Common Musculoskeletal Injuries in Women
Elizabeth A. Arendt, MDTHE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 7 - JULY 96
In Brief: The causes of women's sports injuries are currently a topic of vigorous speculation in sports medicine. Research has yet to clearly link gender to any injury etiology. Meanwhile, physicians are analyzing gender differences to find ways that women can better condition themselves for sports, avoid injuries, and recover quickly from the injuries that do occur. An analysis of the most common problems active women face—anterior cruciate ligament, patellofemoral, shoulder, and foot injuries—suggests effective strategies for diagnosis, treatment, rehabilitation, and prevention.
Most literature supports the belief that injury rates are sport specific rather than gender specific (1,2). For both sexes, contact sports cause more injuries than noncontact sports do, and strains and sprains are the most common injuries in both men and women (3). Nevertheless, anatomic and physiologic differences between men and women may play a role in injury incidence and type.
Interpreting Gender Differences
A woman's lower leg alignment (wider pelvis, increased knee valgus, greater Q angle at the knee) and its relationship to injury are frequently discussed in books and review articles, though few quality studies support a causal relationship between the two.
Another idea, widely espoused but with little quality documentation, is that women have increased ligamentous laxity. At least two studies (4,5), however, show no difference in knee laxity relative to sex or age, as measured by a knee arthrometer. Many authors have tried to relate loose-jointedness to increased injury incidence. Though Nicholas (6) found that football players classified as loose-jointed suffered more knee injuries than tight-jointed players, subsequent analysis by other authors (7-10) found no such relationship between joint instability and injury. Some speculate that the cyclical effects of women's hormones on soft tissues may contribute to joint laxity; however, the relationship (and its possible link to injury) is not well understood and requires further research.
An increasing body of epidemiologic data reveals that the rate of anterior cruciate ligament (ACL) injuries is higher in women, particularly for those in jumping and pivoting sports (11). The etiology is unclear; however, theories include intrinsic factors (ligament size, ligament laxity, intercondylar notch dimensions, limb alignment) and extrinsic factors (level of skill, level of experience, shoe-floor friction, stylistic differences in sport play, muscle strength and coordination).
A prospective study (12) comparing two National Collegiate Athletic Association Division I women's teams found that the risk of noncontact ACL tears could be reduced by modifying play technique for the three most common mechanisms of injury: plant and cut, straight- leg landing, and one-step stop. These maneuvers were replaced with rounding off turns, flexing the knee when landing, and the three-step stop. There was a significant decrease in ACL injuries when these techniques were taught prospectively.
Though poor conditioning has not been related to an increased incidence of ACL injuries per se, poor conditioning has been related to increased injuries in general. For most women, the baseline level of conditioning is significantly less than that of men (13-17). Studies (18,19) at the US Naval Academy revealed that overuse injuries were more frequent in women; however, as the women became accustomed to the rigors of training, the injury rates for men and women became more similar.
The concept of a "cruciate dependent" knee (20) has been advanced as a reason for increased ACL injuries. This implies that a knee has increased anterior motion, but no pathologic rotation (the pivot shift). Knee hyperextension is typically present. In a cruciate-dependent knee, a torn ACL challenges operative and nonoperative treatment. However, whether this type of knee is more prone to injury is open for speculation.
A recent careful study (21) evaluated 60 male athletes, 40 female athletes, and 40 healthy sex-matched controls who underwent evaluations of anterior tibial translation. Patients were also evaluated for lower-extremity muscle strength, endurance, reaction time, and muscle recruitment. Female athletes demonstrated more knee laxity and significantly less muscle strength, and took significantly longer to generate maximum hamstring torque during isokinetic testing. The results imply that female athletes rely initially on the quadriceps and the ACL antagonists in response to anterior tibial translation. Interestingly, all other groups initially relied on their hamstrings for knee stabilization. Larger numbers of men and women across a variety of sports should be tested to confirm this finding and ensure that this it is gender-specific rather than sport-specific.
Though the etiology of ACL injuries is unknown, the general principles of training for any sport apply: sport-specific conditioning to prevent fatigue, and proper training of sport-specific skills such as jumping and blocking. A common-sense approach toward team play is also appropriate, such as playing under the direction of a knowledgeable coach and playing with competitors of comparable skill level.
Reports of gender-specific ACL injuries in women should not change the way women compete or choose their sports. Ideally, the data will stimulate the medical and research community to examine the multiple variables that may contribute to this difference, in the hope of providing a safer athletic experience for all participants.
Treatment for ACL injury should not vary with patient gender. Nonoperative versus operative treatment should be based on an informed discussion with the patient, reviewing age, work, athletic, and lifestyle issues. This discussion, along with specific injury features, should lead to an informed patient-physician decision on the appropriateness of surgery.
Patellofemoral disorders are observed more often in women than men (16,22,23), though prevalence studies are lacking. "Patellofemoral disorders" is a global term for syndromes that arise from the extensor mechanism (quadriceps muscle, patella, patella tendon) and its surrounding soft tissue attachments. It is useful to separate patella instability from patellofemoral pain syndrome, which can present with or without radiographic malalignment.
Patella instability. Patella instability represents a patella that has normal or abnormal alignment in the femoral groove, but is displaced by internal or external forces. Typically, the displacement is traumatic and is associated with acute effusion. A patella dislocation documented without acute swelling raises the examiner's suspicion for chronic laxity: The tissues are so lax that the patella comes in and out of the groove without traumatizing surrounding tissues. This can result from lack of bony restraining forces, as in congenital hypoplasia of the patellofemoral joint; laxity of the surrounding tissues from recurrent trauma; and/or a hyperlaxity syndrome such as Ehlers-Danlos syndrome.
Patella dislocation. An isolated study (24), supported by many physicians' personal impressions, reports that patella dislocations recur more frequently in females. Most studies (25-31) on acute patella dislocations, however, continue to show a male preponderance. It is difficult to interpret these findings because most of the studies that report acute patella 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 did not classify dislocations according to disruption of soft-tissue ligament restraints or the character of the individual's bony anatomy—likely prognostic indicators. Further study is needed to determine if the following anatomic or gender differences contribute to patella dislocations: increased Q angle, hypoplastic vastus medialis obliquus, knee recurvatum, and gender differences in mechanism of injury. It would also be useful to know if the patient's gender influences physicians' treatment decisions.
Patellofemoral pain syndrome. Patellofemoral pain syndrome (PFPS) is pain in the patellofemoral joint without documented instability. 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 patellofemoral joint, causing pain. Malalignment syndromes are typically picked up on axial radiographic views, as is reviewed elsewhere (32-36). Radiographs define the position of the kneecap relative to the trochlear groove as normal, tilted, and/or subluxed. Subluxation in this instance is chronic malalignment of the kneecap out of its central position in the trochlear groove without frank dislocation. Though radiographs are helpful for treating patellofemoral pain, the vast majority of patellofemoral pain syndromes do not fall into a malalignment category, perhaps because the spectrum of malalignment is not clearly defined. Our inability to fully understand and document patellofemoral relationships through an arc of active motion suggests that PFPS without radiographic malalignment may represent subtle malalignment that is not detectable with current imaging techniques. At this time, PFPS without radiographic malalignment is the most widespread and the most difficult form of PFPS to treat.
PFPS is often associatedwith a limb alignment variant termed "miserable malalignment syndrome" (figure 1) (37). Miserable malalignment involves increased anteversion of the femoral head with forward placement of the femoral head in relation to the shaft. The femur internally rotates to maintain satisfactory coverage of the femoral head in the pelvis. Associated limb accommodation can include knock knees, increased external rotation of the tibia, and a pronated flat foot. This limb alignment has also been associated with increased Q angle, patella alta, and generalized ligamentous hyperlaxity. Though it is more common in women, the overall prevalence of miserable malalignment has not been recorded.
Treating patella problems. Rehabilitation, in particular a quadriceps strengthening program, is widely recognized as useful for treating patellofemoral disorders (38,39) and is eloquently reviewed elsewhere (40,41) However, it is worthwhile to review some important concepts.
When planning a rehabilitation program for women, keep in mind that average female athletes may have less sports experience than men and may be less versed in weight training techniques. This might be particularly true for women educated in the pre-Title IX years who have not had the advantage of experience in school sports. Traditionally, female athletes have had less experience in sports and less access to good coaching and athletic trainers and facilities.
Strength training equipment needs to be sized to an individual to be effective and safe. Standard health club equipment typically is sized for the larger body build of men. Keep in mind that the lowest weight on weight training equipment may be too much for an unconditioned woman. An athlete who has little experience with rehabilitation and strength training techniques should be monitored closely during rehabilitation or strength training.
The shoulder joint is a common site of overuse injuries for active people, particularly those involved in overhead sports or work activities. It is thought that female swimmers with their shorter arm length and shorter bodies must take more strokes and, hence, increase the number of shoulder insults relative to the distance covered. Because women have relatively weaker shoulder girdle muscles, they must work harder to cover the same distance or to do the same work. Also, women are rarely encouraged to train or strengthen their upper body musculature, which handicaps them in sport and work activities that involve their upper arms.
Impingement syndrome. The most common shoulder overuse injury is "impingement syndrome," irritation of the rotator cuff muscles and their surrounding soft tissues. The physical exam is characterized by anterior and anterolateral shoulder pain. This pain can be reproduced by the "impingement sign"—forceful forward flexion of the shoulder at 90° with internal rotation of the humerus, which pinches the rotator cuff beneath the bony acromion. Impingement syndrome is characterized by rotator cuff inflammation that reduces the subacromial space and thickening of the bursa sack that rests above the rotator cuff muscles. Repeated impingement creates a vicious cycle of increased edema, decreased subacromial space, and increased inflammation from more pinching or impingement on these tissues.
Increased capsular laxity. Increased capsular laxity, particularly anterior laxity, is another possible cause of shoulder pain. An athlete with mild shoulder laxity may have no problems with everyday activities, but may have discomfort or weakness during repetitive overhead motions, which may present as transient joint subluxation pain or as transient discomfort down the arm. When subluxation presents as pain, it can be confused with the impingement sign because it involves inflammation of the rotator cuff musculature. This kind of impingement syndrome is important to distinguish from impingement syndrome without laxity, particularly when considering surgery. Symptoms are likely to recur if surgical resection of the bursa to increase the subacromial space is performed without recognizing the patient's anterior laxity. Distinguishing impingement and instability pain may be difficult; the apprehension test (figure 2a: not shown) and the relocation test (figure 2b: not shown) may help differentiate the two conditions.
Treating shoulder problems. Treating shoulder problems involves progressive strengthening of the rotator cuff musculature and identifying mechanical errors and fatigue issues related to sport or occupation.
When treating impingement syndrome one must pay particular attention to repetitive issues of training or work. Proper warm-up and pacing activity increases can help prevent impingement syndrome. All shoulder muscles should be strengthened, particularly those of the rotator cuff. All strengthening activities should be done below the level of the horizon, with emphasis on internal and external rotation exercises.
The same caveats regarding the limitations of exercise equipment for women's knee rehabilitation apply for women's shoulder rehabilitation. Additionally, exercise equipment that places the hands in the starting position behind the vertical plane of the ears can force the proximal humerus anteriorly in the glenoid. Weight machines should not be used repetitively by athletes who have shoulder instability, and should be used cautiously by those who have shoulder impingement, unless exercisers take care to avoid subjecting the shoulder to repeated anterior force.
Foot discomfort can hinder activity, and foot problems, particularly bunions and other toe deformities, are more common in women. It is difficult to know if foot problems are hereditary or are secondary to the effects of wearing dress shoes. Frequent wearing of high-heeled shoes can cause relative tightness of the Achilles tendon and lead to forefoot symptoms from increased stress on the metatarsals.
A bunion, an inflammation of the bursa over the medial prominence of the first metatarsal, can develop when pressure on the medial aspect of the metatarsal increases the space between the first and second metatarsals (figure 3). The pressure creates a bend in the toe at the first metatarsal—the typical hallux valgus deformity. As hallux valgus increases, pressure on the second phalanx can cause second-toe deformities, such as hammer toe and/or plantar callosity.
Women's shoes may aggravate bunions and other toe deformities. Frequently, women's shoes are a smaller adaptation of men's shoes, particularly athletic shoes. Women who have a wide forefoot and a narrow hindfoot may have a difficult time finding shoes that fit; often they are forced into a bigger shoe that fits the forefoot but is too big at the heel (table 1). This creates a sloppy shoe that allows the foot to "shuck" back and forth and up and down during activity. The increased motion may aggravate a variety of lesser toe problems, particularly in sports that involve sudden stops and frequent decelerations.
Treatment. Because increased foot pronation can irritate existing bunions, stressing the medial aspect of the first phalanx, medial longitudinal arch supports may relieve pressure on the bunion. Shoe alterations—a wider toe box, a more square toe box, and appropriate protective pads—may also relieve the pressure.
Nonoperative therapy should be explored thoroughly for the active person before surgery is attempted to correct foot problems. Surgery can alter foot mechanics, causing additional problems. Foot cosmesis is rarely a goal for active women.
Prevention. Careful attention to athletic shoe selection will help a woman avoid injury and minimize the forces that can complicate foot problems. A shoe that is built on a woman's shoe last, which has a narrower heel in relation to the forefoot, is tighter at the heel and may provide a better fit. Shoe manufacturers have lasts that differ from those of their competitors; this is why people who like the feel and fit of a certain shoe return to buy the same brand.
The last also helps determine the stability of the shoe. Frequently a foot that needs a lot of stability would function better in a straight-last shoe. Women who need more flexibility in a shoe should select a model that has a curved last.
Motion control versus shock absorption is another important consideration when selecting an athletic shoe. Good athletic shoes have both components, but an emphasis on one or the other may be important for some women. Feet that are generally rigid and high-arched (cavus) will feel better in a shoe designed for maximum shock absorption; feet that are flexible and pronated will benefit from a shoe that provides stability or motion control with a rigid heel counter, a firm midsole, and, often, a straight last.
Focusing on Women
Despite historical struggles, women in the 1990s are participating successfully in sport and exercise. Though musculoskeletal injuries and complaints are maladies of all active people, an understanding of those that occur frequently in women can help physicians make sports and exercise a safe, healthy experience for women and girls.
Dr Arendt is an associate professor and the director of the Sports Medicine Institute in the Department of Orthopaedic Surgery and medical director of men's and women's varsity athletics at the University of Minnesota in Minneapolis. Address correspondence to Elizabeth A. Arendt, MD, University of Minnesota, Dept of Orthopaedic Surgery, 420 Delaware St SE, Box 319, Minneapolis, MN 55455.