Roentgen Diagnosis of Knee-Joint Effusion

Abstract

In the study of the roentgenograms of a large number of patients admitted to the Station Hospital, Miami Beach Training Base (Miami Beach, Florida), for abnormalities of the knee, changes in the soft tissues have been noted which have greatly facilitated the diagnosis of effusion into the knee joint. These findings are reported since the usually accepted roentgen signs of knee-joint effusion, i.e., anterior displacement of the patella and widening of the joint (3) have been found entirely inadequate in the x-ray diagnosis of this condition. In a review of the literature, it was found that Lewis (4) mentions the presence of a pyriform mass in the suprapatellar pouch and bulging of the infrapatellar ligament in knee hydrarthroses, but does not describe these abnormalities in detail. Löhr and Hellpap (6) report a fullness in the recess above the upper portion of the knee cap in the presence of intra-articular effusion. Other references to the findings to be described have not been discovered. A brief description of the pertinent anatomy of the knee with particular reference to its roentgen appearance seems warranted. Figure 1, A, represents a midsagittal section through the knee, drawn from Gray (1) and Spalteholz (8). It will be noted that the cavum articulare lies just behind the infrapatellar fat pad and then proceeds upward behind the patella to connect with the suprapatellar bursa. The synovia forming the base of the suprapatellar bursa lies in a small recess formed by the posterior surface of the upper portion of the patella in front and the femoral condyles behind. For convenience in description, this space will be designated as the patello-condylar recess. The bursa itself is situated just in front of a considerable amount of fatty areolar tissue overlying the lower end of the femur above the condyles. The upper portion of the bursa is covered in front by the tendon of the quadriceps femoris. Inferiorly, just above the superior surface of the patella, in the patello-condylar recess, the base of the bursa is separated from the tendon by a small triangular mass of fatty areolar tissue. Thus, on the lateral roentgenograms an oval area of comparative radiolucency, about 6 to 10 cm. in length, is seen to lie over the anterior surface of the lower end of the femur just behind the density of the quadriceps femoris tendon. This radiolucency extends downward and anteriorly over the dorsal aspect of the condyles, across the upper end of the joint space, and over the superior surface of the patella just behind the insertion of the quadriceps tendon (2).