The knee joint is the largest joint in the human body. It is a complex joint connecting the femur and tibia. The joint is formed by the navicular bone in the form of the patella, which, next to the tendon and quadriceps muscle of the thigh, and the patella ligament, forms the knee extension apparatus. In people with normal anatomical structure, the patella is located within the femoral block and forms the patellofemoral joint with it. Due to the high forces transmitted by the knee, its articular capsule is reinforced with many ligaments, and additional stabilization is provided inside the joint by: cruciate ligaments and menisci.
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Patellar dislocation - what is it?
Patellar dislocation is an injury in which the kneecap protrudes from the intercondylar furrow. The knee joint is most prone to patellar dislocation at the moment of internal rotation of the thigh in relation to the foot set on the ground, as well as flexion and deformation of the knee with simultaneous strong tension of the quadriceps muscle. In this case, the kneecap dislocates in the lateral (outward) direction, often causing damage to the soft tissues of the knee area.
The second most frequent dislocation of the kneecap is caused by someone else hitting the medial part of the kneecap, causing it to dislocate laterally.
In the diagnosis, follow-up and prognosis after an injury, it is absolutely essential to determine the patient's possible primary predisposition to recurrence of the injury. This is a key and most often ignored fact in basic diagnostics.
Patellar dislocation very rarely occurs in people with a properly shaped knee joint, regardless of the injury mechanism. These patients also have a high probability of planning a quick and safe rehabilitation treatment and they will not require surgery.
In people with various types of primary disorders, the most common of which are: high position of the patella, shallow block of the femur, increased internal torsion of the femur, lateral position of the tibial tuberosity, high index TT-TG (Tibial Tuberosity - Trochlear Groove Distance), valgus knees, elastopathy, it is much easier to develop primary and subsequent dislocations of the patella. In this case, there is a very small chance that the rehabilitation treatment itself will prevent further dislocation of the kneecap - the so-called development of recurrent dislocation of the patella.
During dislocation, damage to the kneecap or lateral condyle occurs relatively often (during dislocation or setting of the kneecap). In addition, in virtually every case, the ligament that runs from the femur to the patella, which supports it from the medial side, is damaged, i.e. the medial patellar ligament (MPFL - Medial Patello Femoral Ligament).
Patellar dislocation does not remain indifferent to the knee joint. Underestimating the injury or improper treatment and improper rehabilitation may lead to complications in the future, such as:
recurrent or habitual dislocations of the patella,
patellar chondromalacia,
degenerative disease of the patellofemoral joint,
atrophy of the quadriceps muscle of the thigh.
Patellar dislocation - symptoms
Symptoms that we will observe after the injury include: severe pain, the patellar bone jump to the side of the knee joint and the painful blockage of the knee movement (the patient is not able to bend and straighten the knee within the physiological range of motion). The deformation of the contour of the knee at the front is also visible. Often the kneecap may turn on its own. Secondary trauma may lead to intra-articular bleeding and edema. If the kneecap is set spontaneously, it is very difficult for the doctor in the Emergency Room to perform additional examinations (minimum ultrasound of the knee and sometimes MRI of the knee) that the patient has dislocated. The lack of correct diagnosis results in incorrect patient management after the injury.
The main and most severe symptom in patients with a history of dislocation of the kneecap, but without proper treatment, is pain and the feeling of subluxation of the patella, described in various ways. This pain may come on suddenly, may occur periodically and may change in severity. It can also be spilled and difficult to locate.
In addition, pain occurs after exertion and repeated alternating knee extension and flexion movements (running is an excellent example of this type of movement).
Patellar dislocation - diagnosis
In post-traumatic diagnostics, after a thorough clinical examination, which is sufficient to diagnose a dislocation, the remaining extended diagnostics should be performed, which is to show the consequences of a dislocation of the patella.
For imaging examinations, first of all, X-rays of both knee joints should be taken in three projections (AP + lateral projection + Merchant's projection) in order to exclude any detachment of the chondro-bone fragment from the medial surface of the patella or from the area of the lateral condyle. The absence of the detached bone-chondral fragment visible on X-ray does not exclude significant damage to the knee cartilage. To visualize this, an MRI of the knee is required.
If the patient is unable to bear the costs of an urgent MRI examination, then an examination that can also confirm such damage, but with less sensitivity is knee ultrasound - usually much cheaper and available immediately.
It is up to the patient and the doctor to decide whether to undertake conservative or surgical treatment after dislocation of the patella after individual diagnostics.
Patellar dislocation - conservative treatment
Conservative treatment is possible only when the cartilage or chondro-bone fragment in the joint has not been torn off.
Patellar dislocation for many years was improperly treated by puncture of the joint and immobilization of the limb in extension for a period of 4 weeks in a plaster splint. Patients treated in this way often never regained full fitness.
In recent years, after many studies, it has been shown that immobilizing the knee by putting on a plaster is the last thing that should be done in such a case.
The entire treatment procedure depends, of course, on the consequences of the dislocation itself, i.e. what structures in the joint have been damaged and to what extent. After such a serious injury, the knee will be painful and swollen for several days. It is also necessary to start rehabilitation as soon as possible, focusing on introducing the necessary movement in the knee joint within its safe range, in order to prevent the undesirable effects of immobilization in the orthosis and to accelerate proper tissue healing and strengthening the muscles essential for the knee, especially the medial muscles (voluminous muscle). medial, VMO), which plays a key role in keeping the kneecap in the correct position. If the injury has not resulted in damage to the bone elements, menisci and ligament damage, the knee joint may also be immediately stressed within the pain tolerance of the patient.
Patellar dislocation - surgical treatment
Before starting surgery for a patellar dislocation, you need to be aware of two goals:
removal of intra-articular damage, if it has occurred (urgent, early and necessary surgical treatment - knee arthroscopy);
restoring the kneecap to correct stability again in the femoral block (primary urgent, enabling early quick improvement without orthoses and careful slow rehabilitation, or postponed - in the case of recurrent, habitual instability).
Patella surgery is performed during knee arthroscopy combined with additional procedures on the ligamentous apparatus responsible for medial stabilization of the patella. In the case of pre-existing individual predispositions to dislocation of the patella (i.e. high position of the kneecap, lateral position of the tibial tuberosity, knee valgus, etc.), it is worth considering a procedure that will remove or correct it immediately.
Performing only arthroscopy and even MPFL repair in these cases, without the basic disturbances of the knee axis, will certainly not cure the instability permanently. During treatment after surgery, the most important role is played by properly selected physiotherapy. Postural and dynamic analysis of the patient's movement and exercises based on it are the key to a quick recovery.
Arthroscopic plasty of patellar instability, lateral release of the patella
Lateral release of the patella is a surgical procedure that involves cutting the patellar straps if their contracture has occurred in the course of chronic instability of the patella. Patella straps are nothing more than a network of thin ligaments running in the side part of the knee joint capsule, some of them also reach the iliotibial band. Arthroscopic plasty of patellar instability as a stand-alone operating procedure should rather not be performed. As a rule, it is an addition to the reconstruction of the patellofemoral ligament (MPFL) or the transfer of tibial tuberosity (TTT - Tibial Tuberosity Transfer).
Percutaneous minimally invasive correction of patellar instability, dislocating patella - duplication of the medial joint bag
Percutaneous minimally invasive correction of patellar instability can be performed as a duplication procedure, i.e. duplication of the joint bag - under the control of an arthroscope inserted into the knee joint. Stitches leading to the doubling of the joint bag at the site of the MPFL ligament are placed from small point accesses. This procedure is not recommended in case of high instability with massive MPFL damage and in patients with the so-called elastopathy, in which the scar site will loosen again after the duplication.
Another minimally invasive, percutaneous but much stronger permanent stabilization method is MPFL reconstruction with the use of an anchor with non-absorbable threads. It is inserted either into the kneecap or into the bone at the MPFL anatomical attachment site. Performing such an operation up to 2 weeks after the injury allows for fairly early and rapidly progressing rehabilitation without the need to immobilize the knee in an orthosis).
If necessary, both procedures described above can be combined with lateral release of the patella.
Surgical correction of patellar instability - reconstruction of the patellofemoral ligament (MPFL) from the patient's own tissues
Medial Patello-Femoral Ligament (MPFL) is the main ligament that passively stabilizes the patella, and its damage causes patellar instability, therefore it is very important to reconstruct this structure.
MPFL reconstruction is performed under arthroscopic guidance. After preparing the operating field, we collect either a part of the patellar ligament, or a part of the quadriceps tendon or another tendon - most often the tendon of the slender muscle, which requires additional surgical access and drilling additional bone channels in the patella. Compared to the procedures described above, these procedures are longer, more traumatizing and require longer and very careful rehabilitation. During them, we drill 4mm - 7mm canals in the femur and in the patella in the case of the slender muscle tendon.
After this procedure, the tissues and skin are sutured and a dressing is placed on the knee. In further treatment, it is important, as always, to implement targeted rehabilitation
World literature describes several dozen different concepts of MPFL reconstruction, including the use of completely artificial ligaments and many others. It is important to individually select the least traumatizing one for a given patient and ensuring that it will restore the kneecap stability - different in a slim woman working in the office and different in a 90-kilogram "rugby player" focused on early heavy loads.
Full reconstruction of patellar instability in the case of low or high patella with Tibial Tuberosity Transfer (TTT)
The procedure of full reconstruction of patellar instability in the case of low (very rare pathology) or high patella begins with arthroscopic inspection of the joint. During arthroscopy, first of all, the condition of the patellar cartilage surfaces and the intercondylar sulcus are assessed, and other lesions are treated.
Then a 6 cm cut is made medially from the tibia tuberosity. On the basis of previous MRI calculations, the decision is made on the cutting plane, direction and size of the target displacement of the tibial tuberosity along with the patellar ligament. Most often, we perform the procedure of lowering the tuberosity by 6 mm - 10 mm with a simultaneous shift of it forward (which reduces the sticking of the patella) and medially. After stabilizing the shifted tuberosity of the tibia with the use of titanium screws, arthroscopic and clinical examination of the position of the kneecap is performed. We make a decision about the need for any additional procedures - i.e. MPFL reconstruction or lateral release. In such a complex correction it is impossible to accurately predict before the procedure whether these procedures will be necessary after the transfer (TTT - Tibial Tuberosity Transfer).
With a good preoperative qualification, such a procedure protects the patient for life - not only against dislocation of the kneecap, but also against premature wear of the cartilage in the patellofemoral joint and related pain.
At this point, it is worth mentioning other indirect causes of dislocation and instability of the patella - knee valgus, increased torsion, and a shallow femoral block. Correction of these pathologies are, in short, procedures consisting in cutting the femur and restoring its correct axis in the frontal plane (so-called varus osteotomies or otherwise de-slackening) or rotation changes (so-called derotation osteotomes). In extreme cases, they must be combined with osteotomies of the tibia. In the case of a shallow block, the so-called arthroscopic trochleoplasty.
Rehabilitation after surgical treatment of a patellar dislocation
After surgical treatment, it is necessary to introduce targeted rehabilitation as soon as possible. After lateral release of the kneecap, transfer of tibial tuberosity or MPFL reconstruction, it is possible to introduce active knee bending and straightening movements in the greatest possible range of motion up to the pain limit in the first days after the procedure. In order to prevent pain, use cold compresses (thermogels, ice bags) and kinesiotaping therapy to control the hematoma and postoperative edema. In addition, mobilization of the kneecap is recommended to prevent the formation of adhesions around the kneecap and isometric exercises and exercises to strengthen the anterior group of the thigh muscles and other knee supports.
The most important element of rehabilitation after surgical treatment of a patellar dislocation is to increase the strength and endurance of the quadriceps muscle, especially its medial head, which is locally responsible for the control of the lateral slide of the patella (translation control). For this control to be correct, there should be an appropriate balance between the activation of VMO (Vastus Medialis - medial head) and the lateral head (VL - Vastus Lateralis), which involves activating VMO against VL during quadriceps contraction. In patients after dislocation of the patella and its surgical treatment, an incorrect VMO: VL activation ratio is found, therefore neuromuscular re-education to compensate for this deficit is a key point in physiotherapeutic treatment. In addition, you should focus on strengthening the VMO in terms of endurance and strength, because often, despite the correct timing, the VMO is too weak to adequately control the position of the kneecap in situations of increased load on the lower limb.
In addition to exercises to strengthen and improve the endurance of the anterior group of the thigh muscles, you should focus on training the muscles that control the pelvis and hip girdle (oblique abdominals and gluteal muscles) and on the hamstring training to improve the control of eccentric external rotation in the lower leg, which directly affects the correct axial load on the entire lower limb and its good stabilization.
The last tasks to be mastered in the postoperative rehabilitation of patellar dislocations are learning to walk with full load on the operated limb, obtaining the correct pattern of gait on various surfaces, climbing and descending stairs, and obtaining the correct deep feeling (prioprioception) of balance and coordination, which will allow the patient to 100% return to activities of daily living, work and sports without functional disorders and pain.
Important information
| Duration of the procedure (depending on the method) | 60 - 120 minutes |
| Tests required for surgery | basic - preparation for surgery tab |
| Anesthesia | subarachnoid |
| Hospital stay | 4 - 8 hours after surgery |
| A period of significant dysfunction | 2 - 4 weeks |
| A period of limited dysfunction | 5 - 12 weeks |
| Removal of stitches - first visit | 12 - 16 days after surgery |
| Change of dressings | every 3 - 4 days |
| Contraindications to the procedure | set individual |
Frequently asked questions about patellar dislocation
Patellar dislocation is an injury in which the kneecap protrudes from the intercondylar furrow. In order for dislocation to occur, there must be an additional cause (trauma) or pathology in the anatomy of the knee joint, which may include, among others, lateral positioning of the tibial tuberosity, bone development disorders (patellofemoral dysplasia), generalized joint laxity, previous knee injury , deformity of the foot or ante-thigh bone ante. The knee joint is most prone to patellar dislocation at the moment of internal rotation of the thigh in relation to the foot set on the ground, as well as flexion and deformation of the knee with simultaneous strong tension of the quadriceps muscle. In this case, the kneecap is most often dislocated laterally (outwards), often causing damage to the soft tissues of the knee joint area.
Surgical treatment of a patellar dislocation is the target treatment for recurrent (habitual) patellar dislocation and when it is damaged:
cartilage-bone fragment of the patella
medial patellar retinaculum,
cartilage surfaces
In the above cases, knee surgery is necessary, because leaving the unstable kneecap and not covering the resulting damage may consequently lead to inflammation of the patellofemoral joint with synovial swelling and numerous exudates, as well as destruction of the articular cartilage by abnormal abrasive forces.
The time of rehabilitation after surgery depends on the extent of the damage, the type of treatment procedures and the patient's level of activity. The use of arthroscopy allows for a significant reduction in postoperative pain, shortening the hospital stay and reducing the risk of postoperative complications and faster return of the patient to daily functioning.
After the surgical treatment of the patellar dislocation, full load on the operated limb, obtaining the correct gait pattern on a varied basis and obtaining the correct deep feeling (prioprioception) and 100% return to the activity of everyday life, work and sports without functional disorders and pain, is achieved just a few weeks after the performance arthroscopy.
