chapter 7: nonarthritic anterior knee pain
Patellar Tendinitis (Jumper's Knee)
Some patients with anterior knee pain have distinct tenderness in the patellar tendon, particularly where it originates on the patella. This is particularly true in jumping athletes (basketball and tennis players seem to develop this problem more frequently than other athletes).
Patellar tendinitis may be very difficult to treat, and the usual nonoperative treatment program may fail to bring improvement, even after several months. Hydrocortisone iontophoresis may be helpful, and alteration of the exercise program may eventually bring relief. A complete program of prone quadriceps stretching and eccentric quadriceps strengthening will help most patients, and a very localized injection of a small amount of corticosteroid will help some patients. The rare patient may require surgical exploration of the tendon, and a small amount of the painful tissue may be excised (Fig. 7.6).
It is important to recognize patellar tendinitis, because the usual treatment programs for patellofemoral pain are not always helpful, and arthroscopy will add nothing to the treatment of this condition.
PREPATELLAR BURSITIS (FIG. 7.7)
The symptoms may be very similar, but the patient generally has a history of prolonged kneeling, and there is not infrequently thickening of the skin over the patellar surface. In acute cases, the prepatellar bursa is swollen, boggy, and tender, and diagnosis represents no problem. However, in subacute cases, there may be less evidence in the physical findings, and a high index of suspicion can differentiate this from more serious patellofemoral problems.
There is a small bursa outside the knee, just proximal to the tibial tubercle and behind the patellar tendon, which is occasionally the source of symptoms. These symptoms are remarkably similar to patellofemoral arthralgia. Physical examination, however, will generally reveal the bursa to be the source of symptoms. Palpation with the knee fully extended and the quadriceps relaxed will provoke acute, and sometimes exquisite, tenderness. When the quadriceps is contracted and the patellar tendon is tightened, the bursa is protected from the examining finger, and palpation will not provoke symptoms. Tenderness in this area may also result from fat pad syndrome or retinacular pain in the peripatellar tendon area. Corticosteroid injection into the tender area may be curative.
This bursa lies underneath the combined insertion of the sartorius, gracilis, and semitendinosus tendons into the proximal medial tibial metaphysis. It serves to reduce the friction between these tendons and the tibial metaphysis at the level of the medial collateral ligament insertion into the tibia. Because of its medial location, the symptoms are more likely to be confused with medial compartment problem, including degenerative joint disease and meniscal lesions. Simple palpation will evoke tenderness and lead to the proper diagnosis. Beware of more serious problems, such as giant cell tumor or sarcoma of the proximal tibia. Do not neglect to take a radiograph.
The infrapatellar fat pads may be traumatized either by direct blow or by being caught between the femoral condyles and the tibial plateaus on extension (25). The latter mechanism is more common in genu recurvatum, in which the space for the fat pad is reduced. It is important to palpate the fat pad for tenderness and to compare it to the opposite side for texture. Symptoms arising from the infrapatellar fat pad are generally accompanied by tenderness to direct palpation, and sometimes induration. It is important, however, not to confuse the synovitis that sometimes accompanies more advanced forms of patellofemoral arthralgia with the disease described by Hoffa (26). The fat pads are covered with synovial membrane and, therefore, if involved with a distinct synovitis, may also participate in general sensitivity. Therefore, it is important to rule out a generalized synovitis if attributing a knee complaint to the fat pad syndrome. Stretching the anterior knee with the patient prone may be very helpful in some patients and, at times, injection with corticosteroid or arthroscopic excision of impinging fat pad will be curative.
The effusion accompanying many forms of patellofemoral disease is often minimal and not accompanied by significant synovitis. However, symptoms from a generalized knee synovitis may be similar to those noted by patients with patellofemoral disease. The effect of a prolonged synovial effusion is to create changes in articular cartilage, which makes the cartilage less capable of withstanding the mechanical forces of normal activity, and thus leads to secondary patellofemoral arthrosis in some patients.
Inside Chapter 7: