1
Background
Patellofemoral pain (PFP) can be defined as retropatellar or peripatellar pain resulting from physical and biochemical changes in the patellofemoral joint. It typically occurs with sport activity and often worsens when descending steps or hills or by prolonged sitting [ ]. This term is used to describe painful symptoms located in the patellar region [ ]. It is a very common complaint in the general population and particularly in young adult and adolescent athletes who participate in jumping and pivoting sports such as basketball, volleyball, and running [ ]. It is reported that almost 25%–30% of all knee injuries seen in sports medicine and up to 40% of clinical visits in the general population for knee problems are related to PFP [ ]. This syndrome is more frequent in female athletes and symptoms may cause sports cessation [ ]. It has been reported to result in limitation of sport and physical activities in 74% of patients [ ].
The physical examination has a key role in PFP diagnosis. It allows to investigate common risk factors such as patellar malalignment, muscular retractions, hip muscle weakness, poor core muscle endurance, and excessive foot pronation.
Imaging is not essential for the diagnosis of this condition and it is only needed in special cases.
Many possible interventions are recommended for PFP management. Due to the multifactorial nature of this syndrome, the clinical approach should be personalized.
In most cases, activity modification and rehabilitation are sufficient to limit the progression of symptoms. Therefore, they should be considered prior to surgical interventions.
2
Synonyms
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Anterior knee pain
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Anterior knee syndrome
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Patellofemoral pain syndrome
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Patellofemoral arthralgia
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Chondromalacia patellae
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Lateral patellar compression syndrome
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Patellalgia
A recent consensus statement from the Fourth International Patellofemoral Pain Research Retreat recommended PFP as the preferred term [ ].
3
Clinical Study
3.1
Symptoms
History in athletes presenting with PFP may reveal recent modifications in sport activities including changes in the frequency, duration, and intensity of training [ ]. The training program should also be evaluated for errors including a rapid increase in exercise intensity, inadequate recovery time, and extreme uphill or downhill running [ ]. A history of similar symptoms indicate that the condition is chronic and is presenting as an acute exacerbation [ ]. The use of inappropriate or excessively worn footwear, recent heavy resistance training and running on altered surface or hills should also be considered.
A history of knee traumatic injuries, including patellar subluxation or dislocation, or surgeries should be noted, as they may directly damage the articular cartilage or change the forces across the patellofemoral joint, resulting in PFP [ ].
Patients with PFP typically describe vague pain behind, underneath, or around the patella. This pain usually appears with activities such as squatting, running, and use of stairs [ ]. If asked to point to the site of pain, patients may place their hands over the anterior aspect of the knee or draw a circle with their fingers around the patella. This sign is known as the circle sign and is suggestive of PFP.
The onset of symptoms is usually gradual. The pain may be unilateral or bilateral and is usually described as dull, but may be sharp [ ]. Sometimes, patients report stiffness or pain on prolonged sitting with the knees flexed. This is known as the theater sign [ ].
Patients may occasionally report knee instability concomitant to the pain occurrence due to quadriceps muscle inhibition, or locking while going from knee extension to flexion, and a feeling of a popping or grinding can be present [ ].
3.2
Physical Examination
A physical examination is the key to PFP diagnosis, but there is no single conclusive clinical test [ ]. A variety of tests have been advanced to diagnose this condition.
3.2.1
Vastus medialis coordination test
The patient lies supine, the examiner places his fist under the subject’s knee and asks the patient to extend the knee slowly. The patient is instructed to achieve full extension. The test is considered positive when a lack of coordinated full extension is apparent, that is, when the patient either has difficulty to smoothly achieve extension or uses the extensors or flexors of the hip to accomplish extension. A positive test may be an indicator of dysfunction of the vastus medialis obliquus muscle [ ] ( Fig. 1.1 ).
3.2.2
Patellar apprehension test or smillie test
The patellar apprehension test is performed with the patient in supine position. The examiner uses one hand to push the patient’s patella as lateral as possible. Starting with the knee flexed at 30 degrees, the examiner grasps the leg at the ankle with the other hand and performs a slow flexion of the knee and hip. The lateral patellar slide is maintained throughout the test. A positive test consists of orally expressed apprehension or an apprehensive quadriceps recruitment [ ] ( Fig. 1.2 ).
3.2.3
Eccentric step test
This test requires the use of a step that is 15 cm high or more accurately with a height equal to 50% of the length of the patient’s tibia. The patient is asked to stand on the step, put the hands on the chest, and step down as slowly and smoothly as possible. The patients should keep the hands on the chest throughout the test performance. The eccentric step test is considered positive when the patient reports knee pain during the test performance [ ].
3.2.4
Waldron’s test (Phases I and II)
To do Phase I of Waldron’s test, the patient lies supine and the examiner presses the patella against the femur while performing a passive knee flexion with the other hand. For Phase II, the standing patient performs a slow, full squat, again with the examiner performing a gentle compression of the patella against the femur. In both phases, crepitus and pain are considered signs of PFP disorders [ ].
3.2.5
Clarke’s test or patellofemoral grinding test or Zohlen’s test
The grinding test is performed with the patient lying supine. The examiner presses the patella distally (with the hand on the superior border of the patella) and then requests the patient to contract the quadriceps muscle. The test will be considered positive if the patient’s pain is reproduced [ ] ( Fig. 1.3 ).
3.2.6
Standard step-down test
Standard step-down test is very similar to eccentric step test, except that the patient should stand with arms on the hips and be instructed to squat down 5–10 times consecutively in a slow and controlled manner until the heel touches the floor, maintaining his balance at a rate of approximately one squat per 2 s. Scoring of the deviations in the trunk, pelvis, hip, and knee reveals the onset timing of the anterior gluteus medius, hip abduction torque, and decreased lateral trunk strength [ ].
Excellent interrater and intrarater reliability has been reported for this test [ ].
In addition to these tests, the clinical evaluation should include hip muscle strength evaluation looking for a misbalance between hip internal rotators/external rotators and hip abductors/adductors and podoscopic examination of the feet looking for over pronation since these abnormalities have been described as risk factors for PFP [ ] ( Fig. 1.4 ).
