Dislocation of the kneecap in humans: treatment with surgery, how to correct the shift, symptoms and causes

Anatomical features of the knee joint

Anatomical structure of the knee joint
In order to understand exactly what pathological picture develops during the formation of a dislocated patella, it is necessary to know the basic anatomical and physiological aspects of the structure of the knee joint and the muscles surrounding it.

The patella is a small sesamoid bone located directly in front of the knee joint. It is located in the thickness of the tendon cord of the quadriceps femoris muscle, which is attached to the condyles of the tibia. Purely anatomically, the quadriceps tendon is located at the top of the patella, and at the bottom the kneecap is connected to its own patellar ligament.

On one outer side, the sesamoid bone is convex and loose, which provides it with good adhesion to the tendon fibers, and on the other inner side it is smooth and concave, which makes it possible to be mobile.

The mobility of the bone is very easy to check. Sit comfortably, stretch your legs forward so that your knee is completely straight (off). Now place your palm on your knee and press lightly. When you move your palm to the right or left, you can feel how it moves along with your hand.

The most stable position of the kneecap occurs when the position of the lower limb is formed with flexion of 140° or more.

The patella plays a very important role in the extension function of the lower limb. It will redistribute the center of application of force to itself from the femoral muscle, which greatly facilitates the entire work of the extensor system of the lower limb.

Essentially, the patella is the fulcrum of the lower leg, with the help of which it moves in space in relation to the knee joint.

Considering the importance of the patella in the functionality of the lower limb, it is not even worth talking about the need for proper treatment of any of its pathologies.

Habitual luxation of the patella

Habitual luxation of the patella. Treatment of habitual dislocation, diagnosis, complaints and rehabilitation after surgery.

Brief anatomical excursion

One of the main supports of the patella is the lateral femoral condyle. If you look at the joint in a flexion position at an angle of 135° in a tangential projection, the external condyle is located 1 cm higher than the internal one. This elevated position of the condyle protects the patella from external displacement.

Condylar dysplasia is believed to be one of the serious factors predisposing to dislocation. In practice, dysplasia is rare; imaginary dysplasia is more often observed due to some internal rotation of the femur, which neutralizes the increased position of the condyle.

Experts associate the development of habitual dislocation and the choice of surgery undertaken to eliminate it with the value of the Q angle. Normally, it is 11°. Angle Q can be considered as a template for the correct direction of action of the extensor apparatus.

With valgus deformity of the knee joint, the angle increases significantly, so such deformation is a factor predisposing to external dislocation of the patella. Valgus deformity in the subtalar joint creates internal rotation of the tibia, which significantly affects the stability of the patella.

The shape and size ratio of the patellar facets are important. Normally, the ratio of the sizes of the external and internal facets is 3:2, and as the size of the external facet decreases, the tendency to external displacement also increases.

The magnitude of the Q angle depends on the location of the tuberosity, and its later position should also be considered a factor predisposing to dislocation.

In addition to bone structures, soft tissue stabilizers play a leading role in the stable position of the patella. These include:

• CFM (quadriceps femoris muscle) - has a great impact on the patellofemoral joint. Not only the strength and elasticity of this muscle is important, but also the angles at which all four heads are attached in relation to the longitudinal axis of the limb.
• Internal oblique muscle of the thigh - the stability of the patella largely depends on the direction of its fibers, since the greater the angle of attachment of the fibers of this muscle to the inner edge of the patella, the stronger its role as a dynamic stabilizer.
• Medial patellomeniscal ligament – ​​provides almost 13% protection against shear forces.
• The medial patellotibial and patellomeniscal ligament complex is the most important secondary stabilizer of the patella.

Causes of habitual patellar luxation

• High position of the patella
• Dysplasia of the lateral femoral condyle
• Vastus internus muscle wasting
• Lateralization of the tuberosity
• Valgus joint deformity
• Hypertrophy of the external head of the quadriceps femoris muscle
• Generalized ligament laxity

Patient complaints

Typically, the patient reports several episodes of external dislocation (or subluxation), accompanied by acute pain, hemarthrosis and swelling of varying severity. Most patients experience a feeling of fear of the possibility of another relapse.

Diagnostics

Since congenital anatomical anomalies are almost always bilateral, it is necessary to examine both joints. It can be performed lying down, standing, sitting and while walking. While standing, it is easier to determine even a slight degree of valgus deformity, internal rotation of the hip, and foot deformities. While sitting, the strength of leg extension is checked, the position of the patella is established, and the Q angle can be measured.

When examining a patient, it is necessary to pay attention to the degree of mobility of the patella (“fear and anxiety test”), to identify or exclude hypotrophy of the vastus medalis, and crepitus during movements of the patella.

The “anxiety” test is positive when, when the patella moves to the edge of the lateral condyle, the patient experiences a feeling of fear about the possibility of a relapse and tries to stop the study.

The appearance of pain when resisting active extension of the leg, along with crepitus, indicates degenerative changes in the patella.

The tilt test is carried out in the position of full extension and relaxation of the femoral joint. The examiner lifts the outer edge of the patella by applying anterior to posterior pressure on the medial edge. The patella should not be displaced from the block.

Tests are performed in the supine position to determine superior, inferior, and lateral hypermobility of the patella. In the latter case, the patella should not move more than half its width.

An X-ray examination is required to detect condylar dysplasia, high position of the patella, and osteochondral fragments in the form of “chondromas.”

In addition to standard projections, various oblique views are recommended to evaluate the posterior surface of the patella, the angle of inclination, and obtain a horizontal image of the patella.

• Axial projection - it is possible to determine the pathological inclination of the patella outward, the condition of the cartilaginous surface of the patella, and the congruence of the patellofemoral joint.
• Lateral projection – determination of the high or low position of the patella, the depth of the intercondylar groove.

A standard anteroposterior radiograph is useful for assessing the position of the patella, the status of the centers of accessory ossification, and identifying degenerative changes in the femorotibial joint.

Treatment of habitual patellar luxation

For habitual dislocation of the patella, surgical treatment is indicated. There are more than 100 surgical techniques. The choice of surgical treatment method must be carefully planned and depends on the Q angle, the ratio of the length of the patella and its ligament, the presence and severity of degenerative changes in the patellar cartilage, and the age of the patient.

Rehabilitation

After the Krogius operation (combines external release with shortening of the medial section of the fibrous capsule), immobilization in a circular plaster cast or deep splint for 4-5 weeks is recommended. After the operation of transposition of the tibial tuberosity, the immobilization period increases to 6 weeks.

Causes of patellar dislocation

Patella dislocation
The cause of instability of the sesamoid bone is often several factors, which can be in combination or separately:

1. Underdevelopment of any anatomical elements of the knee joint. Usually the problem arises in early childhood, when the child begins to walk. There are several possible variants of knee joint dysplasia: underdevelopment of the femoral condyles, smoothing of the inner surface of the patella, displacement of the patella in relation to the knee joint due to ligamentous pathology, high position of the patella in relation to the joint.
2. Weakness of muscle tone in the thigh.
3. Weakness or chronic injury to the internal suspensory ligaments of the kneecap. Often this pathology occurs in athletes who lift and squat with high weights, but with proper preparation of the muscular system for the load, the pathology is rare.
4. Valgus rotation of the knee joint. This pathology is most often called X-shaped legs. There are degrees of severity of the process; the higher the degree, the higher the risk of developing patellar dislocation. This pathology can be corrected in the early stages with the help of physical activity, which will be aimed at training the leg muscles to maintain the correct location of the muscles and ligaments.

The combination of at least several of the above factors leads to chronic instability of the patella and can significantly reduce a person’s quality of life. Fortunately, corrective treatment has now been fully developed and you can easily get rid of all similar pathologies.

Description

The kneecap, or patella, is a small, oval-shaped bone that sits above the condyle of the femur at the front and top of the knee.
This bone is easily palpated at the front of the knee joint. The patella plays an essential role in walking and moving the knee joint and partially protects the ligament and other structures from damage. In the knee joint, during normal movement, the patella slides along the anterior surface of the femur and transmits force to the quadriceps femoris muscle. Mostly, patellar dislocation occurs in young people and adolescents, including especially often when participating in team sports. Usually, with certain impacts on the leg or with a blow to the side of the knee joint, the structures that support the patella are damaged. There is a displacement of the patella relative to the normal trajectory of movement - that is, dislocation or subluxation (outward displacement is more common). As a rule, the leg gives way and a sharp pain is felt in the knee joint. In most cases, the joint reduces on its own. If a dislocation or subluxation is repeated with minor loads, then this is considered habitual and can lead to instability of the patella.

The frequency of patellar dislocation varies, from 1-2 times a year to several times a day. This can provoke the development of patellofemoral arthrosis in the knee joint and, in addition, sharply reduces the quality of life.

Patella dislocation

Congenital dislocation of the patella
Conventionally, dislocations of the sesamoid bone can be divided into congenital and acquired or traumatic, which in turn are divided into lateral, torsional or vertical.

Classification of patellar dislocations:

• Congenital.
• Acquired or traumatic.

Lateral dislocation:

• Outer.
• Interior.

Torsion or rotation:

• Outer.
• Interior.
• Front.
• Vertical.

Lateral luxation of the kneecap is a pathological position that occurs when the sesamoid bone is displaced to the lateral (side) or medial (inner) side. External or lateral is more common.

Torsion or rotational dislocation is a pathological position that is characterized by rotation of the sesamoid bone around a vertical axis. This pathology is extremely rare, mainly after a car injury or a fall on the knee from a height.

Vertical dislocation is a pathological position that is formed when the tendon of the muscles of the anterior surface of the thigh and the patellar ligament itself are completely ruptured. The patella bounces up or down (depending on the level of damage to the tendon above or below the kneecap) due to muscle tone.

Diagnosis of dislocation

Photo: position of the patella
Diagnosis of any pathology in traumatology consists of several points that are important to perform in the correct sequence:

Anesthesia of the injury site. Instability of the patella is often accompanied by severe pain, which will interfere with examination and questioning of the patient. For diagnostic purposes, reflexes and sensation may be tested using neurological tests before pain relief.

1. Questioning the patient.
2. Examination of the patient.

Functional diagnostics, which consists of taking x-rays of the injured leg, computed tomography, and arthroscopy if necessary.

The diagnosis of patellar pathology according to the classification codes of the International Classification of Diseases, 10th revision (ICD-10) looks like this:

1. M22 Patella lesions.
2. Excluded: Patellar dislocation (S83.0).
3. M22.0 Habitual dislocation.
4. M22.1 Habitual subluxation.
5. M22.2 Disorders between the patella and the femur.
6. M22.3 Other disorders of the patella joints.
7. M22.4 Chondromalacia.
8. M22.8 Other lesions of the patella.
9. M22.9 Damage to the patella, unspecified.

Treatment of pathology

After treatment of a dislocation
Treatment of a dislocated patella consists of an integrated approach:

1. Anesthesia of the injury site.
2. Anti-inflammatory and anti-edematous therapy.
3. Restoring the integrity of damaged ligaments and muscles.
4. Immobilization of the limb to restore the integrity of the soft tissue at the site of injury. A plaster cast is often applied from the gluteal crease to the ankle joint, but with modern options, orthoses or other suitable means of rigid immobilization can be used.
5. Rehabilitation, which consists of physical exercises, physical therapy and massage.

Do not forget about such a concept as habitual dislocation of the patella, which occurs when the primary pathology of the patella is improperly treated.

Treatment

As a rule, with primary traumatic dislocation of the patella, conservative treatment is carried out; it is also possible with an imbalance of the internal and external retinaculum - in this case, treatment includes wearing a special patella, mobilization of the patella, and physical therapy. Surgical treatment is indicated when conservative treatment is ineffective or the patellar retinaculum fails. There are a large number of operations aimed at stabilizing the patella:

• transposition of the tibial tuberosity;
• soft tissue plastic;
• combined operations.

The choice of method of operation in each case is selected individually, because it depends on many factors. This disease can be treated conservatively in our clinic.

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