Commentary re: “Hip Strength and Knee Pain in High School Runners: A Prospective Study”

Abstract

Patellofemoral (PF) pain is a multifactorial problem; therefore, an increased understanding of the etiology of the condition will improve treatment outcomes and enhance preseason screening for at-risk athletes. The prospective study by Finnoff et al in this issue of the journal will help clinicians identify at-risk individuals and provide some direction for rehabilitation [1]. Increasingly, hip muscle strength, particularly the external rotators and to a lesser extent the abductors, has been identified as being a contributory factor in the development of PF pain because the external hip rotator muscles minimize internal femoral rotation, which will in turn decrease the dynamic valgus vector force at the knee. In a double-blind, randomized, controlled clinical trial, Crossley at al [2] found that the inclusion of anterior hip structure stretching to decrease the adaptive shortening that occurs with femoral anteversion, as well as weight-bearing gluteal training to encourage external rotation of the femur, was extremely effective in reducing the symptoms of PF in a multimodal physical therapy program. Finnoff et al [1] found that it was external rotator, not abductor strength, that was lacking in adolescentdistancerunners.Thisfinding isnotsurprisingbecause the tensor fascia latae,which forms partof the iliotibialband, is anabductorand internal rotatorand isoften tight inpersonswithPFpain, significantly affecting patellar positioning in the trochlea. Although the middle and posterior fibers of thegluteusmediusmusclearepurported tobe theculprit forhipexternal rotatordeficiency, itmaybe the smaller hip muscles—the gemelli and obturator externus and internus—that are responsible for centering the femoral head in the acetabulum, much like the rotator cuff does in the shoulder, and for controllingexcessive internal rotation.As imaging techniquesprogress,ourability toaccessandstudy these muscles will improve. Clinicians also need to be aware that hip strength is affected by the starting position of the hip. Cibulka et al [3] found that hip muscle strength was dependent on the hip position; therefore, if external rotation range exceeded internal rotation range, then the internal rotator muscles were stronger, and this may be the case in the runners who have internally rotated femurs. These authors also used a hand-held dynamometer but ensured reliability by only using one examiner. However, Finnoff et al [1] have quite rightly elucidated inter-rater reliability as an area of weakness in their own study. The reliability of intraand inter-trials of a maximal muscle contraction used for electromyography normalization have been questioned, even in persons without symptoms [4,5], and thus the reliability of a maximal contraction with a hand-held device is even more problematic. The convenience, ease of use, and price will ensure that hand-held devices will stay clinically relevant, but perhaps in the future some external method of attachment rather than relying on an examiner’s counter force will ensure better consistency . Although the number of injured runners in this study was quite small, the authors should be congratulated for a prophylactic study that identifies hip external rotator strength as a factor in the development of PF pain.