Knee painful arc, imaging by dynamic sonography: A novel technique 1Muhammad Dughbaj, 2Diaa Shehab, 3Salem Alkandari, 4Levent Ozcakar

Abstract

Patellofemoral movement biomechanics is poorly understood and patellofemoral impingement is scarcely described in literature and only by MRI .We describe in this study a novel technique to visualize soft tissue impingement at and above patellofemoral joint using simultaneous goniometry and real time dynamic sonography and to coin the term Knee Painful Arc. Fifteen patients referred to PMR MSK US Unit with anterior knee pain and tenderness over quadriceps tendon underwent simultaneous goniometric measurements of the painful ROM during Keen flexion Extension and real time dynamic US to visualize which soft tissues are impinged at and above the patellofemoral joint (Fig. 1). Dynamic US examination of two patients showed quadriceps fat pads and bursa impingement underneath prominent superior patellar osteophytes (Pincer Type) (Fig. 2a) reproducing pain at the last 30 degrees of extension Seven patients showed quadriceps tendon (QT) impingement over prominent anterior osteophyte arising from femoral condyle (Cam Type) (Fig. 2b) reproducing pain during the range of 60 degree to full flexion and six patients showed mixed impingement of QT, fat pads and bursa between femoral and patellar osteophytes (Mixed Type) (Fig. 2c) with pain free arc between 30 to 80 degree flexion. To our knowledge this is the first study to use dynamic US and goniometry to diagnose and coin the term Knee painful arc, though painful arc of the shoulder is well described in literature, this technique can help understand mechanism and type of soft tissue impingement, modify exercise prescription using pain free arc exercise and improve rehabilitation outcome.