[Value of ultrasound after endoprosthesis implantation of the knee joint]

Ultrasound is often applied in the course of treatment after knee arthroplasty, although sonographic normal findings have not been described so far. Characterising these and comparing them to clinical disorders was the purpose of this study. Intra- and extra-articular hematoma and the imaging of the traumatised extension apparatus of the knee joint were of special interest.

During 4 weeks all consecutive patients after knee arthroplasty were examined clinically and sonographically. Furthermore, the blood parameters were controlled for signs of inflammation or coagulation disorders. These findings were then re-checked before the end of hospital rehabilitation treatment.

In all of the patients, ultrasound revealed intra-articular fluid at the beginning and at the end of hospital treatment. The fluid area, differing in extension, was markedly reduced or showed less echogenicity concomitant with an organisation. The patellar tendon in all of the patients showed a loss of echogenicity at the site of operative incision, mostly at the patellar insertion, and a thickening extending throughout the middle part of the tendon even at control. Dynamic ultrasound examination displayed one case of a major defect which had to be revised. Blood parameters of inflammation were decreased, coagulation parameters were normal.

After knee arthoplasty, extended intra-articular knee hematomas are not rare, only being resorbed or organised to a small degree during a rehabilitation period of three weeks, therefore not yielding relevant information for the course of treatment.

The patellar ligaments show alterations comparable to acute tendopathy, thus not recommending use of maximal forces or too high stretching of the tendon tissue. Soft tissue defects with the need for interruption of the rehabilitation programme may be detected sonographically. Further studies will be necessary to explore the course of restructuring. Disorders of patellar sliding movement and signs of prosthetic loosening cannot be sufficiently judged at the present time.