Elbow injuries are an increasingly common injury for children and adolescents involved in throwing sports, such as baseball or softball, as well as other overhead sports, such as football, tennis, and javelin, and in gymnastics, where significant forces are regularly applied across the joint. Along with the increase in the popularity of these sports, factors, such as overuse, poor mechanics, inadequate rest, and pitch selection, have been cited as causes for the rise in the number of these injuries (7,13,16,18,23). Typical causes of elbow pain include acute traumatic injuries, as well as chronic overuse injuries that result from the repetitive stresses of throwing mechanics. Often, athletes are predisposed to acute injuries because of wear and fatigue caused by chronic overstressing and poor biomechanics.
The bony configuration of the elbow allows flexion-extension and pronation-supination at the ulnohumeral and proximal radioulnar articulations, respectively. This bony articulation provides approximately 50% of joint stability, primarily against varus stress in extension. The anterior joint capsule, ulnar collateral ligament (UCL), and lateral collateral ligament complex provide the remainder of the stability of the joint. The UCL is further subdivided into the anterior, posterior, and oblique bundles, of which the anterior bundle is the most important for stability against valgus stress, and is the primary restraint at lesser degrees of flexion. The posterior bundle is the primary stabilizer at greater flexion, due to its increased tightness at greater than 60 degrees and is functionally more important in overhead throwers (3,6,9,14,15).
There are six primary ossification centers in the elbow of the skeletally immature athlete. Although the order of ossification typically follows the general CRITOE pattern (Capitellum, Radial head, Internal (medial) epicondyle, Trochlea, Olecranon, External (lateral) epicondyle), the age of closure of these physes can be highly variable, and contralateral radiographs are often needed as a comparison. During periods of growth, the adjacent attachment sites for ligaments and tendons are especially vulnerable to stress injury, and apophyseal injuries are not uncommon. The most common sites for apophysitis include the medial and lateral epicondyles and the olecranon (1,11,16).
Stages of Throwing
The baseball pitch is the most common cause of overhand throwing overuse injury. The pitching sequence has traditionally been divided into six phases, which include windup, stride, arm cocking, acceleration, deceleration, and follow-through (1,16 [see Fig.]). These phases are consistent independent of age or the athlete’s level of play, though the joint forces involved in the various stages tend to increase with age and level of competition (5).
During windup, the elbow is flexed, with the shoulder in slight internal rotation, and there is minimal stress through the arm. In the stride phase, the upper body remains relatively still, whereas the lower body generates most of the early motion. The arm cocking phase begins when the ball leaves the player’s glove hand and is sometimes divided into early and late cocking. In early cocking, the motion is primarily in the shoulder. This phase ends when the stride foot lands, and during late cocking, there is further shoulder abduction, maximal external rotation, and increasing elbow flexion and forearm pronation. Forces here are generated in the shoulder, and then transitioned down the arm toward the elbow during the acceleration phase. This phase features internal rotation and adduction of the humerus and rapid elbow extension, which generates tremendous valgus stresses around the medial elbow structures, making it the predominant phase for elbow injury. The anterior bundle of the UCL bears most of the force, whereas secondary structures facilitate the transmission of force. This phase ends when the ball is released from the hand, which also generates significant compression and rotary stresses laterally in the radiocapitellar articulation, whereas triceps contraction puts tensile force on the posterior compartment. This is followed by deceleration and follow-through, during which kinetic energy is dissipated and motion stops (1,3,6,15).
Injury patterns can generally be subdivided based on the location and causative forces involved. Injuries to the lateral elbow are most often secondary to the compression forces across the radiocapitellar joint. Medial elbow injuries, on the other hand, are typically a result of distraction and tension forces from repetitive overuse. Posterior elbow injuries are caused by the sheer stresses generated at the end of the throwing motion, when the elbow is in full extension, generally referred to as valgus extension overload (3,9–11,15).
Panner’s disease is a self-limiting form of articular osteochondrosis of the capitellum or radial head. It was first described in 1927, and was noted for its resemblance to Legg-Calve-Perthes disease. The peak incidence occurs from ages 4 to 8 yr and is more likely in boys due to both the delayed maturation of the secondary growth centers, and the increased susceptibility to trauma associated with childhood activities. Patients typically present with a history of several weeks of symptoms, primarily pain and stiffness of the dominant elbow, with a recent history of mild trauma or overuse. Initial radiographs will show fissuring, irregularity, and fragmentation of the capitellum. These changes are thought to be a result of increased valgus compressive forces across the radiocapitellar joint during a time of increased vulnerability in the immature bone. Repetitive microtrauma may compromise cellular viability within the chondroepiphysis, leading to disordered endochondral ossification.
Physical examination will typically reveal lateral pain with tenderness over the capitellum, limited range of motion in extension, and, less commonly, a small joint effusion and loss of flexion or forearm rotation. Treatment is nonsurgical and is aimed at alleviating symptoms, with a focus on reduction of activities that stress the radiocapitellar joint. Anti-inflammatory medications also may provide significant relief. The natural history of Panner’s disease typically involves the resolution of these radiographic findings and their associated symptoms, and the prognosis is excellent, with no residual pain or deformity (1,9,10,15).
Little League Elbow
The term “Little League elbow” has been used to describe a variety of conditions affecting the elbow in young throwers; however, it most commonly refers to injury to the medial epiphyseal plate due to tension from valgus stress or medial epicondyle apophysitis. Although this injury usually presents with an insidious onset of pain over the medial elbow, as a result of the repetitive stresses of throwing, acute injuries also have been reported. Pain localizes directly over the medial epicondyle, and physical examination will often show loss of full elbow extension and pain with valgus stress. Initial management includes modification of activities, with rest from all throwing for up to 3 months, as well as ice, anti-inflammatory medications, and eventually an interval throwing program (1,8,9,11,14,15,22).
Medial Epicondyle Avulsion Fractures
Acute injuries to the medial epicondyle are more likely to produce an avulsion fracture. Rotational deformity may allow for increased laxity of the UCL, and therefore increased instability of the joint, predisposing athletes to injury. These fractures have historically been treated nonoperatively, even with significant fragment displacement, and the resultant radiographic nonunions were thought to be benign. However, for children active in throwing sports, or who place high distraction forces on the medial elbow (gymnasts, wrestlers, etc.), anatomic reduction and fixation of the fragment may provide more elbow stability, because the UCL complex originates at this site (1,9,11,14,15).
Osteochondritis dissecans (OCD) is an inflammatory disorder of the osteochondral articular surface. Many have drawn comparisons between OCD and Panner’s disease, and some consider them to be along a spectrum of the same disease; however, the age of presentation, radiographic findings, and prognosis differ significantly between the two. The most consistent difference between OCD and Panner’s disease is the age of presentation, with patients under the age of 10 yr typically presenting with Panner’s lesions, while OCD lesions and persistent intra-articular loose bodies are more common in older children.
The biomechanics of throwing predispose athletes to OCD injuries due to abnormal valgus stresses on an immature articular surface during acceleration and follow-through. Weakening of the subchondral bone occurs from microtrauma secondary to compressive forces at the radiocapitellar joint, as a result of tensile stresses on the medial aspect. This results in failure of the subchondral osseous elements, and resorption of the bone at the fracture site leads to separation of the fragment from the underlying bed. The overlying cartilage is then subject to shear stresses, and breaks down, forming fragments and loose bodies.
Patients typically present with insidious, poorly localized lateral elbow pain with throwing, although up to 20% will identify a single traumatic event at the onset of symptoms. There may be associated stiffness and swelling, with loss of range of motion in extension, pronation, and supination. Mechanical symptoms suggest instability or loose bodies, and in some cases, patients may have true locking of the joint. This is usually intermittent and will occur with throwing.
Although magnetic resonance imaging is most sensitive, radiographic findings for OCD lesions will typically involve a focal area of lucency in the subchondral bone, with surrounding sclerosis and a characteristic semilunar rarefied zone (crescent sign). In the capitellum, this typically occurs on the anterior surface. Similar to Panner’s disease, the radial head may become enlarged and irregular in later stages. OCD lesions also may form in the radial head itself, but are more common in the capitellum due to its tenuous blood supply.
Treatment of patients with OCD varies depending on the stage of the lesion, as well as clinical findings. Staging of OCD lesions in the capitellum requires magnetic resonance imaging. Intact, stable lesions can be managed nonoperatively, with 3 to 6 wk of bracing and a gradual return to activity over 3 to 6 months. More advanced lesions, those with symptomatic loose bodies, unstable lesions, and those that do not respond to nonsurgical treatment may require surgical excision of loose bodies and abrasion chondroplasty or subchondral drilling. Radiographic healing typically lags behind improvement in clinical symptoms and should not be used as the primary measure of return to throwing (1,8–11,15,17).
Olecranon Stress Fractures
At the end phase of throwing, with the elbow in full extension, the elbow experiences increased stress on the olecranon due to valgus extension load. This repetitive microtrauma, as well as excessive tensile stress forces from the triceps, has been implicated as the causative factors for stress fractures at the olecranon. Athletes will present with limited and painful elbow extension, pain with resisted triceps testing, and tenderness over the posterior aspect of the elbow. X-rays may show remodeling of the fracture site or a widening of the physis. Conservative management is typically successful, though some data suggest early surgical treatment may reduce the time to resumption of throwing and may aid in cases with associated loose bodies, osteophytes, or other injuries (1,9,11,15).
The development of olecranon osteophytes is another consequence of repetitive valgus extension overload stresses. The osteophytes primarily develop medially, but also can be seen less commonly on the posterior or lateral aspect of the olecranon. These osteophytes can impinge within the olecranon fossa, causing pain, locking, catching, or crepitus in the posterior compartment. Symptoms can be reproduced on physical examination with the valgus extension overload test. The examination also should carefully assess surrounding structures as injuries can occur to neighboring structures, such as the UCL, flexor pronator mass, radiocapitellar joint, and ulnar nerve. Radiographs or CT scans can be used to identify loose bodies and osteophyte fragmentation. Initial treatment should include rest and an interval throwing program. Physical therapy with a focus on dynamic stabilization and strengthening of the flexor pronator mass also can help improve symptoms. Refractory cases may require surgical intervention, with open or arthroscopic resection of osteophytes and removal of loose bodies (1,9,11,15).
The UCL is the primary ligamentous stabilizer of the elbow, and absorbs approximately 50% of the valgus torque imparted by the throwing motion. The forces generated by throwing activities often exceed the failure strength of the UCL, and repetitive stress creates a cumulative microtrauma effect, which can lead to acute ligament rupture.
Acute tears of the UCL usually present with the sudden onset of pain or a popping sensation on one particular throw, whereas chronic injury is more typically associated with loss of ball control, loss of velocity, and early fatigue. Pain is usually isolated to the acceleration phase of throwing, though terminal extension also may exacerbate symptoms in the later stages. Physical examination may reveal a positive “milking test,” in which valgus stress on the elbow while flexed at 90 degrees results in pain, apprehension, or instability. The moving valgus stress test also may be used, in which the examiner applies valgus pressure at the elbow while moving the arm between 70 and 120 degrees of flexion.
In suspected UCL injuries, radiographs should be obtained to rule out associated injuries, and stress views can be combined with contralateral X-rays to examine the degree of laxity. Ultrasound evaluation of an injured UCL may show heterogeneity, thickening, calcifications, or tears, and instability on dynamic stress. MRI arthrogram remains the gold standard test, with 86% and 95% sensitivity for partial and full tears, respectively, and 100% specificity for both.
Partial tears can be treated conservatively, with at least 3 months of rest from throwing, and physical therapy focused on active and passive range of motion. Platelet-rich plasma injections also have been investigated for partial tears, and some preliminary studies have shown increased return to play rates and improvements in symptoms scores.
Complete tears and partial tears that fail conservative treatment should be managed surgically. As the rates of UCL reconstruction have steadily increased, new techniques have been developed, with improvements in overall outcomes and high rates of successful return to previous level of play, though the full recovery process is often up to 12 months or longer.
Although there has been a significant increase in the rate of UCL tears in all throwers, including younger athletes, these injuries are more unusual in skeletally immature athletes due to the relative strengths of the UCL and the apophysis. Repetitive stresses are more likely to cause injury to the weaker apophysis, which does not tolerate the biomechanical stresses of high velocity throwing as well (1,2,9,11,14,15).
Flexor-Pronator Mass Injuries
After the UCL bundle, the flexor-pronator mass absorbs the highest amount of valgus force across the elbow during throwing activities. The muscles act as dynamic stabilizers and help prevent injury to the ligaments through repetitive contraction, predominantly during the acceleration phase of throwing and in wrist flexion during ball release. The originating tendons of the involved muscles are predisposed to injuries in throwers due to their dynamic function. Overuse can lead to inflammation, tendonitis, or tears. Patients will have pain over the origin of the flexor-pronator mass, just distal to the medial epicondyle, worse during the late cocking or acceleration phase. Pain that is more distal or posterior should raise suspicion for UCL injury, and combined UCL and flexor-pronator injuries are not uncommon.
Injuries to the flexor-pronator mass typically respond well to rest, ice, anti-inflammatories, and physical therapy focused on active range of motion. An interval throwing program can begin once pain resolves. Corticosteroid injections can be used in athletes who do not fully respond to initial therapies, though the proximity to the UCL complex makes this less desirable. Platelet-rich plasma (PRP) injections and tenotomy procedures also may be considered, though there is not reliable data for their efficacy. Surgical treatment can be considered when other therapies fail to improve symptoms, though it is rarely required (9,15).
Conservative measures for most throwing injuries include rest from all throwing for a period, in addition to standard treatments, such as ice and anti-inflammatory medications. The amount of time without throwing will vary depending on the particular injury type and the patient’s symptoms, but can be limited to just a few weeks with more minor injuries, or can extend up to 6 months or more with more severe cases, such as advanced stage OCD lesions. Physical therapy during this time should focus on decreasing inflammation, increasing range of motion and flexibility, and supporting tissue healing, as well as lower extremity and core strengthening. Throwers also should undergo a biomechanical throwing evaluation with attention to proper form throughout the phases of throwing. When athletes return to throwing, they should do so through an interval throwing program. These programs provide for a gradual progression back to full activity, starting with a consistent, focused warm-up, and short-distance throwing. The distance is gradually increased and progresses as long as the athlete remains pain-free, does not have a reduction in strength or range of motion, and does not have soreness that lasts longer than 24 hours. Full return to sport should occur only with symptom-free activity in the setting of demonstrated durability, proper mechanics, and appropriate rest (1,9–11,14,15,18).
Risk Factors and Injury Prevention
Given the prevalence and significance of elbow injuries in young throwers, many studies have attempted to identify the risk factors associated with these injury patterns. In a 2014 study, Yang et al. identified several primary factors that predicted an increased risk in elbow injuries. These included pitching more than 8 months out of the year, pitching for multiple teams with overlapping seasons, pitching multiple games per day, pitching on back-to-back days, and pitching while fatigued or with pain. Pitching with fatigue or pain places athletes at the highest risk for injury, with a 7.88 and 7.50 times greater rate of pitching-related injury, respectively, in their study. It has been suggested that the loss of proprioception that accompanies muscle fatigue is a primary contributor to the increased risk of injury (9).
Other proposed injury risk factors include pitch type, velocity, and pitch count. Traditional expert opinion once suggested that the early use of curveballs and other breaking pitches placed youth throwers at a higher risk of elbow and shoulder injury. A number of studies have examined various pitch types as risk factors for injuries to these athletes. Although results vary, biomechanical analysis has shown few kinetic differences between different pitches and demonstrated the greatest joint loads with fastballs and the least with changeups. This suggests that velocity and not pitch type is the primary determinant of stress on the joint and surrounding structures. Additionally, pitchers who throw curveballs at a young age tend to be the better pitchers on a team, and therefore have higher overall pitch counts, confounding many epidemiologic studies. Nonetheless, USA Baseball recommendations state that breaking pitches should not be thrown until after bone maturity (2,5–7,13,16,18,21,23).
The cumulative microtrauma associated with a high quantity of pitches also contributes to the risk of injury. A 2001 study by Lyman et al. (12) found a significant association between the number of pitches per game and pitches per season, and the rate of both elbow and shoulder pain, whereas in 2011, Fleisig et al. (4) found that those pitching more than 100 innings per year were 3.5 times more likely to be injured than throwers with few innings pitched. USA Baseball provides age-related pitch count recommendations, and advises against pitching in multiple leagues, year-round baseball, and pitching at home after pitching in a game (16,21) (see Table).
Davis et al. (3) found that young throwers with good mechanics generated lower torques and joint loads through their throwing motion, whereas a 2014 study by Tyler and Mullaney (20) found that preseason supraspinatus weakness was significantly associated with a 4.58 increased injury risk. These findings suggest that throwers should learn proper mechanics at an early age and work on strength and power as they mature. Other important factors in mitigating risk for young throwers include flexibility, conditioning, and close monitoring for fatigue (18).
Baseball pitchers and other throwing athletes place their elbows under tremendous stresses, making them vulnerable to a number of unique injuries. Skeletally immature throwers in particular are at a greater risk for growth plate and other bony injuries, due to the relative strengths of these tissues and the kinematics involved in throwing. Care should be taken to fully evaluate these injuries based on the particular history and presentation to properly direct treatment and rehabilitation. Patients as well as other athletes, coaches, and families also should be made aware of the significant risk factors for these injuries, especially those regarding pitch limits, proper mechanics, and sufficient rest.
The authors declare no conflict of interest and do not have any financial disclosures.