Concepts For Assessment Of Anterior Knee Pain In Relation To Muscle Function

Abstract

PURPOSE: Anterior knee pain in the young adult is associated with patello femoral rather than femoral tibial dysfunction (Kristin M Houghton 2007). The relationship between vastus medialis oblique strength and anterior pain and disability has been suggested (S. O'Reilly 1998). The lack of consistent methodology in objective measurement of the quadriceps muscles have made evaluation of the link between pain and altered muscle function difficult to assess. Using a novel methodology we demonstrate a biomechanical protocol to access the deficiency of the quadriceps muscles in patients with anterior medial knee pain. METHODS: A biomechanical evaluation was conducted on 54 patients with anterior medial knee pain (34 females and 20 males). All patient x-rays were normal (alignment and joint space between the femur and the tibia as well as between the femur and the patella) through interpretation by a blinded radiologist. A Kistler force plate, a VICON motion analysis system and surface electromyography were used to quantify biomechanical function during isometric, walking and squatting exercises. RESULTS: For 42 of the 54 (78%) subjects, during isometric and walking exercises we observed that activation of the VMO, rectus femoris (RF) and vastus lateralis (VL) muscles of the symptomatic leg was not significantly different from those of the asymptomatic leg (p<0.01). However, for 31 patients (57%) during the eccentric phase of the squat exercises, the symptomatic leg presented with high activation of VL compared to VMO and RF (p<0.01). During the concentric phase, 45 patients (83%) presented with higher activation of the VL compared to the VMO. CONCLUSION: VMO activity during squatting for the symptomatic (patient with anterior medial knee pain) leg differs fundamentally during walking and isometric exercise compared to squatting tasks. Moreover, the relative contribution of the VL compared to the VMO during the eccentric phase of the squat exercises was different to those recorded during the concentric phase. Therefore, we suggest that maximal isometric and or isokinetic exercises are not sufficient to access the quadriceps function in relation to anterior knee pain. A thorough biomechanical assessment, including functional testing to reproduce the patient's pain and locate the nature of the symptoms is suggested.