the trochlear floor (Figure 14). This approach seems to disregard the apparent cause of most cases of trochlear dysplasia—namely, that it is the trochlear floor that is too elevated, not the condyles that are too flat. Because the procedure tends to lift the patella further away from the femur, narrowing the angle between the vectors of the quadriceps and patellar tendons, it elevates contact pressures and predisposes to cartilage damage. 27
What is patellar tracking?
Simplified schematics of patellar tracking. In these schematics, the curved femoral condyles are flattened into a planar surface. In a normal trochlea (a), the patella (sphere), guided by forces from the quadriceps tendon, patellar tendon, and medial and lateral supporting structures (red arrows), begins each cycle of knee flexion by entering the shallowest, most proximal portion of the trochlea (upper portion of diagram). In a dysplastic trochlea, the crucial proximal extent of the trochlea may be (b) flat or (c) convex, predisposing to patellar dislocation. Other factors contributing to patellar instability can similarly be conceptualized as alterations of the positions and forces illustrated in this figure.
What is the crossing sign of trochlear dysplasia?
The most fundamental sign of trochlear dysplasia, the crossing sign is positive when the contours of the trochlear floor and of the lateral femoral condyle intersect at any level. This indicates that, at that level, the lateral side of the trochlea is flat or, equivalently, the trochlear floor is flush with the lateral condyle.
What is the difference between a normal trochlea and a normal trochlea?
Whereas a normal trochlea (also known as facies patellaris, intercondylar groove, or intercondylar sulcus) is sufficiently concave to guide and retain the patella throughout the normal range of movement, a dysplastic trochlea may be shallower than normal or even flat or convex, thus predisposing the patella to lateral subluxation or even dislocation.
How to measure trochlear depth?
(a) To make this measurement, the tangent to the posterior aspect of both condyles (green line) is first drawn as a reference baseline. Perpendicular to this baseline, measurements are made to the most anterior points of the medial and lateral facets (red lines), as well as to the trochlear floor (blue line). To compute the final metric, the floor measurement is subtracted from the average of the two facet measurements. The average of the two facet measurements may be interpreted as the length of a line parallel to and equidistant from the two facet measurements (red dotted line). (b) Applying these measurements to the appropriate cross-section of our introductory case yields a trochlear depth of (61.3+63.6)/2 − 61.0 = 1.4 mm, which is abnormally small.
Where is trochlear depth measured?
The trochlear depth is measured at a location in the proximal aspect of the trochlea that requires the construction of multiple lines (Figure 7a). Henri Dejour et al. considered this measurement to be pathologic at a value of 4 mm or less.
What is the term for the engagement of the trochlea into the trochlea?
Patella alta (engagement into the trochlea does not occur in the early phase of knee flexion, thus potentiating instability at the patellofemoral joint)
How to diagnose patellar instability?
Patellar instability is normally diagnosed through a comprehensive history of the patient's symptoms and functional objective assessment of the knee. Further scans such as MRI's and Ultrasound imaging can be performed to rule out any structural deficits. Patellofemoral instability can also be examined through a lateral radiography or CT scan. In the case of trochlea dysplasia, medical images show different flexion angles and varus movements are limited in the knee. CT scans provide better images than MRI scans. A lateral radiography can provide information about the height of the patella and whether there is trochlea dysplasia.
What are the three ligaments that are on the medial side of the patella?
The medial side exists of three ligaments: The medial patellofemoral ligament (MPFL), the patellomeniscal ligament (MPML) and patellotibial ligament (MPTL): These are the primary ligamentous structures constraining lateral movement of the patella, the MPFL is the most important one. The MPFL is a continuation of the deep retinacular surface ...
What causes patellofemoral instability?
Patellofemoral instability is a result of malalignment of the patella in the trochlear grove caused by stretched or ruptured medial kneecap-stabilizers (traumatic) or anatomical anomalies of the knee joint. Primarily a conservative, non-operative exercise treatment is initiated, where quadriceps muscle strengthening is the main objective. Nearly half of all patients with a first-time dislocation will suffer additional dislocations. Chronic instability of the patellofemoral joint and recurrent dislocation may lead to progressive cartilage damage and severe arthritis if not treated adequately. In those cases, one can opt for operative intervention. The post-operative physical therapy treatment depends on the type of surgery that has been performed.
What age do you have to be to have a kneecap dislocation?
Traumatic kneecap dislocation is typically the result of a sports injury and about 2/3 of the cases occur in young, active patients under the age of 20. In case of traumatic dislocation conservative management may be preferred although nearly half of all patients with a first-time dislocation will suffer additional dislocations. Subjects may even develop patellar instability, (aspecific) pain, patellofemoral arthritis or even chronic patellofemoral instability, depending on the presence and severity of the anatomic damage.
How does patellofemoral instability develop?
There are two ways to develop patellofemoral instability by dislocation of the patella. It can develop after a traumatic dislocation of the kneecap in which the medial kneecap-stabilisers are stretched or ruptured, which eventually can result in recurrent dislocations of the patella.
What causes knee pain and knee disability?
Definition/Description. A frequent cause of knee pain and knee disability is patellofemoral instability. Patellofemoral instability can be defined in different ways. One way is when the patient has undergone a traumatic dislocation of the patella.
How to diagnose trochlea dysplasia?
A diagnosis of trochlea dysplasia is usually made by a thorough physical exam and radiographic work-up. Patients with trochlear dysplasia often have increased medial and lateral patellar translation near full extension and at 45 degrees of knee flexion. They may also have an apprehension test where they feel their patella is going ...
How to treat trochlear dislocation?
Because the severity of trochlea dysplasia can run from minor to severe, treatment options are also varied. They can include a reconstruction of the medial patellofemoral ligament, a tibial tubercle osteotomy, a trochleoplasty, where the distal aspect of the femur is cut and reshaped to create more of a normal groove, a distal femoral osteotomy, and other associated treatments. Thus, no one patient has the same treatment as another, and a thorough workup is necessary to determine the best course of action, if any, for a particular patient with trochlear dysplasia.
What is the X-ray of a trochlear groove?
X-ray demonstrating the flatter curvature of the trochlear groove which is present with trochlear dysplasia. Patients with significant trochlear dysplasia are at a much higher risk of having their kneecap re-dislocate after an initial dislocation.
What is it called when the kneecap is flat?
When the trochlea is flat, or even possibly has a convex or dome shape, it is known as trochlear dysplasia which usually is referred to as an unstable kneecap. In these circumstances, the trochlea is not shaped normally, and the patella does not have the normal bony constraints to provide stability. Thus, one needs to rely on the medial patellofemoral ligament and their quadriceps mechanism to hold the patella in place.
What is the patella of the knee?
This area of the knee is easy to identify. When the knee is bent, the undersurface of the kneecap (the patella) lies in an area known as the trochlear groove. The sides of the patella and the walls of the groove should be almost parallel. The normal shape of the trochlea groove is concave. In fact, the outside, or lateral aspect of the trochlea groove has a higher bump than the inside part. This allows the patella, or kneecap, to glide down the central aspect of the distal femur rather effortlessly due to its bony constraints. This is important because the patella serves as a fulcrum to increase the overall strength and efficiency of the quadriceps muscles of the thigh.
Why is it important to have a plain X-ray of the patella alta?
This is important because surgical treatments may not always be indicated if there is significant arthritis present. In addition, a plain X-ray to look at the amount of patella alta, or a high-riding patella, is indicated. The treatment of trochlear dysplasia can be very difficult.
Why is the patella important?
This is important because the patella serves as a fulcrum to increase the overall strength and efficiency of the quadriceps muscles of the thigh. When the trochlea is flat, or even possibly has a convex ...
Epidemiology
Diagnosis
- The diagnosis of trochlear dysplasia is usually established by typical imaging features. Since cross-sectional images and radiographs show different aspects of trochlear dysplasia it might be worthwhile acquiring both if there are doubts.
Clinical Presentation
- Patients usually present with recurrent lateral patellar dislocation and patellofemoral instability.
Pathology
- Trochlear dysplasia can involve a shallow, flattened or convex trochlear groove +/- a hypoplastic (small) or convex lateral femoral condyle 15. This dysplastic deformity of the most superior aspect of the femoral trochlea, in particular, is a risk factor for patellar dislocation during the transition from full knee extension to early knee flexion. ...
Radiographic Features
- Different radiographic methods exist to assess for trochlear dysplasia in true lateral radiographic images of the knee and cross-sectional imaging CT and MRI respectively. The classification of trochlear dysplasia as described by Dejour 6,13 requires the correlation of three radiographic signs from lateral knee radiographs with cross-sectional imaging 16. 1. type A: crossing sign, no…
Radiology Report
- There is a poor correlation between the classical and still commonly used Dejour classification system and the measurements derived from axial MR images. This should be taken into account when indicating trochlear dysplasia. The radiological report should, therefore, contain a qualitative description as well as the metric used for the diagnosis of trochlear dysplasia.
Treatment and Prognosis
- Trochlear dysplasia is a predisposing factor of patellofemoral instabilityand should be only treated in that context. The treatment of high-grade trochlear dysplasia is trochleoplasty, which aims at correcting the trochlear depth abnormality by recreating a centralized groove, which facilitates the entry of the patella during early knee flexion. In symptomatic patients with recurre…
Practical Points
- The need for a simplified approach in respect to grading of trochlear dysplasia assessed on MR images has been formulated and a simplified grading into low-grade and high-grade trochlear dysplasia has been proposed 9. This is also due to a poor correlation with the original Dejour classification system 9, which is considered to be difficult to understand 15. A review regarding …