Ultrasound examination of tibiofibular widening of forceful knee flexion is recommended for patients with proximal tibiofibular joint instability

Abstract

Background

Proximal tibiofibular joint (PTFJ) instability is uncommon, resulting from violent twisting motions of the flexed knee during sport activities. No known image variables functionally relate the degrees of PTFJ instability.

Objective

This study used ultrasound imaging to quantify the discrimination threshold for PTFJ instability and relevant functional significances.

Methods

Twenty patients (mean age: 42.7 (21–59) years) with chronic PTFJ instability participated in this study. Along with the Knee Injury and Osteoarthritis Outcome Score (KOOS),the tibiofibular distances of the affected and unaffected knees were estimated with ultrasonography in the four standardized conditions at 90° of flexion of the hip and knee, including neutrally relaxed position, passive internal rotation, passive external rotation, and forceful flexion of the knee joint.

Results

During forceful knee flexion, the absolute tibiofibular distance in the affected leg (28.1 ± 4.0 mm) was greater than the unaffected leg (25.1 ± 3.7 mm). Relative changes in tibiofibular distance (RTFD) were different for both legs (affected leg:3.9 ± 2.7 mm; unaffected leg:1.0 ± 1.4 mm) (P < 0.001). The area under the receiver operator characteristic curve for the RTFD was a potent predictor of PTFJ instability (84.5%) with specificity of 95% and sensitivity of 65%. Patients with RTFD greater than 2.95 mm exhibited higher scores on the KOOS subscales of pain (P = 0.043) and quality of life (P = 0.009).

Conclusion

Ultrasonic measurement of the tibiofibular distance under forceful knee flexion is clinically valuable for diagnosing PTFJ instability with functional significance.