[Objective]　The purpose of this study was to detect the differences in the presence and movement of a knee wobbling phenomenon (KWP) during four squatting and landing tasks in order to establish the optimal screening task for identifying a potential indicator of ACL injury risk.
[Background]　KWP consists of quick and uncontrollable medio-lateral movements(valgus/varus) of the knee,which may indicate an elevated risk for ACL injury.
[Materials &Methods]　Ten female collegiate athletes participated in this study. Slow single leg squat(SSLS) ,single leg standing(SLS), double leg drop landing from a 30-cm box(DLB),and repeated single leg landing after jumping(RSLJ) were analyzed. Relative valgus(frontal) angular velocity divided by flexion(sagittal) angular velocity(F/S ratio) was calculated. An F/S ratio exceeding 100% was defined as “F/S spike” indicating KWP.
[Results]　The number of valgus and varus F/S spikes were significantly different between the four tasks (p＜.001). The median(range) of the initial knee flexion angles during SSLS,SLS,DLB,and RSLJ was 0.1(0-4.3)°,9.1(3.8-14.5)°,25.5(13.6-46.9)°,and 19.6(14.4-34.5)°,respectively(p＜.001). The median for the number of F/S spikes during each task was 4.5(0.3-7.3), 5.9(4.6-7.0), 0, and 0(0-0.5) times,respectively (p＜.001).　　[Conclusion]　SSLS and SLS induced knee wobbling at low knee flexion angles(i.e.＜25°), which facilitated recognition of the characteristics of knee movement at low flexion angles.

膝揺れ現象は、荷重動作中に生じる制御不可能な膝関節の内外側（内外反）方向の運動であり、ACL損傷危険因子の一つとしてスクリーニングに役立つ可能性がある。本研究の目的を、4つの異なる動作間での膝揺れ現象の出現の違いを明らかにすることとした。10人の大学女性アスリートを被験者とし、低速片脚スクワット（SLSS）、片脚立ち（SLS）、30cm台からの両脚落下着地（DLB）、片脚連続ジャンプ着地（RSLJ）を3次元動作解析装置にて分析した。膝関節屈曲角速度に対する膝関節外反角速度の相対値をF/S値として算出した。F/S値の絶対値が100％を超えるとき、“F/Sスパイク”として、膝揺れ現象の存在を示した。本研究の結果、F/Sスパイクの数、動作開始時の膝関節屈曲角度に、動作間で有意な差が認められた。DLB、RSLJと比較して、SLSSは、より浅屈曲位からの動作を再現し、膝揺れ現象を検出することを可能とする。