Anterior knee pain is possibly the most common presenting symptom in clinical sports medicine practise. Two common causes of anterior knee pain in sportspeople are the patellofemoral syndrome and patellar tendinopathy. Patellar tendinopathy was formerly known as patellar tendinitis but this misnomer is progressively falling out of favor (see Chapter 2). Fat pad impingement is an underdiagnosed cause of anterior knee pain that may mimic features of both patellofemoral syndrome and patellar tendinopathy. The anterior knee anatomy is depicted in Figure 24.1.
In this chapter, we first outline a practical approach to assessing the patient with anterior knee pain, particularly with a view to distinguishing the conditions, and we then detail their management. The chapter concludes with an outline of other causes of anterior knee pain. |
| Clinical approach
Distinguishing between patellofemoral syndrome and patellar tendinopathy as a cause of anterior knee pain can be difficult as their clinical features can be similar. Furthermore, the two conditions may both be present. Both conditions may appear simultaneously as a result of the same biomechanical abnormality or because of overuse, or one may occur first and predispose to the other (see below). The causes of anterior knee pain are listed in Table 24.1. |
Fig 23.1 24.1 Anterior aspect of the knee
(a) Surface anatomy
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(b) Anatomy (ADAPTED FROM THE CIBA COLLECTION OF MEDICAL ILLUSTRATIONS, REPRODUCED BY COURTESY OF CIBA-GEIGY LIMITED, BASEL, SWITZERLAND. ALL RIGHTS RESERVED.)
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History
There are a number of important factors to elicit in the history of an athlete with general presentation of ‘anterior knee pain'. These include the specific location of the pain, the nature of aggravating activities, the history of the onset of the pain, and any associated clicking, giving way or swelling.
Although it is difficult for the patient with anterior knee pain to be very specific in pin-pointing the pain, the area of pain often gives an important clue as to which structure is causing pain. For example, medial patellar pain suggests the patellofemoral joint is a likely culprit, pre-dominantly lateral patellofemoral pain indicates excessive lateral pressure syndrome or iliotibial friction syndrome (Chapter 25), and inferior patellar pain indicates patellar tendon or infra-patellar fat pad involvement. |
The two menisci, medial and lateral, are intraarticular and attach to the tibial plateau. For a long time, the menisci were thought to be functionally unimportant and were surgically removed if damaged. However, the menisci have an important role as a buffer absorbing some of the forces placed through the knee joint, thus protecting the otherwise exposed articular surfaces from damage. By increasing the concavity of the tibia, they play a role in stabilizing the knee. In addition, the menisci contribute to joint lubrication and nutrition. As a result, it is important to preserve as much of the menisci as posible after injury.
The type of activity producing pain also aids diagnosis. Consider two contrasting scenarios that both cause tenderness at the identical infrapatellar site. In one case, precipitating activities, such as basketball, volleyball, high, long or triple jumps, involve repetitive eccentric loading of the patellar tendon. This suggests the diagnosis of patellar tendinopathy. On the other hand, if a swimmer presented reporting pain following tumble turning or vigorous kicking in the pool, where there had been no eccentric load on the tendon but a forceful extension of the knee, the practitioner should suspect an irritated fat pad. The mechanism of injury and the aggravating features are critical to accurate diagnosis.
The onset of typical patellofemoral pain is often insidious but it may present after an acute traumatic episode (e.g. falling on the knee). The patient presents with a diffuse ache, which may be exacerbated by either prolonged sitting (‘movie-goer's knee') or activity. Pain during running that gradually worsens is more likely to be of patellofemoral origin, whereas pain that occurs at the start of activity, settles after warm-up and returns after activity or the next morning is more likely to be tendinopathy. Table 24.2 is an aid to clinical differentiation of the patellofemoral syndrome, patellar tendinopathy and fat pad irritation. As these conditions can coexist, accurate diagnosis can be a challenge.
A history of recurrent clicking may suggest patellofemoral syndrome. A feeling that the patella moves laterally at certain times suggests recurrent patellofemoral instability. An imminent feeling of giving way may be associated with patellar subluxation, patellofemoral syndrome or meniscal abnormality, although actual giving way is usually associated with anterior cruciate ligament instability (Chapter 23).
A history of previous knee injury or surgery may be significant, especially if associated with an effusion. As a result of the effusion, there is reflex inhibition of the vastus medialis obliquus muscle. This may predispose to the development of patellofemoral pain as the medial quadriceps may be inhibited before the lateral quadriceps, which has the potential to set up an imbalance of the soft tissue forces and cause lateral tracking of the patella.
Previous treatment and the patient's response to that treatment should be noted. If treatment was unsuccessful, it is essential to determine whether the failure was due to incorrect diagnosis, inappropriate treatment or poor patient compliance.
Knee swelling is rare in anterior knee pain and, as a general rule, it suggests intraarticular abnormality. A small effusion, however, may be present with patellofemoral syndrome. |
