Sunday, March 6, 2011

Patellofemoral syndrome

Synonyms : Anterior knee pain, Chondromalacia patellae, Patellofemoral arthralgia, Patellar pain,  Maltracking, Patellalgia.


Patellofemoral Syndrome, is the most common ailment involving the knee in both athletic and nonathletic population. In sports medicine clinics, 25% of patients complaining of knee pain are diagnosed with this syndrome, and it affects women twice as often as men. Despite the common occurance of this disorder, there is no clear evidence of the definition, etiology, and pathophysiology. The most common theory is that the syndrome is an overuse injury from repetitive overload at the patellofemoral joint. This increased  stress results in[hysical and biomechanical changes of the patellofemoral joint. The literature has focused on identification of  risk factors leading to altered biomechanics to produce maltracking of the patella in the femoral trochlear groove and thus stress at the patellofemoral joint. Possible pain generators include the subchondrial bone, retinacular, capsule, and synovial membrane. Historically, the histologic diagnosis of chondromalacia had been associated with patellofemoral syndrome. However, chcondromalacia is poorly associated with the incidence of patellofemoral syndrome.

Forces acting on knee

Isolating the knee joint as it is possible to see in the figure can show that the forces that acting on patellofemoral joint (PFJ) on extension of the knee are the quadriceps muscular force (FQ), the force is transmitted to the patellar tendon (FPT) and the reaction force generated on the PFJ (FPFJR). So the FPFJR increases proportionally with the knee flexion, not only increases with knee flexion due to the resultant force rise but also because of the flexor lever arm, which requires a quadriceps response, increases in length.
As a general rule it is not advisable to bend the knees excessively, when they are under strain. Additionally it seems now very logic that losing weight obese patients can improve their conditions since the FPFJR is decreased, since it has less weight to support.


The patient with patellofemoral syndrome will complain of diffuse, vague ache of insidious onset. The anterior knee is the most common location for pain, but some patients describe posterior knee discomfort in the popliteal fossa. The discomfort is aggravated by prolonged sitting with knees flexed, as well as on ascending or descending of stairs and squating because this positions place the greates force on the patellofemoral joint. The patient may also experience pseudolocking when the knee momentariy locks in an extended position.


The examination focuses on identification of risk factors that contribute to malalignment and rules out other pathologic processes associated with anterior knee pain. Tenderness to palpation at the medial and lateral borders of the patella may be beneficial. A minimal effusion may also be present. The results of manual testing for intrarticular disease, such as the Lachman (Anterior cruciate ligament) and McMurray (menisci) maneuvers, will be negative.
The presence of femoral anteversion, tibial internal rotation, excessive pronationat the foot, increased Q angle, and inflexibility of the hip flexors, quadriceps, iliotibial band, and gastrocnemius-soleus should be determined.
The patella position ( baja or alta, squinting or grasshopper) should also be assessed with patient sitting and standing. Each of these factors has either a direct or an indirect influence on the tracking of the patella with the femur.

The Q angle is the intersection of a line from the anterior superior iliac spine to the patella with a line from the tibial tubercle to the patella. This angle is typically less than 15 degrees in men and less than 20 degrees in women. An increased Q angle is associated with increased femoral anteversion and thus patellofemoral joint torsion. However a consensus on the importance of an increased Q angle is lacking. Tight hip flexors quadriceps, hamstrings and gastrocnemius-soleus will increase knee flexion and thus patellofemoral joint reaction force. A tight iliotibial band will increase the lateral pull of the patella through the lateral retinacular fibers. It is necessary to assess each of these components in the lower extremity kinetic chain to prescribe a specific physical  therapy  program for each individual.


The patient with patellofemoral syndrome will avoid activities that provoke the dicomfort initially, such as stair climbing. Prolonged sitting in a car may be difficult. In chronic, progressive cases, ambulation may be enough to incite the pain, making all activities of daily living difficult.


Patellofemoral syndrome is a clinical diagnosis. Plain films may be used to evaluate Q angle and patella alta or baja. Advanced imaging such as MRI is reserved for persistent cases that do not respond to conservative care to rule out intra-articular disease. Bone scintigrams revealed diffuse uptake in the patellofemoral joint in 50% of patients diagnosed with patellofemoral syndrome.

As in other overuse injuries, the initial treatment focuses on decreasing pain. Icing is beneficial, particularly after activities. NSAIDS may be used in a judicious manner. Relative rest with non-weight bearing activities may also be beneficial. A neoprene knee sleeve with patella cutout is helpfull to increase proprioceptive feedback. McConnel's taping method can be used during the acute phase to reduce pain and to increase tolerance of the therapeutic exercise program.
Patella bracing was shown to reduce pain and to improve  function in patients with patellofemoral syndrome but no more succesfully than therapeutic exercise.

With no consensus on the etiology ad pathophysiology of patellofemoral syndrome, numerous treatment protocols and therapies have been used in the literature. Nevertheless most patients respond to a directed rehabilitation approach with therapeutic exercise. The RHB program should address deficiencies in strength, flexibility, and proprioception. Strength training can be achieved with both open and closed kinetic chain exercises. Open kinetic chain exercises occur when the distal link, the foot, is allowed to move freely in space, During closed kinetic chain exercises, the foot remains in contact with the ground, resulting in a multiarticular closed chain kinetic exercise.
An example of an open kinetic chain exercise is a leg press extension. A closed kinetic chain exercise is also less stressful than open chain exercises at the patellofemoral joint in the functional range of 0 to 45 degrees of knee flexion.

These exercises can be performed in multiple planes in a ''functional'' rehabilitation program as the picture next to the text shows.
This may entail having tha patient perform a lunge (A) in the coronal, saggital and transvers planes, simulating positions applied during daily activities. These exercises can also stress the patient's balance by performance of the lunges with eyes closed. Through this functional or skill training, the patient is being prepared for all functional tasks by achieving efficient nerve muscle interactions.

Many studies have focused on selective strengthening  of the vastus medialis obliquus as a dynamic medial stabilizer on the patella. Selective VMO strengthening may be achieved with combined hip adductions because the fibers of the VMO originate on the adductor magnus tendon and to a lesser extent , the adductor longus. However, attemts at proving isolated recruitment of the VMO in relation to the vastus lateralis have failed. Nevertheless, quadriceps strengthening in general should be incorporated in the rehabilitation program through closed kinetic chain and functional exercises.

Injection are not indicated because this is primarily a maltracking phenomenon without a clear consesus on the pain generator.
Surgery is rarely indicated, and directed rehabilitation program is often successful. However, several techniques have been illustrated in the literature. These include lateral retinacular release to decrease the latera force, proximal and distal realignment procedures, and elevation of the tibial tubercle.


Persistent chronic cases of anterior knee pain may show progressive degenerative changes at the patellofemoral joint, such as severe (grade IV) chondromalacia patellae.


Over compensation for the malaligment may occur with surgical techniques such as the laterar retinacular release. The surgeon may lyse too many fibers, leading to increased medial tracking. Many of the realignment procedures should also be reserved for the skeletally mature patient.

Frontera R.Walter, Silver K.Julie,Rizzo D. Thomas, Essentials of Physical Medicine and Rehabilitation Musculoskeletal Disorders, Pain, and Rehabilitation  2nd edition 2008 Saunders Elsevier, ISBN:9781416040071

Kapandji I.A, Churchill Livingstone. The physiology of joints vol.2 Lower Limb. Paris: Librairie, Maloine,Paris, 1987.0443036187

Braddom L.Randall, Physical medicine & Rehabilitation fourth edition,2011, Saunders, Elsevier, ISBN:9781437708844


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