As an integral part of the knee, the patellofemoral joint is one of the most structurally complex articulations with high functional and biomechanical requirements. The biomechanical structure of this joint, along with its soft tissue complex, is able to withstand compression and tension forces (e.g., releasing the tension around the femur, by transmitting these forces to the patellar tendon), playing a major role to the flexion and extension movements of the knee. Thus, the patella acts as a biological lever arm transmitting the force of the quadriceps muscles to centralize the divergent forces. This mechanism improves the knee extension effectiveness by increasing the moment arm of the patellar tendon (Fig. 16.2). Complementarily, patella has an aesthetic function for the human leg and forms a bony shield, protecting the tibiofemoral joint from direct trauma (external impacts and damage) [1, 4–6].
As a moveable osseous part, patella executes characteristic movements along the different anatomical plans of the human body (Fig. 16.3). In the axial plane, patellofemoral joint features medial-lateral translation, also called glide, and rotation, usually known as tilt. In the sagittal plane, rotation assumes the designation of flexion, and it detected a slight anterior-posterior translation. On the other hand, rotation in the coronal plane is commonly defined as spin. The fitting in the trochlear groove (at 20–30° knee flexion) is observed in this plane as well, although it is not described in the literature as a patellofemoral motion pattern. The patellofemoral joint movements depend on many factors such as the trochlear configuration, medial patellofemoral ligament (MPFL) efficiency, vastus medialis obliquus (VMO) strength, and the tibial internal rotation control (during flexion). In fact, well-developed muscles (the quadriceps and particularly the VMO) may aid the patellofemoral control and protect the joint from wear, preventing many causes of patellofemoral pain, specifically the ones related to the high athletic demands like in football [1, 5, 7].
Fig. 16.3
Representation of the most relevant patellofemoral joint motion patterns: (a) medial-lateral translation and patellar tilt, on the axial plane; (b) internal and external rotation (also designated “spin”), on the coronal plane; (c) flexion and extension, on the sagittal plane – adapted from [7]
Due to the large mobility of the patellofemoral joint (6 degrees of freedom), the contact facets of the patella are often subject to high contact loads. These contact stresses within the patellofemoral joint gradually increase with knee flexion (Fig. 16.4). For instance, a simple daily routine exercise of climbing stairs will reflect in a fourfold increase of the body weight on the patella. Along with this line, due to situations of maximum flexion (approximately 120°), where the tension increases up to sixfold the body weight, the patella is more susceptible to fracture. In this sense, the high torsional loads experienced in the football player’s knee during several football maneuvers (such as pivoting or cutting) may predispose them to an early onset of patellofemoral lesions [1, 5, 6, 8].
Fig. 16.4
Color gradient to represent different degrees of stress areas between the contact facets of the patellofemoral joint – adapted from [3]
Fig. 16.6
Measurements in classic patellar instability risk factors: (a) patellar tilt, angle formed by lines joining the major transversal axis of the patella and the posterior femoral condyles [17]; (b) measurement of the true relationship of the tibial tubercle, TT, to the trochlear groove, TG, using the TT-TG distance [18]; (c) lateral radiograph of the knee shows the lines corresponding to patellar height ratio measurement [18]
Fig. 16.7
MR images of the patellofemoral joint stress testing through instrumented assessment: (a) patellar neutral position without loading; (b) patellar lateral translation under loading; (c) patellar external tilt under loading, in axial view
Activities which increase the patellar compression, such as quadriceps contraction, will typically incite pain. In football, pain-inducing activities include running, kicking, landing from a jump, or falling on the knee. Out of the football field, the pain is typically experienced while kneeling, squatting, climbing stairs, or sitting with the knee flexed. Athletes may struggle with episodes of functional instability, described as collapsing or giving away of the knee, although some authors consider this dislocation of the patella as a “going out” movement of the knee. Usually, the patellofemoral symptomatology is triggered by contact forces within the knee joint. In the context of a football game, traumatic chondrosis of patellar or trochlear cartilage, or even patellar fracture, may occur due to direct trauma, as in the case of tumble on the knee. Despite the fact that the high level of training (strength or endurance, typical in elite levels) and competition may contribute to a proper neuromuscular control and muscular strength, it also can lead to a chronic overuse, often causing patellar chondrosis, as well as patellar or quadriceps tendinopathy. In this sense, other common football-related actions, such as running or kicking, may also contribute to the development of an overuse symptomatology. Scientific literature reports that higher knee abduction moments during landing are predisposing risk factors for both patellofemoral pain and anterior cruciate ligament (ACL) injuries and that these significantly greater force loading rates are verified in female football players, when compared to males [9, 10].
16.2 Etiopathogeny
Anatomical and physiological abnormalities of the patellofemoral joint may represent the cause for multiple clinical problems of the knee [1, 11]. Patellofemoral pain (also known as patellofemoral syndrome) and patellofemoral instability are the most common pathologies directly related to this joint. Four major risk factors were defined by Henri Dejour et al., in 1994, in order to characterize instability in patellofemoral problems [12]. The patellofemoral instability can be subdivided into different grades: firstly as potential instability, when it encompasses patellar subluxation; then objective instability, at least one episode of patellar dislocation has occurred; and designation of recurrent instability is applied when the patient has two or more episodes of dislocations, but there is no consensus on the terminology used worldwide [1, 4, 11, 13–20].
These pathologies often result from anatomical and biomechanical factors related to osseous and soft tissue abnormalities. In this line, four osseous abnormalities can be directly linked to the classical risk factors designated by the Lyon School, as described in Table 16.1. Additionally, other factors related to soft tissue deficiencies can lead to instability of the patellofemoral joint, whose correlation and prevalence on patellofemoral problems have been studied: a torn MPFL, once is the most important medial stabilizer of the patella against the lateral translation; a weakened VMO that may result in significant decrease on the dynamic stabilization of the patella; an excessive femoral anteversion, which externally rotates the tibia and results in an increased quadriceps angle; an excessive tibial external rotation, which leads to a more lateralized position of the tibial tubercle, also increasing the quadriceps angle; a longer patellar tendon, increasing patellar height; as well as the patellar shape Wiberg type C – which has the facets more laterally than medially developed (medial hypoplasia), due to increased lateral stress, in association with tilt and trochlear dysplasia, affecting the articular congruency [5, 11–14, 17, 21].
Table 16.1
Lyon School classic risk factors for patellofemoral instability
Risk factor | Description |
|---|---|
Trochlear dysplasia | Classification (Fig. 16.5) (a) Slight trochlear dysplasia with a concave groove – trochlear morphology preserved with a fairly shallow trochlea (b) Flat or convex trochlea (c) Asymmetry of the trochlear facets – lateral facet convex, medial facet hypoplastic (d) Asymmetry of the trochlea facets – vertical joint and cliff pattern |
Tilt >20° | Excessive passive patellar external tilt, usually above 20° (Fig. 16.6 a), due to quadriceps dysplasia |
TT-TG ≥20 mm | Excessive distance between the tibial tubercle (TT) and the trochlear groove (TG), usually above 20 mm (Fig. 16.6 b) |
Patella alta | High ratio of the patellar tendon length (LT) by the patella length (LP): LT/LP > 1.2 (Fig. 16.6 c) |
16.3 Epidemiology
Regarding the epidemiological aspects, patellofemoral problems constitute one of the most common knee complaints and are more frequent among adolescents and young adults – which represent the most active population group representing a significant long-term socioeconomic burden. Usually, patellofemoral complaints are related to anterior knee pain, which make up about 20–40% of the total knee injuries, affecting up to one third of the young population. Women are known to have higher incidence and severity of the patellofemoral problems. In this sense, gender-specific, sociological, anatomical, and physiological factors might be contributing: abused high-heel wear and sitting with adducted legs, increased pelvic width and consequent excessive lateral pressure on the patella, and levels of estrogen. Both the athletic and nonathletic populations are propitious to this kind of pathology, although it is more common in the first one [3, 5, 12, 14, 19, 20].
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
