Evaluation of the quadriceps tendon, patellar tendon, and collateral ligaments after total knee arthroplasty: appearances in the early postoperative period.

OBJECTIVE: To evaluate and compare the normal appearance on ultrasound and magnetic resonance imaging (MRI) of the quadriceps tendon, patellar tendon, and collateral ligaments in the early postoperative period following total knee arthroplasty. METHODS: Within a 6-month period, 10 patients with a total knee arthroplasty were referred for imaging. All patients had surgery within 12 weeks, and both MRI and ultrasound were performed on the same day. Two experienced musculoskeletal radiologists, blind to the results of the opposing modality, assessed the integrity of the quadriceps tendon, patellar tendon, and collateral ligaments. RESULTS: Using ultrasound, we identified a focal defect within the medial aspect of the quadriceps tendon in 8 (80%) patients; a similar defect was detected in 5 (50%) patients on MRI. The patellar tendon was thickened in 10 (100%) patients in both modalities. The medial collateral ligament was visualized in 10 (100%) patients with ultrasound and was demonstrated in only 2 (20%) patients with MRI. The lateral collateral ligament was visualized in 7 (70%) and 4 (40%) patients with ultrasound and MRI, respectively. One moderately sized superficial hematoma was demonstrated on ultrasound but was missed on MRI. All abnormalities identified on MRI were also seen with ultrasound. CONCLUSION: A medial defect in the quadriceps tendon and thickened patellar tendon and medial collateral ligament can be considered normal findings. Knowledge of these findings will assist in preventing incorrect diagnosis of a tear. In our cases, ultrasound detected more findings than did MRI.