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Links Tuesday, March 13, Injury Series: Uncovering the role of hip strength and mechanics in the cause and treatment of patellofemoral pain syndrome Today we are tackling the most common running injury of all: As is often the case, there is some controversy about the naming.
Historically, it was termed chondromalacia patellae, which is a softening of the cartilage under the kneecap. It turns out that not all cases of PFPS involve softened cartilage, and not all people with softened cartilage have patellofemoral pain!
But over time it tends to get worse, being aggravated even by short, easy runs. The patella itself is a triangular bone attached on one end to the quadriceps muscles via the quadriceps tendon and attached on the other end to the top of the tibia via the patellar tendon.
The patellar tendon is also a common injury location, and patellar tendonitis was covered in an earlier installment in the Injury Series Changes in knee biomechanics after a. The main function of the patella is to give the quadriceps a mechanical advantage in knee extension.
By raising the tendons away from the center of the joint, the knee can generate more power. The drawback of this is that the patella transmits virtually all of the force to the lower leg during knee extension.
As such, it may be inherently prone to overuse. Adopted from Dixit et al. The backside of the patella slides back and forth during knee flexion and extension in a groove in the femur aptly called the patellar surface.
The assumption is that the development of patellofemoral pain syndrome is due to improper tracking of the patella within this groove.
Key Words: gait, hip muscles, anterior knee pain Key Points N After a 3-week hip-abduction strengthening program, patients with patellofemoral pain syndrome increased muscle N N strength and displayed decreases in both pain and stride-to-stride knee-joint variability. No changes were noted in peak knee genu valgum. BASIC RESEARCH Does Total Knee Arthroplasty Change Frontal Plane Knee Biomechanics During Gait? Karl F. Orishimo MS, Ian J. Kremenic MEng, Ajit J. Deshmukh MD, Stephen J. Nicholas MD. Recent Journal of Biomechanics Articles Recently published articles from Journal of Biomechanics. Effects of freeze-thaw on the biomechanical and structural properties of the rat Achilles tendon.
Where this improper tracking comes from is an interesting puzzle, and will be dealt with later. While chondromalacia is not an uncommon finding among patients with knee pain, PFPS alone is not predictive of cartilage softening or damage, nor is the severity of PFPS pain, as first demonstrated in by Lindberg, Lysholm, and Gillquist, 1 and confirmed in a surgical study by Pihlajamaki et al.
Epidemiology and risk factors: Among runners, one recent study found that it accounts for Since women on the whole have relatively wider hips than men, their Q angle is also larger. This model tied inwell with the pronation paradigmsince some studies found Q angles to be related to foot pronation.
However, a well-designed prospective study published in by Witvrouw et al. In any case, we need to turn elsewhere to unravel the causative factors.
For such a common injury, there is an alarming lack of prospective studies on patellofemoral pain syndrome—especially in runners. The above study by Witvrouw et al. The factors that were associated with development of PFPS were poor quad and calf flexibility, poor explosive strength in the legs measured by a vertical jump testabnormal quadriceps firing patterns, and a hypermobile patella.
A meta-analysis of prospective studies on PFPS published this month, albeit in a relatively obscure journal, concluded that weak quadriceps were a risk factor as well, which we'd expect given the reasonable success of treating PFPS with quad strengthening exercises.
Certainly, several of these factors suggest that the development of PFPS is associated with abnormal forces going through the knee joint. Poor explosive muscle strength, for example, would force the knee joint to absorb more of the impact during running, and inflexible or weak quads might increase forces across the knee joint as well.
Abnormal quadriceps firing patterns is a common finding in patients with patellofemoral pain syndrome, and as such, treatments were devised to address this by specifically targeting the muscle that appears to be firing improperly: Turning to retrospective studies for answers Having exhausted the relatively limited pool of prospective studies and having overturned a few theories already, we must turn to retrospective studies for a clearer picture of who gets PFPS and why.
For example, if we evaluated a sample of runners with PFPS, we might find that they limped on the injured side while jogging. But did the limp cause the injury, or more likely did the injury cause the limp?
That being said, there is a wealth of information from retrospective studies. By far the most common finding is hip strength deficiency. Catherine 9 found that recreational runners of both genders who had suffered any injury tended to have weak hip muscles, both comparing their injured leg to their healthy one and relative to healthy control runners.
So, which muscle groups are found to be deficient in athletes with patellofemoral pain syndrome? As it turns out, almost all of them! That is, a runner with PFPS in the right knee will have weaker hip external rotators and abductors on the right side than the left.
To do so requires a 3D kinematics laboratory with either a treadmill or runway to measure gait differences. Everyone agrees that athletes with PFPS demonstrate altered biomechanics compared with healthy controls.These changes contribute to cartilage damage in the knee, and ultimately OA. As the knee sits between the hip and foot, there's often a relationship between your knee pain and the biomechanics .
knee biomechanics one year after total knee arthroplasty. With regards to surgeon-controlled biomechanical factors, surgery may most successfully address frontal plane knee alignment. However, achieving a good outcome in patient-reported knee-related quality of life may be related to dynamic improvements in the sagittal plane.
Changes in Knee Biomechanics After a Hip-Abductor Strengthening Protocol for Runners With Patellofemoral Pain Syndrome It has been hypothesized by many that a primary factor contributing to patellofemoral pain syndrome is muscle weakness in the hip-abductor.
Biomechanical factors play an important role in the health of diarthrodial joints. Altered joint loading — associated to obesity, malalignment, trauma, or joint instability — is a critical risk factor for joint degeneration, whereas exercise and weight loss have generally been shown to promote beneficial effects for osteoarthritic joints.
The peak angle was defined as the largest valgus angle measured after footstrike and generally occurred during the midstance portion of stance. or stride-to-stride knee-joint variability (P 5.
the patient moves the involved leg back to a angle) after the rehabilitation protocol. keeping the knee straight. the patient moves the involved. Changes in walking ability after knee replacement. Int Orthop Effects of toe-in and toe-in with wider step width on level walking knee biomechanics in varus, valgus, and neutral knee alignments, The Knee, , 24, 6, CrossRef;.