ALFREDOSCHIAVONEPANNI, MARIOTARTARONE, ALESSANDROANTONIOPATRICOLA, DANIELESANTAITI
Introduction
Soccer is performed by men and women, adults, and children and at different levels of expertise. It is estimated that almost 25 million people participate annually [1]. Soccer injuries increase in frequency as the age of the partici- pant increases, and several intrinsic and extrinsic factors play a part.
Basically, injuries in the soccer player can occur anywhere in the body like in every sport, but the lower extremities, more specifically the knee and ankle, are the most injured parts [2–4].
Football is a contact sport, and patellofemoral (PF) problems may be related to a trauma or overuse; both are common PF injuries in recreation- al and competitive soccer players. Pivoting actions combined with kicking and contact with other players leave knees extremely vulnerable to acute injuries. Most common traumatic injuries of PF joints are: acute patellar subluxation or dislocation and, rarely, traumatic osteochondral fracture of the patella [5]. Overuse injuries develop when repetitive stress to bone and musculo-tendinous structures damages tissue at a greater rate than that at which the body can repair them. The pathophysiology of these disorders is unclear but may be related to many factors. A combination of extrinsic fac- tors, such as training errors and environmental factors; and intrinsic or anatomical factors, such as inferior limb alignment and ligamentous laxity, predispose athletes to develop overuse injuries [6]. “PF disorders” is a glob- al term for syndromes that arise from the extensor mechanism (quadriceps muscle, patella, patellar tendon) and its surrounding soft tissue attach- ments. As we shall see elsewhere in the text, it is useful to separate patellar instability from PF pain syndrome.
Biomechanics of the Patellofemoral Joint
The articular cartilage of the patella is the thickest in the body, a testament to the high forces imparted on it; it can reach 7 mm in the central portion of the patella. The articular surface of the patella features facets that vary in size, orientation, and magnitude from person to person [7]. PF cartilage is similar to any human articular cartilage to the extent that it can be considered a biphasic material, with a freely flowing fluid phase and a porous-permeable, fibre-reinforced solid phase [8]. However, patellar cartilage is more perme- able and more pliable than other cartilage, even that of its mating surface on the trochlea [9, 10] and insensate [11].
Patella increases the mechanical advantage of extensor muscles by trans- mitting forces across the knee at a greater distance (moment) from axis of rotation [12]; in full flexion, when the patella is entirely in the inter-condylar notch, it increases the lever arm of quadriceps by only 10%. As the knee starts to come into extension, the patella’s contribution increases until 45° of flex- ion, at which the patella lengthens the lever arm by 30%.
Another important biomechanical function is the transmission of tensile forces; in fact, at nearly full bend, tension in the extensor mechanism has risen to nearly 150% of force passing through tibiofemoral joints; this explains the need for the large area of thick articular cartilage on normal the patella and the femoral condyle.
The patella is subjected to complex loading, and the maximum contact area is at 45° when both the central and the medial and lateral facets are in contact with the sulcus. With the knee in extension position, it transmits almost all of force of quadriceps contraction and thus is loaded primarily in tension. With the knee flexion, however, its posterior surface contacts the dis- tal aspect of femur and it is subjected to compressive forces. The PF joint is considered to be one of the highest loaded musculo-skeletal components in the human body [12]. Joint reaction forces that are created within the PF joint in compression and tension with normal activities of daily living are on the order of multiples of body weight [13]. These high loads have been estimated from 3.3 times body weight with activities such as climbing up or down stairs, to 7.6 [14] times body weight with squatting, and up to 20 times or more body weight with jumping activities [15].
During a 90-min game, soccer player is required to perform different explosive burst of activity, including jumping, kicking, tackling, turning, sprinting, and sustaining forceful contractions to maintain balance and con- trol of the ball. Within this explosive activity, the player runs about 10 km in a match. Kicking a ball is associated with a high knee-joint velocity [16] that, combined with repetitive pivoting deceleration can place extreme stress on the PF articular cartilage.
Patellofemoral Injuries
Acute and overuse injuries to the knee are seen as a result of participation in football activity. Patella subluxation, dislocation or tracking abnormalities can occur rarely as a result of mechanical predisposition as well as direct or indirect trauma to the knee. Cumulative microtrauma or overuse can lead to PF disorders.
Patellar instability
Patellar instability represents a patella that has normal or abnormal align- ment in the femoral groove but is displaced by internal or external forces.
This can result from lack of bony restraining forces, as in congenital hypopla- sia of the PF joint; laxity of the surrounding tissues from recurrent trauma;
and/or a hyper-laxity syndrome, such as Ehlers-Danlos syndrome.
Subluxation in this instance is chronic malalignment of the kneecap out of its central position in the trochlear groove without frank dislocation.
Our inability to fully understand and document PF relationships through an arc of active motion suggests that PF pain syndrome (PFPS) without radi- ographic malalignment may represent subtle malalignment that is not detectable with current imaging techniques.
Traumatic Subluxation/Dislocation
A dislocated patella is typically the result of sudden changes in direction while running or jumping. Any force that causes the knee joint to rotate may displace the patella from its natural position. Injuries may also occur from a direct blow to the knee, but in very rare cases, the patella can dislocate after a powerful muscle contraction by the strong pull of the quadriceps muscles. An isolated study [17], supported by many physicians’ personal impressions, reports that patellar dislocations recur more frequently in female athletes, but most studies on acute patellar dislocations, however, continue to show a male preponderance. It is difficult to interpret these findings because most studies that report acute patellar dislocations in men are not prevalence studies and date from a time when men constituted a much larger majority of athletes than they do now. Additionally, the studies do not classify dislocations according to disruption of soft tissue ligament restraints or the character of the individual’s bony anatomy, which are likely prognostic indicators.
Adolescent players have a higher risk of patellar subluxation/dislocation than professional soccer players because of less training and balance muscu- lar control and because of relatively hypotrophy of the quadriceps muscle, the most important active stabiliser of the PF joint. Increased Q angle (an angle
between the longitudinal axis of the femoral and tibial shafts), hypoplastic vastus medialis obliquus (VMO), knee recurvatum, and gender differences are advocated as co-factors of patellar dislocations, but further studies are needed to determine it.
Diagnosis is based on clinical and anamnestic findings. The patella may slip outwards and stay there, in which case the knee will lock and the player will not be able to straighten it. Most of the time, the patella will reduce itself spontaneously but sometimes will require manual reduction. Players who have acute patellar dislocation generally have an episode of instability and localised tenderness along the medial extensor retinaculum or possibly at the adductor tubercle, which is the origin of the medial PF ligament. Also, the patient has localised tenderness along the peripheral edge of the lateral femoral condyle where impaction from the patella occurs with flexion of the knee. An effusion is often present. Radiographs should be obtained since up 20% of patients develop an osteochondral loose body secondary to patella dislocation [18–21].
Patellar Osteochondral Fracture
Osteochondral fractures complicate approximately 5% of all acute patellar dislocations [18]. This fracture will usually occur at the medial side of the patella or, less frequently, on the lateral margin of the lateral femoral condyle [19–21]. Osteochondral fracture of the patella or the femoral condyle may occur as the patella slides tangentially over the surface of the lateral femoral condyle with the knee in the flexed position, as in landing from a jump or piv- oting movement, or it could be secondary to a direct blow trauma to the frontal region of the knee. In both cases, the characteristic anatomo-patho- logical finding is the complete separation of the uncalcified articular carti- lage from the calcified cartilage of the PF joint; in very rare cases, a direct high-energy trauma can cause the complete rupture of the patella, which has to be confirmed by an x-ray examination.
The player suffering of osteochondral fracture complains of pain, effusion with crepitus, and joint-line tenderness. The preoperative magnetic reso- nance (MR) image will show chondral lesions; traditional x-ray exam can, eventually, show bone fragment on the supra-patellar pouch. In this case, arthroscopic treatment is required for removal the loose body and to debride to a stable margin the chondral lesion.
Patellofemoral Pain Syndrome
PFPS is pain in the PF joint with or without documented instability, which seems to be caused by damage to the under-surface of the patella or PF artic- ulating surfaces (chondromalacia) (Fig. 1), modification of homeostasis [22],
or neural [23] or chemical factors [24]. The etiopathogenesis of PFPS is multi- factorial [25, 26]. Causes include overuse and overload, biomechanical prob- lems, and muscular dysfunction. Because bending the knee increases pressure between the patella and its various points of contact with the femur, PFPS is often classified as an overuse injury; however, a more appropriate term may be “overload”, because the syndrome can also affect inactive patients.
Players with PF pain represent an important challenge to the orthopaedic surgeon because no single explanation or therapeutic approach has fully clar- ified this problem yet. Repeated weight-bearing impact may be a contributing factor, particularly in soccer players involved in activities such as running and jumping where as much as seven times one’s body weight may be trans- mitted through the knee. Knee injuries, such as a direct blow to the front of the knee, are significant contributor factors.
No single biomechanical factor has been identified as a primary cause of PF pain although many have been studied: pes planus, pes cavus, Q angle, and muscular causes. Many authors believe that a large Q angle is a predisposing factor for PF pain even if other authors question this concept [27, 28].
Furthermore, normal Q angles vary from 10° to 22°, depending on the study, and measurements of the Q angle in the same patient vary from clinician to clinician and from the supine to the standing position.
Fig. 1.Patellar chondromalacia of a 32-year-old player
Chondromalacia is a degenerative condition of the articular surface of patella. It is not strongly correlated with patellar pain, but pain occurs as the cartilage becomes soft and begins to break down and is no longer able to dis- tribute pressure evenly along the back of the patella. It is probable that the concept [29] of pressure or friction in considerable flexion, such as in squat- ting, and of compression of the patella over the femoral shaft during quadri- ceps contraction, comes closest to explaining the aetiology of chondromala- cia.
In football players, the amount of potential damage imparted to articular cartilage during exercise is related to the magnitude of the shear and com- pressive stresses absorbed by the articular surface [30]. Malalignment of the lower extremity, femoral anteversion, lateral tibial torsion, tibia vara, genu varum or valgum, subtalar varus, and excessive pronation are frequently cited as pre-disposing to knee extensor mechanism overuse injuries. Thus, PFPS can be further classified as with or without malalignment on axial x-ray.
Malalignment is an abnormal relationship between the patella and the trochlear groove that transmits unusual force to the PF joint, causing pain.
This condition is particularly frequent in adolescent players and is often com- bined with muscle hypotrophy and patellar instability. At this time, PFPS without radiographic malalignment is the most widespread and the most dif- ficult form of PFPS to treat.
The complex causes of PF disorders are most effectively identified through a systematic evaluation of the player’s lower-extremity alignment, patellar mobility, muscle flexibility, strength, and an assessment of soft tissue and articular pain. By combining information from such an exam with a care- ful history and appropriate radiographic studies [dynamic computed tomog- raphy (CT) scan, CT measurement of tibial tubercle to trochlea groove (TT- TG), MR imaging] (Figs. 2, 3), the physician can make a specific diagnosis.
Treatment of Patellofemoral disorders
Acute Dislocation
There are still controversies regarding indications and timing for surgical treatment of acute dislocation. In general, after immobilisation in a brace at 30° of knee flexion for at least 2 weeks, a rehabilitation programme for lower- extremity strength and function should be started. Quadriceps strengthening is a universal recommendation for athletes with PF problems. It should ini- tially avoid exercise in the arcs of motion found to be painful during articu- lar compression and should gradually increase.
a b
Fig. 2a, b.CT scan of patellofemoral joint without (a) and with (b) quadriceps contraction is very important to evaluate the degree of patellar instability
Fig. 3.MRI is the most ap- propriate exam to evaluate chondral pathology
The advantages of closed- versus open-chain exercises are still debated [30]. Steinkamp et al. found that closed-chain knee extension (leg press) gen- erated less PF joint reaction than open-chain knee extension from 45° to full extension of the knee [31]. As rehabilitation progresses and pain decreases, the player should also include sport exercise in the programme. In case of recurrent dislocation or severe instability, a surgical procedure to stabilise the patella is required.
Historically, the advancement of the VMO, portion of the quadriceps mus- cle, or proximal and distal re-alignment alone or combined were advocated in order to prevent lateral patellar luxation. A modern approach is to reestablish a medial soft tissue restraint by repairing or re-constructing the medial PF ligament (MPFL). The clinical significance of the MPFL, in fact, has been demonstrated in a variety of recent scientific publications [32–34] where it is believed to be the essential ligament to be restored to a suitable tension or length after acute lateral patella dislocation.
Patellofemoral Pain Syndrome
Non-surgical management continues to be the mainstay of treatment for PFPS. Historically, this has involved strengthening the quadriceps muscle, in particular, the VMO. Currently, a more global approach to optimising func- tion of the lower-extremity kinematic chain is advocated. This can include optimising the strength of the pelvifemoral musculature to help control limb alignment and rotation, balance between quadriceps and hamstring muscle strength, and balance between individual components of the quadriceps mus- cle bellies, in particular, the medial and lateral dynamic stabilisers of the patella.
An alternative approach would be to recognise that femoral rotation needs to be controlled underneath the patella, and this is largely controlled by the pelvifemoral musculature, in particular, the muscles that control hip rotation.
Therefore, an attempt to maximise strength of the pelvifemoral musculature, including hip extensors and hip abductors, is emphasised. In addition, an anteriorly rotated or hemi-rotated pelvis is a common postural habit of many people with PFPS. This can aggravate PF instability by posturing the femur in internal rotation (which is a coupled motion associated with an anteriorly tilted pelvis) and placing the pelvifemoral musculature in a non-optimised biomechanical position.
Knee activity should be reduced, at least relatively, because the theory that PF pain is an overuse and overload syndrome has merit. A relatively inactive patient can benefit from simply strengthening the leg periodically, as needed.
If the patient is a football player who insists on continuing the same rigorous activity, swimming (avoiding breast-stroke style) or another non-impact aer-
obic activity is a reasonable recommendation. Ice is the safest anti-inflamma- tory medication, but its successful use requires discipline. Applying ice for 10–20 min after sport activity is reasonable. Patients with PFPS have not been conclusively shown to benefit from non-steroidal anti-inflammatory drugs (NSAIDs).
The use of knee sleeves and braces in patients with PF pain remains con- troversial, and their use should not be considered a substitute for exercise. PF braces are an inexpensive, subjectively helpful component of PFPS. Their mechanism of action remains unclear, but most appear to improve patellar tracking through a medially directed force [35]. Changes in regional temper- ature, neurosensory feedback, or circulation may also contribute to their effects. Overall, PF braces should be used in conjunction with a comprehen- sive knee rehabilitation programme that includes strengthening, flexibility and technique improvements.
Patella taping, or the McConnell tape technique [36], was originally reported to have a high success rate in reducing PF pain, but subsequent researchers have been unable to reproduce the results of McConnell’s original study [37, 38]. However, it is the opinion of most physiotherapists treating PF pain and instability that patella bracing or taping can be helpful adjuvants to a mainstay of PF rehabilitation.
The objective of surgical treatment is to correct the malalignment, if pres- ent, and to treat the articular cartilage damage. Damaged articular cartilage can be repaired only partially, as normal hyaline articular cartilage cannot be replaced or reconstructed as yet. Arthroscopic débridement and shaving of degenerated cartilage is of unclear benefit while the electrothermal chon- droplasty seems to cause significant thermal damage [39, 40] and an unac- ceptable level of irreversible chondrocyte injury. The microfracture repair technique [41] generates fibrocartilage, and more advanced autologous chon- drocyte implantation has the potential to re-surface defects in the patella with hyaline-like tissue.
Conclusion
Knee pain in contact-sport athletes is perhaps the most common complaint to confront trainers and physicians. Chondral injuries of PF joint are believed to occur through two distinct mechanisms. Most commonly, they arise through abrasive wear, which results in superficial fibrillation and can be asympto- matic until erosion progresses to subchondral bone. The second type occurs because of disruption of the deep cartilage ultrastructure by large-shear forces, and it is often painful and function limiting.
Traumatic PF injuries are rare in soccer practice, and they occur mainly
during tackling and jumping. The incidence is higher in teen players and at the lower senior series because of their lower grade of training. PFPS with or without degenerative changes in PF articular cartilage is a common overload condition both in division and series players. If a cartilage lesion is present, arthroscopic débridement and microfracture technique combined with a spe- cific rehabilitation programme can offer functional and subjective improve- ment in athletes that can functionally meet the demand of the sport, but we must inform athletes that other procedures may be indicated in the future.
Increased training, as muscle strength and co-ordination, causes a reduction in traumatic injuries while overuse injuries remain constant with a progres- sive pattern.
In conclusion, the diagnosis and treatment of PF problems still remain the greatest enigma for the sport medical physician and orthopaedic surgeon.
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