VII./3.: Patellofemoral impairments
In case of patellofemoral impairments the movements of the patella do not follow the sulcus on
the facies patellaris of the femur, and the patella subluxates or luxates.It may be caused by an
undeveloped femoral condyle, morphological and positional aberrations of the patella, possible
muscular contractures and ligament tear due to trauma. Consequential patellofemoral pain,
swelling, subluxation or luxation of the patella or patella hyperpression syndrome may occur and
may lead to degenerative changes in the patellofemoral joints.
VII./3.1.: Patella luxation and subluxation
The patella leaves the patellar sulcus of the femur during flexion-extension. We differentiate
between habitual, recurrent and congenital patella luxation. Etiology may differ, but risk factors
may be mutual (hypoplastic lateral femoral condyle, etc.).
VII./3.2.: Luxatio habitualis patellae
Luxatio habitualis patellae means that the patella luxates laterally during every flexion.
Dislocation of the patella is apparent, and palpable. It usually occurs between the ages 5-9, rarely
in older patients.
Etiopathology
It is the result of contracture of the femoral quadriceps muscle. The contracture may be congenital,
or the result of paralysis but it most commonly occurs in babies and small children following
injections usually antibiotics- given into the quadriceps femoris muscle. The fibrosis caused by the
injection leads to extension contractures in most cases and 1/5 of the patients develop patella
luxation.
Clinical symptoms
The patella slides off the lateral femoral condyle laterally every time the knee is flexed.
Figure 1.: The deformity of both bent knees is caused by the laterally luxated, well palpable patella.
On observation of the knee the slightly lateral position of the patella may be apparent, and we see
the patella slide off on the lateral side as the knee is bent, and then it may be palpated on the
lateral side, and we may see a sulcus appropriate for the facies patellaris of the femur. The
suprapatellar tendon is in a lateral position together with the patella, and we may palpate tension
in the vastus lateralis muscle and the iliotibial tract. The muscle tension is more apparent if we
bend the knee while fixing the patella in its normal position, thereby trying to prevent the luxation
In these cases we usually cannot flex the knee more than 30-40odegrees.
Wobbliness and retropatellar pain may occur. These children usually cannot meet sport and
physical education requirements for their age group.
Treatment
As the patella slides or bumps over the edge of the lateral femur condyle every time and the
cartilage may be damaged in time. This is why this impairment should be treated as soon as
possible.
Mutual step of the different surgical approaches are elongation of the quadriceps tendon, incising
the lateral capsule, and narrowing the medial capsule. According to the extent and localization of
the contracture the origin of the lateral and intermediate vastus of the quadriceps muscle should be
severed, or be incised in an inverted V-shape at the muscle-tendon border of the suprapatellar
tendon, and should be reconnected with the knee bent, or the medial capsule narrowed and the
medial vastus fixed on the lateral side of the patella. (Green procedure).
Fixation should be accompanied by early active mobilization, so that active extension may be
complete, and the patella luxation solved as well. The limb should be fixed in a 45o-degree bent
position of the knee in a cast or in a passive motion device for 3-4 weeks. Active physical therapy
aimed for the quadriceps should be continued for a long period of time.
The lateral subluxation occurring at the end point of extension is most similar to habitual patella
luxation. It occurs at every extension, but is accompanied by milder symptoms, so treatment
usually isn’t’ necessary.
VII./3.3.: Recurrent patella luxation and subluxation
The patella may occasionally subluxate or luxate laterally, and may reduce spontaneously.
Swelling and pain may develop acutely. It is three times as common in girls in adolescence as it is
in boys.
Etiopathology
Similar to habitual patella luxation, the dislocation of the patella is usually lateral, and first
presents as a post-traumatic luxation. Patient history reveals trauma, but usually not direct injury
of the patella, but an unfortunate wrong movement while jumping or playing sports. In recurring
cases the patient is already aware of which movement causes the luxation, and takes care to avoid
it. The luxation recurs with various but increasing frequency, once or twice annually, initially, and
may become a daily occurrence eventually.
An important factor of the disease is looseness of the medial capsule and the retinaculum. The
vastus medialis may be weaker, but the later muscles are usually stronger. Certain factors may
cause a disposition for this disease, like a high riding patella, hypoplasty of the lateral femur
condyle or the lateral half of the patella, genu valgum, lateralization of the tibial tuberosity, or
torsion of the leg.
Clinical symptoms
Luxation of the patella does not occur to typical trauma. Due to spontaneous reduction of the
patella sometimes it is hard to determine based on patent history whether luxation occurred or not.
Recurring luxation makes diagnosis easier.
Following the acute injury the knee is swollen, and patient may develop hydrops or hemarthros.
Patients have tenderness on the medial side of the patella, and if we swiftly move the patella
laterally, patient will signal a sudden sharp pain, and may push our hands away. The patella is
usually subluxated laterally.
Figure 2.: If the patellar ligaments are loose and the patella is in a lateral position, it may be subluxated easily.
After a longer period of time patient may develop sing of chondromalatia. We may also observe
the factors leading to predisposition for this disease.
Radiological signs
X-rays are taken with the patient lying in a prone position, and knees bent to a different degree, so
the hypoplasty of the lateral femoral condyle and luxation tendencies of the patella may be
revealed.
Figure 3.: Axial X-rays reveal the extent of patellar lateralization.
The examination may be performed with the quadriceps muscle flexed of loose. CT reveals most
information if it is performed with the knee in a 10o degree flexion position.
Treatment
If patient presents with a luxated patella, reduction is performed following proper anesthesia.
Patients usually arrive after spontaneous or manual reduction of the luxation. Hemarthros should
be drained, and the knee fixed in a plaster cast. Active physical therapy aiming the quadriceps
muscle is recommended afterwards.
Conservative treatment, especially active physical therapy aiming the quadriceps muscle may be
attempted following recurrent luxation. A special orthesis may be prescribed to allow patient to
participate in sporting activities. As age progresses the frequency of dislocation decreases, so
postponing surgery is a valid option. Certain situations however require surgical solution. Surgical
procedure should be fitted for the individual. The steps of the procedure usually involve incising
the taut lateral structures (joint capsule, retinaculum, m. vastus lateralis, iliotibial tract), and if
necessary complementing this procedure with narrowing of the medial capsule and retinaculum.
Reinserting a muscle to the patella from the medial side increases muscle strength pulling the
patella medially (m. vastus medialis, m. gracilis). The patella may be fixed medially by
performing tenodesis (i.e. using the tendon of the semitendinosus muscle). The lateral insertion of
the patellar ligament may be reinserted more medially. Predispositions may also be corrected. i.e.
hypoplastic lateral femur condyle or genu valgum.
VII./3.4.: Luxatio patellae congenita
This may easily be set apart from the previous impairment. It presents at birth, though it may be
difficult to recognize. Ultrasound may reveal the place and position of the cartilaginous patella.
When the ossification center of the patella appears, complete lateral luxation of the patella may be
observed on X-ray images.
Figure 4.: Hypoplastic lateral femur condyle and lateral position of the patella is apparent on X-rays.
The patella is positioned next to the lateral side of the lateral femur condyle, and is not reduced
during motion, and usually cannot be reduced manually either. The patella is hypoplastic, and the
patellar ligament is shortened. Valgus and external rotation occurs in the knee joint.
Congenital patella luxation may present in onychoosteodysplasia. This congenital knee deformity
may present with patellar aplasty or hypoplasty, and hypoplasty of the lateral femur condyle. It
may also be associated with congenital deformities of the elbow. A bony spike, an „iliac horn”
may appear on the dorsolateral aspect of the iliac crest. The most common form of the
accompanying nail -dystrophia is the appearance of longitudinal streaks on the nail of the thumb.
This may rarely present on the other nails as well. The disease shows dominant inheritance.
Surgery is required as soon as possible, even though it is not easy to reduce and retain the patella.
VII./3.5.: Patella hyperpression syndrome
It is a typical consequence of aberrant position of the patella, presenting with symptoms involving
the patellofemoral joint only. It is the most usual cause of knee joint pain in girls. It is a
predisposition for patellar luxation.
Clinical symptoms
Symptoms usually consist of patellofemoral pain, with unrestricted knee motion, and the patella
may be subluxated. Pain is usually provoked by sitting for a longer period of time with bent knees,
or walking down stairs. On physical examination pain may be provoked if the patella is pressed
against the femur when the knee is extended, the quadriceps muscle is loose, and the patient is
asked to tighten the muscle (Zohlen sign). The patella is in a lateralized position, the Q angle is
increased (Figure 5.).
Figure 5.: The Q angle, determined by the spina iliaca anterior superior-patella-tuberositas tibiae is increased, it is 15
degrees.
On axial X-rays the patella is in a lateral position, and the hypoplasty of the lateral femur condyle
may be apparent. MRI may reveal secondary cartilage degeneration..
Figure 6.: The patella is in a lateral position, and the
lateral femur condyle is hypoplastic.
Figure 7.: MRI reveals that the patella is in a lateral position,
and we may also see the beginnings of patello-femoral
chondropathy, and consequential fluid build-up in the joint.
Treatment is mainly conservative, chondroprotective medication should be given, and the
strength of the quadriceps muscle increased through physical therapy- Surgical procedures, such
as incising the lateral retinaculum, or medalization of the tibial tuberosity should only be
considered in symptoms persist.