The knees and hips take a lot of impact on a day to day basis. Take a look at this article by Nelson Marquez, PT, EdD, and come visit San Diego Sports Physical Therapy for your knee and hip pain today!
As a weight-bearing joint, the knee sustains the most overuse injuries, making knee dysfunction the most commonly referred condition to orthopedic physical therapy practices. During the American Physical Therapy Association Annual Conference & Exposition here in June, Christopher Powers, PT, PhD, and Amy Sanderson, PT, OCS, presented biomechanical evidence that supports their assertion that knee injuries are linked to proximal factors that can influence knee loading.
A focus on these factors may hold the key to an effective knee injury rehabilitation program compared to current traditional treatments that do not take into account any proximal muscle weaknesses, they pair said.
Compensation factors
Powers and Sanderson said that hip muscle weakness and impaired trunk proprioception and deficits in trunk control are predictors of knee injuries. They provided a thorough functional biomechanical analysis of the pelvis, hip and knee during walking and running in order to show a link between abnormal hip mechanics and knee injuries.
“The most interesting part of the discussion is the focus on running and its biomechanical demands on the body,” said Shannon Ryals, PTA, academic coordinator for clinical education at Polk State College, Winter Haven, Fla., an attendee at the presentation. “Specifically, the speakers’ analysis of mid-foot strikers versus heel strikers and the shock absorption of each running style provides helpful information that can be used when you work with runners, athletes engaged in sports that require a lot of running, or those who would like to take up running.”
Powers, associate professor at University of Southern California’s Division of Biokinesiology and Physical Therapy, emphasized that during normal gait, there is a pattern of hip flexion, adduction and internal rotation during the loading response phase of walking. However, during higher-demand activities, such as running or jumping, these patterns are increased significantly, causing the knee joint center to move medially relative to the foot, which is in a fixed position on the ground. The inward movement of the knee joint causes the tibia to abduct and the foot to pronate, resulting in what the speakers called dynamic knee valgus.
Excessive knee valgus has been shown to be linked to diminished hip muscle strength, particularly the hip extensors, and overuse of the quadriceps, they said. “These factors contribute to numerous knee injuries, such as anterior cruciate ligament injuries and patellofemoral joint dysfunctions,” Powers said.
Powers pointed out that with a concomitant hip abductor weakness, pelvic stability is compromised. To compensate, patients with hip abductor weakness tend to elevate the contralateral pelvis and lean the trunk towards the stance limb. This tendency is called compensated Trendelenburg gait. It tends to have a negative consequence to the knee, increasing the valgus moment at the joint and tensile strain to the ACL and medial collateral ligament.
The speakers also traced the link between weakness of the gluteus maximus muscle and overuse of the hamstrings and adductor magnus muscles to compensate for the weakness. Biomechanical analysis revealed that such weakness results in increased hip adduction. The speakers also presented an analysis of the overuse of the tensor fascia lata to compensate for the weakness of the gluteus medius, resulting in increased hip internal rotation. Powers mentioned that these combinations of muscle weaknesses and compensations contribute to the medial collapse of the knee during high-demand activities.
Evaluation and treatment implications
The speakers presented evidence that impairments at the hip may adversely affect knee joint mechanics. They proposed that physical therapists conduct dynamic evaluations of patients with various knee conditions, assessing the entire lower chain and paying close attention to both proximal and distal kinetic and kinematic factors that may contribute to patients’ symptoms and dysfunctions. In addition, they proposed that therapists evaluate the conditions under which the symptoms arise. This entails taking into account the influence of speed and fatigue to when symptoms arise or get exaggerated.
As far as clinical implications, two general principles were presented that can be incorporated in the design of a knee injury intervention program: pelvis and trunk stability and dynamic hip joint control.
Powers theorized that improving hip abductor muscle performance will result in optimal alignment of the pelvis during single-limb activities and protect the knee joint from excessive varus moments created by trunk compensations due to hip abductor weakness. He also emphasized that the development of core programs should consider dynamic pelvis stability as an integral aspect of the training protocol. In addition, the gluteus maximus, shown to be well-suited to protect the knee from proximal movement dysfunctions, should also be considered in the training protocol. “Improving its use may serve to unload the knee by decreasing the need for compensatory quadriceps action to absorb impact forces,” Sanderson said.
Ryals said he couldn’t agree more. He said Powers and Sanderson provided newer dimensions on how to assess and manage knee injuries. He said that the general principles that the speakers suggested to incorporate in the treatment of knee injuries is a departure from commonly selected treatments for knee injuries, which consist of heat or cold modalities, vastus medialis oblique retraining and strengthening, as well as knee taping. “It makes knee dysfunction treatments truly evidence-based rather than based on a recipe or a trial-and-error approach and waiting to see what works best,” Ryals said. He also said that he learned that the emphasis on quadriceps strengthening, without addressing hip extensor muscle weakness, may facilitate increased quadriceps overuse that can be detrimental rather than therapeutic for patients with knee problems. •
Nelson Marquez, PT, EdD, is physical therapy editor of Today in PT.
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