Musculoskeletal Injuries in the Tennis Player
Marc R. Safran
Tennis is a sport that is enjoyed by tens of millions of people worldwide, with total participation continuing to increase over the past 30 years. It is estimated that in the United States, total tennis participation exceeds 30 million people annually (51). Tennis is a sport for a lifetime, with competitive tournaments available for those as young as 8 years old and those older than 90 years old.
The mechanics of tennis, a predominantly unilateral armdominant sport with repetitive motions, place the body at unique risk for injury.
The exact incidence of injury in tennis has been elusive, because definitions, methodologies, and populations vary widely between individual studies. A number of investigations have reported tennis injury incidence to be anywhere from 2 to 20 injuries per 1,000 hours of tennis played (4,19,48).
In a comprehensive review of 28 epidemiologic studies on tennis injury that have been published since 1966, Pluim et al. (42) reported the incidence as ranging from 0.04 to 21.5 injuries per 1,000 hours played (42).
This same investigation found that most injuries occurred in the lower extremity (31%-67%), followed by the upper extremity (20%-49%), and lastly the trunk (3%-21%). The anatomic location of injuries was supported by a recent investigation of the injury profile of Swedish tennis players over a 2-year period (20). Other studies have confirmed that lower extremities predominate for the acute injuries, whereas chronic complaints are more common in the upper extremity.
The senior author investigated elite junior tennis players (15-18 years of age) at the United States Tennis Association (USTA) National Junior Championships (23). Based on a questionnaire, only 23% of girls and 45% of boys reported no injury that kept them from playing for 1 week or more, whereas 53% of girls and 29% of boys noted more than one injury in the past.
Low back pain was the most common ailment for both genders (47% of girls, 31% of boys) followed by shoulder pain. Thirty-five percent of junior tennis players complained of shoulder pain at some point in time, whereas more than 50% of older players and elite athletes note shoulder pain at some point in their career (23,24).
Although there was no significant difference in the overall injury rate between boys and girls, there was a difference in the distribution of injuries. Girls sustained more injuries to the feet, leg, and wrist, whereas boys more commonly injured the ankle, groin, and hand (23).
Back pain is very common in tennis players and was identified as the most common injury in junior tennis players (20). Forty-seven percent of female and 31% of male tennis players reported low back pain (currently or in the past), and low back pain has been reported in up to half of all professional players (24).
Many cases of low back pain in players are muscular in nature. These players often complain of a shorter duration of pain, with discomfort usually being located in the paraspinal musculature away from the midline.
Rest, physical therapy, and anti-inflammatory medications are appropriate treatment options for muscular discomfort in the back.
Neurologic complaints, such as numbness, tingling, or weakness of the legs, are not seen with muscular-type discomfort and should warrant further investigation if noted. Persistent back pain or back pain that is not responsive to conservative measures should also be investigated.
In the younger player, spondylolysis or spondylolisthesis is more common, whereas in the older player, intervertebral disc degeneration, disc herniation, and facet arthrosis may occur.
Overuse is the major contributor to back injury in tennis players. In particular, back extension, such as seen during the service motion, is thought to be a main contributor to the development of pars lesions. The reported incidence of symptomatic defects of the pars ranges from 15% to 47% in the younger athletic population (13).
Players with spondylolysis will often complain of axial/midline low back pain, and some will report radiation to the gluteal area or proximal lower extremity. The onset of pain may begin after an acute injury; however, it is more often gradual, with mild symptoms being present for some time. Pain is often exacerbated by back extension during the service motion.
Treatment of spondylolysis and low-grade spondylolisthesis in the tennis player is typically nonoperative and includes prolonged periods of rest in addition to physical therapy. Some clinicians prefer to place athletes with spondylolysis in a thoracolumbosacral orthosis or Boston brace to immobilize the low back to theoretically improve healing rates. This is controversial, however, because some evidence does support improved healing rates, whereas other studies do not, and compliance can be challenging in this group (see Chapter 45, Thoracic and Lumbar Spine). Players who do not respond to nonoperative treatment, as well as those with high-grade spondylolisthesis, may be surgical candidates.
ABDOMINAL MUSCLE STRAINS
Abdominal muscle strains are one of the most tennis-specific injuries and occur at all levels of competition.
Most injuries in tennis involve the rectus abdominis contralateral to the dominant arm (30), usually occurring during the tennis serve.
With the open stance strokes now prevalent in tennis, there is an increased incidence of oblique muscle injuries reported as well (29).
Trunk rotation and flexion and lumbar extension are critical components of the serve, placing large forces on the abdominal wall musculature. Consequently, the most common injury mechanism of the abdominal muscles in tennis players involves a forced concentric contraction of the abdominal musculature when the spine is completely hyperextended, as seen during the tennis serve (29).
With current open stance mechanics, more abdominal muscle activity is used for racquet speed generation and force to hit the ball harder, placing great strain on the abdominal muscles, putting these muscles at risk of strain injury.
The typical presentation for an abdominal wall muscle injury is a competitive player complaining of acute nondominant abdominal wall pain worsened by the service motion.
Treatment of abdominal muscle injury in the tennis player includes rest with or without cryotherapy followed by rehabilitation exercises (30).
Of upper extremity injuries, the shoulder is the most commonly injured in tennis (10).
The shoulder has the most motion of any major joint in the body, and this motion comes at the expense of stability. A careful balance between mobility and stability is necessary to maximize performance. Increased range of motion, particularly shoulder external rotation for serving, is beneficial for the tennis player who is trying to generate maximal velocity and spin with their strokes. Too much motion may result in increased reliance on soft tissues for stability, which may break down and result in shoulder instability. Many structures about the shoulder may be injured in tennis.
Rotator cuff inflammation is common in tennis players of all levels (10). It usually occurs as a result of repetitive overhead serving motions.
Symptoms include lateral shoulder pain with activity or at rest, pain with active arm abduction, or pain with internal/external rotation of the shoulder. Tennis players particularly complain of pain while serving and hitting overheads or high volleys.
Although rotator cuff inflammation may be the result of overuse, or outlet impingement, it may also be seen in other situations, such as rotator cuff tears, instability or microinstability, superior labral anterior to posterior (SLAP) injuries, internal impingement, glenohumeral internal rotation deficit (GIRD), SICK scapula (see later section, “The Tennis Player’s Shoulder”), shoulder stiffness, os acromiale, or scapular dyskinesis.
It is incumbent upon the tennis physician to determine the cause of rotator cuff inflammation and correct the cause. As such, if the cause is treated, the symptoms of rotator cuff inflammation will go away.
Initial treatment includes rest and rehabilitation, with specific emphasis not only shoulder motion (usually posterior capsular tightness), but also on rotator cuff strengthening and scapular stabilization muscle exercises (discussed later). Nonsteroidal anti-inflammatory medications may help with the pain to assist in rehabilitation, as can injectable corticosteroids.
Aggressive treatment of rotator cuff tears is important in tennis players; Sonnery-Cottet et al. (49) have shown that repair of smaller rotator cuff tears results in a higher rate of return to tennis play as compared with players who have undergone repair of larger rotator cuff tears.
Biceps tendonitis is another common complaint in tennis players and may be due not only to the overhead service motion but also the pronation/supination motions of the forearm required for forehands and backhands. The biceps may also become inflamed when the rotator cuff is inflamed and/or there is rotator cuff dysfunction as a result of strain, tendinopathy, or tearing. The biceps may become impinged
by the humeral head and acromion or due to its proximity to the inflamed rotator cuff. The biceps may also become inflamed when there is a concomitant SLAP lesion and/or coracoid impingement.
Players may complain of pain in the anterior aspect of the shoulder and be point tender in this area.
Treatment again consists of rest and shoulder rehabilitation. Oral anti-inflammatory medications have a role in the treatment of biceps tendonitis, whereas the use of injectable corticosteroids remains controversial.
The Tennis Player’s Shoulder
Although scapular dyskinesis and capsulolabral changes within the overhead athlete’s shoulder usually do not directly cause symptoms, they can combine in various ways to cause dysfunction and pathology in the shoulder.
These changes take time to develop and are therefore usually seen in players who participate in tennis on a frequent basis and over a long period of time.
Alterations in scapular motion or position can significantly affect overall glenohumeral biomechanics, as the scapula is critical in shoulder function.
The term “SICK scapula” was introduced to describe a pathologic state of the scapula seen in overhead athletes that is characterized by (a) scapular malposition, (b) inferior medial border prominence, (c) coracoid pain and malposition, and (d) kinesis abnormalities of the scapula (9,22).
Clinically, this syndrome can be recognized by a drooping shoulder on the player’s dominant side, along with scapular asymmetry on inspection. The scapular asymmetry can be further elucidated by slowly adducting the abducted shoulder or with repeated slow forward elevation as the hands are brought from the side to eye level and back down again.
Players may complain of anterior, posterior, or superolateral shoulder pain.
A careful history and physical exam should be undertaken to recognize these constellation of findings instead of attributing the player’s pain to other isolated lesions.
It has been recognized that tennis players develop an increase in external rotation of the dominant shoulder at the expense of internal rotation, leaving the total arc of shoulder rotation unchanged (5).
When there is a greater loss of internal rotation than gain in external rotation and the difference between the dominant and nondominant arm in internal rotation is greater than 25 degrees, then the potential for injury is considered greater and falls under the umbrella of GIRD (8,9).
Kvitne and Jobe (25) initially proposed that repetitive loading in the 90/90 position (late cocking phase of the tennis serve) caused microtrauma to the anterior shoulder capsular structures and the anterior labrum, causing subtle anterior instability. This instability allows the humeral head to translate anteriorly, bringing the greater tuberosity of the humerus and the rotator cuff in close proximity to the posterior glenoid.
This was one theoretical etiology of internal impingement (56), where the undersurface of the posterosuperior rotator cuff (supraspinatus and infraspinatus) may impinge between the humeral head and the posterosuperior rim of the glenoid. This damages the rotator cuff tendons and may also lead to posterior superior labral pathology.
Players usually complain of pain in the posterior shoulder with overhead activity.
Alternatively, this anterior instability could also cause overuse of the rotator cuff by trying to maintain shoulder stability.
More recently, basic science research has shown that posterior capsular contracture results in posterior shoulder tightness and internal rotation contracture and this contracture results in altered humeral head motion, resulting in internal impingement (7).
Posterior capsular contracture as a result of posterior rotator cuff inflammation or hypertrophy of the posterior inferior glenohumeral ligament (IGHL) results in altered humeral head motion in the 90/90 position.
The humeral head moves in a posterior and superior direction in the 90/90 position with posterior IGHL contracture, leading to increased posterior superior labral wear (including SLAP tears), internal impingement, and possibly SLAP tears through the “peel back” mechanism (7,8).
The time of greatest risk for progression of pathology is when the player’s GIRD exceeds the external rotation gain (8).
Treatment of these shoulder pathologies is usually nonoperative initially.
Rehabilitation exercises should focus on the inciting factors, such as the posterior capsular tightness and any scapular dyskinesis that may be present. Posterior capsular stretching exercises include the “sleeper stretch” and “cross-body stretch” (12), whereas scapular dyskinesis can be addressed by a number of exercises that specifically target the scapular stabilizers (9).
Restoration of rotator cuff muscle balance and proprioceptive exercises are also important parts of the rehabilitation protocol (12).
Should nonoperative management fail to improve symptoms, surgical management includes repairing the SLAP lesions, if present (8), and possibly cutting the posterior IGHL to gain internal rotation.
One investigation reported good outcomes in patients undergoing combined SLAP and rotator cuff repair (55).