Authors: David Guerrero Ramos, Salvador Pitarch Corresa, María José Vivas Broseta, Marina Vidal Pedros, Ignacio Bermejo Bosch.
Instituto de Biomecánica de Valencia
Universitat Politècnica de València
Edificio 9C. Camino de Vera s/n
(46022) Valencia. Spain
Patellofemoral pain syndrome is one of the most frequent causes of knee pain. Biomechanical analysis provides the key information that is required to prescribe therapeutic exercise because current tests, whether diagnostic or functional, do not provide sufficiently specific and reliable information. In comparison to standard technologies, which tend to be complex and tedious, the Kinemov/IBV software facilitates a biomechanical analysis in a streamlined, fast and objective way. This biomechanical analysis makes it possible to identify the deficits of each joint and to create a customized therapeutic exercise program.
INTRODUCTION
Of all the causes of knee pain that healthcare professionals encounter in their daily practice, patellofemoral pain syndrome is one of the most common. Although it can affect people of all ages and levels of physical activity - so much so that it can be found in 20-25% of the active population - it is more prevalent among women, adolescents and amateur runners.
Its origin is complex and depends on multiple factors. The most common hypothesis to explain the onset of this problem is that it is biomechanical in origin. Some of the causes that have been identified are an increased load on the patellofemoral joint, a patellar tracking disorder, altered joint kinetics and kinematics or muscle imbalances, contributing to increased stress on the joint and causing pain behind or around the kneecap.
There is evidence to show that patellofemoral pain syndrome impairs the patient’s functional ability. Previous studies show decreased ankle dorsiflexion and increased pronation as pain increases when patients support their own body weight during such exercises (1). With respect to the knee, reduced knee flexion can be observed when the patient performs unilateral functional movements (2, 3) while a greater external rotation of the knee can be observed in runners suffering from this symptomatology compared to healthy runners (4).
This is why, in order to diagnose, rehabilitate or propose any type of intervention related to this pathology, it is important to have an initial biomechanical assessment. This makes it possible to identify kinetic and kinematic variables of the different joint segments that may be affected. In this way, we will obtain quantifiable data that will allow us to assess the functional capacity and the deficits associated with the patients’ ailments.
Currently, doctors and researchers are concerned about the associated factors in people with this pathology in relation to diagnosis and the reliability of measurements obtained in functional tests that can detect kinematic and kinetic differences (5). Moreover, physical examination and medical imaging do not provide sufficient information for decision-making in cases involving patients with this syndrome.
In view of this situation, the aim of this study is to identify the biomechanical differences between the affected side and the healthy side of a patient suffering from patellofemoral pain in order to focus the therapeutic exercise on the subject’s deficits.
MATERIAL AND METHODS
A case report
A twenty-eight-year-old male reported unilateral pain in the anterior area of his right knee when carrying out forceful knee flexion movements. His point of maximum pain occurs when going up and down stairs. Two functional tests were carried out in the Human Movement Laboratory at the Instituto de Biomecánica (IBV), using biomechanical variables to quantify the pain that he was experiencing in his affected leg with respect to his healthy leg. These variables will help both his physiotherapist and his physical trainer to obtain key information in order to devise an individualized therapeutic exercise program.
Test method
Assessment protocol
Clinical assessments in patellofemoral pain syndrome include functional movements to identify the location of the pain and activities that increase its symptoms. Two functional tests have been chosen: Single Squat Leg (SLS) and Forward Step Down (FSD), to increase the load on the knee unilaterally, in accordance with the pain symptoms reported by the patient. The assessment was performed by a physiotherapist, and it took 30 minutes to complete the protocol.
The SLS test consisted of two repetitions of a unilateral squat with each leg, performing the movement at the maximum range that the patient could manage without taking his heel off the ground.
The FSD test consisted of stepping down a step from a height of twenty centimeters. The initial position was a unipodal support with the hands on the hips. After being told to do so, the patient took a step forward and immediately returned to the initial position. This was repeated three times, always in a unilateral position.
Technology for biomechanical analysis
To make the recording, we used the Kinemov/IBV application (Figure 1), a motion analysis system offering a choice of myriad biomechanical models. It interfaces with force platforms, an electromyography system, inertial sensors and photogrammetry systems.
As can be seen in the results section, the system makes it possible to choose multiple study variables and combine them into different types of graphs and tables to facilitate the analysis and interpretation of the biomechanical assessment tests.
For this study, a predefined bilateral lower limb model with seventeen markers was used to compare the affected limb against the healthy one.
Figure 1: Example of results rendered by the Kinemov/IBV software.
RESULTS AND DISCUSSION
During the SLS test, it can be seen that the patient’s affected leg has a reduced range of flexion and greater external rotation at the knee (Figure 2). Less dorsiflexion of the ankle and greater eversion of the foot can be observed, while the healthy leg has greater dorsiflexion, and the foot is in inversion. It can also be seen that, when the subject exerts greater effort during the second repetition, there is a tendency towards greater external rotation of the affected knee (Figure 2) and excessive eversion of the foot (Figure 2).
Figure 2: Graphical representation of joint range versus time when performing two repetitions of the Single Leg Squat.
With regard to the FSD test, the patient presents the same alterations as he did when performing the SLS. The results show an evident difference between the healthy and the affected limb, resulting in greater knee flexion in the healthy leg, and greater external rotation in the affected leg (Figure 3).
As for his ankle, he has a reduced range of dorsiflexion in the affected leg, and excessive eversion when stepping down. Furthermore, his healthy foot tends to be in inversion, and the affected foot in eversion, resulting in a much higher rate of pronation in the affected leg (Figure 3).
Figure 3: Graphical representation of joint range versus time when performing two repetitions of the Forward Step
As we observed with the Kinemov/IBV software and the functional tests carried out, biomechanical alterations are detected in the leg affected by this pathology with respect to the healthy leg. A lower flexion range is obtained in the knee, as was the case in the studies performed by Seeley et al. (2021) and Dos Reis et al. (2015), and less dorsiflexion in the affected ankle, as shown in the study by Tan et al. (2020). We also obtain greater external rotation of the knee, as in the results of Wirtz et al. (2012), and greater ankle eversion when the subject performs unilateral movements, as in the study by Tan et al. (2020). These biomechanical alterations may be responsible for the patient's knee pain.
These variables provided the professionals involved in the subject's functional recovery with valuable information. The goal of any therapeutic exercise program is to help the tendon to build up tolerance to load without causing further damage to the structure of that same tendon.
This helped the professionals to refocus and customize their treatment. They knew that, as the patient was in pain, the first thing they had to do was to control his load management and modulate the pain. They therefore followed the recommendations of current scientific evidence and set about planning isometric and eccentric quadriceps exercises to increase the strength and flexibility of his knee joint.
Based on the data obtained from the Kinemov/IBV, they refocused their short-term protocol in two specific ways. Their first goal shifted radically towards correcting the potentially harmful weight-bearing pattern of the affected leg by correcting the dynamic knee valgus. They refocused the treatment on strengthening the gluteus medius and developed a specific proprioceptive program for the knee and ankle. The second goal was to balance the range of motion with respect to the healthy leg in the sagittal plane. To achieve this, exercises that they had previously intended to use as primary exercises were used as supplementary exercises, depending on the patient’s tolerance and pain.
CONCLUSIONS
After we completed this clinical case, we observed that:
- The biomechanical alterations found in this patient have proven to be very useful when it comes to customizing a rehabilitation program based on therapeutic exercise.
- The Kinemov/IBV computer application is a valuable tool for making better decisions in the clinical setting.
REFERENCES
*Patellofemoral pain syndrome is pain in the front of the knee.
- Tan, J. M., Crossley, K. M., Munteanu, S. E., Collins, N. J., Hart, H. F., Donnar, J. W., ... & Menz, H. B. (2020). Associations of Foot and Ankle Characteristics with Knee Symptoms and Function in Individuals with Patellofemoral Osteoarthritis. Journal of Foot and Ankle Research, 13(1), 1-10.
- Seeley, M. K., Denning, W. M., Park, J., Croft, K., Horton, W. Z., & Hopkins, J. T. (2021). Anterior Knee Pain Independently Alters Landing and Jumping Biomechanics. Clinical Biomechanics, 89, 105458.
- Dos Reis, A. C., Correa, J. C. F., Bley, A. S., Rabelo, N. D. D. A., Fukuda, T. Y., & Lucareli, P. R. G. (2015). Kinematic and Kinetic Analysis of the Single-Leg Triple Hop Test in Women with and without Patellofemoral Pain. Journal of Orthopaedic & Sports Physical Therapy, 45(10), 799-807.
- Wirtz, A. D., Willson, J. D., Kernozek, T. W., & Hong, D. A. (2012). Patellofemoral Joint Stress during Running in Females with and without Patellofemoral Pain. The Knee, 19(5), 703-708.
- Leibbrandt D, Louw Q. Assessing Biomechanics and Associated Factors in Individuals with Patellofemoral Pain in a Clinical Setting: A Qualitative Study Based on Interviews with Expert Clinicians. Knee. 2022 Jan;34:178-186. doi: 10.1016/j.knee.2021.11.015. Epub 2021 Dec 18. PMID: 34933238.
