Regional interdependence is the concept that “seemingly unrelated impairments in remote anatomical regions of the body may contribute to and be associated with a patient’s primary report of symptoms.” The majority of the literature surrounding regional interdependence in the lower extremity has been focused on low back pain, which has been positively correlated to hip osteoarthritis, decreased strength, neuromuscular control, range of motion, and mobility of the lower extremity. Relationships between the foot, ankle, and the low back have also been reported. The examples of regional interdependence are endless, some more obscure than others, but let’s break down a simple one that may not be all that “seemingly unrelated.” This example is one that I see in many, if not all of my elementary school and high school athletes.
Regional Interdependence and Tibiofemoral (Knee) Pain
The knee, for many young athletes, becomes a problem in sports that involve running, jumping, lunging, and lateral change of direction. Trying to think of a sport that doesn’t involve these movements? Keep thinking… Keep thinking… Exactly. The knee often gets a bad reputation and is the source of a lot of unnecessary force during these aforementioned activities, while in reality your hips and feet are most likely significant contributing factors to your knee pain. So how can your foot and hip be contributing to your knee pain?
The Foot’s Role In Knee Pain
Pes planus, or simply put, having flat feet (Figure 1) is a term that describes an observation in static postures. When moving, your foot may fall into pronation. Pronation is actually a normal part of the gait cycle. In fact, foot pronation is necessary to soften the blow and absorb contact from ground reaction forces when walking.
Figure 1. Foot Pronation
“Over/excessive pronation” is the correctly used terminology that describes the medial longitudinal arch (Figure 2) collapsing towards the ground. Now, how does over-pronation tie into the concept of regional interdependence? Simply put…it starts from the ground up. When the foot makes contact with the ground and overly pronates, increased stress is placed on the medial (inside) aspect of the lower extremity. This medial stress travels up the kinetic chain to the next closest joint (the knee) causing a valgus moment as well as medial tibial rotation (Figure 3). In static standing, valgus knee stress is not a huge issue, but place the knee under significant load with activities such as running, jumping, lunging, and lateral change of direction activities and this stress can cause dysfunction leading to muscle strains, ligament sprains, and capsular restrictions. Know someone who has had an ACL/PCL injury? Consider this… The ACL and the PCL twist around one another forming an “X” pattern. Both the ACL and PCL become taught with medial tibial rotation and subsequent lateral (outside) femoral rotation (Figure 3). Continuing on, the femur (leg bone above the knee) becomes adducted and medially rotated placing stress on the acetabular femoral joint leading to more potential muscle strains and hip labrum pathology. This stress finally makes its way to the sacroiliac joint and lumbar spine.
Figure 2. Medial Longitudinal Arch
Figure 3. Kinetic Chain Breakdown
Figure 4. ACL/PCL
The Hip’s Role In Knee Pain
Aside from anatomical variables such as femoral anteversion (twisting in of the thigh bone at the femoral head) and femoral retroversion, (twisting out of the thigh bone at the femoral head) most of the dysfunction that occurs at the hip is muscular when relating the hip to knee pain. The hip abductors (gluteus medius and tensor fascia latae) along with the gluteus maximus and external rotators pull the hip away from the body in an open kinetic chain position (feet off the floor) such as in sitting. However, when in standing, the activation of these muscles pull the knee outward, away from midline and prevent dynamic genu valgus (Figure 5). In single limb stance, the lack of activation of these muscles causes Trendelenburg’s hip drop, which has been associated with Patellofemoral Pain Syndrome. In fact, subjects with Patellofemoral Pain Syndrome (PFPS) also display 18% less hip abduction and 17% less hip external rotation strength. Muscles such as the Vastus Medialis Oblique (VMO) often take blame for being weak, or under activated in patients with PFPS; however, research has denied this muscle’s ability to be isolated with EMG studies. While the VMO anatomically assists in the “tracking” of the patella, a more regional approach involving strengthening the hip musculature may influence knee mechanics to a greater degree. The biceps femoris (hamstring), rectus femoris (quadriceps) and Illiotibial band (abductor) influence the knee in a more direct way by crossing both the hip and knee joint, directly affecting the knee during functional movement patterns. What does this all do to the knee? Besides the rotary forces I explained above, this valgus stress collapses the lateral knee capsule and puts a significant amount of tensile strength on the medial knee joint deeming it susceptible for ligamentous/cartilaginous (MCL, ACL, PCL, meniscus), tendinous (pes anserine) and capsule injury.
Figure 5. Dynamic Genu Valgus
Using regional interdependence, clinicians can effectively evaluate and treat the body as whole rather than specific joints, which may lead to incorrect diagnoses of associated musculoskeletal disorders. Joints above and below your primary impairment may be contributing factors, and if not addressed, could lead to the re-occurrence of chronic injury. Call us at The Spine and Health Center of Montvale at 201-746-6577 for a physical therapy regional interdependence evaluation today!
Sueki et al. A regional interdependence model of musculoskeletal dysfunction: research, mechanisms, and clinical implications. J Man Manip Ther. 2013 May; 21(2): 90–102.
Nakasagawa et al. Trunk, pelvis, hip and knee kinematics, hip strength and gluteal muscle activation during a single-leg squat in males and females with and without patellofemoral pain syndrome. Journal of Sports Physical Therapy. 2012 June; 42(6).