The overhead throwing motion subjects the elbow to a predictable pattern of forces, including medial tension, lateral compression, and posterior shear, that in turn result in a predictable pattern of injuries. Careful history taking, thorough physical examination, and judicious diagnostic imaging allow clinicians to correctly diagnose ulnar collateral ligament (UCL) injury. Athletes with UCL injury complain of acute or chronic medial elbow injury, resulting in decreased throwing effectiveness, with loss of control and/or velocity. Magnetic resonance imaging is the gold standard for diagnosis, but stress ultrasound rapidly is becoming an important adjunct, particularly in diagnostically challenging situations.
The overhead throwing motion results in a predictable pattern of stresses across the elbow joint (tension medially, compression laterally, and shear posteriorly), which may overwhelm the static and dynamic stabilizers and result in injury.
In particular, the medial tensile stresses can exceed the tensile strength of the ulnar collateral ligament (UCL) and result in acute or chronic injury.
History of UCL injury typically is acute or insidious decreased throwing effectiveness with symptoms exacerbated by the late cocking and early acceleration phases of throwing and localized directly to the course of the anterior band of the UCL.
Physical examination is characterized by tenderness over the anterior band of the UCL with positive milking and moving valgus stress tests and can be confirmed with magnetic resonance imaging and stress ultrasound evaluation.
The clinician caring for the overhead throwing athlete must combine a thorough history, comprehensive physical examination, and judicious diagnostic imaging to confirm UCL injury and rule out alternative or concomitant medial elbow pathology.
The overhead throwing motion is a complex series of movements involving the lower extremity, core/trunk, and upper extremity, with the sequential transfer of energy through this kinetic chain toward the wrist and hand. , The stress transferred across the elbow joint during this activity can overwhelm the dynamic and static stabilizers of the elbow. As a result, throwers may incur a characteristic pattern of both acute and chronic elbow injuries, including ulnar collateral ligament (UCL) injury. Based on an understanding of the anatomy and biomechanics of the elbow joint and a thorough history and comprehensive physical examination, the clinician can distinguish UCL injury from other medial elbow pathology common among throwers. Once UCL injury is suspected, it can be confirmed by the judicious use of appropriately selected diagnostic imaging, thereby allowing the clinician to formulate a precise, evidence-based treatment strategy.
Anatomy and biomechanics
Proper diagnosis and treatment of elbow pathology in the throwing athlete require a firm understanding of the anatomy and biomechanics of the joint. The elbow joint is composed of 3 articulations: the proximal radioulnar joint, the ulnohumeral joint both anteromedially and posteriorly, and the radiocapitellar joint laterally. These articulations allow for both flexion/extension of the elbow and pronosupination of the forearm to occur and each may be a site of pathology in the overhead thrower. At low flexion angles (<20°), bony congruity of the joint provides primary stability as the coronoid process of the ulna articulates with the coronoid fossa of the humerus anteriorly and the olecranon process of the ulna articulates with the olecranon fossa posteriorly. At higher flexion angles, stability is provided primarily by the static and dynamic soft tissue structures crossing the joint, including both muscles and ligaments. Between 20° and 120°, the primary stabilizer against valgus stresses is the anterior band of the UCL complex. , , At flexion angles greater than 120°, stability is provided primarily by the posterior band of the UCL. , Most throwers maintain elbow flexion of approximately 80° to 110° during throwing, highlighting the critical importance of the anterior band of the UCL, which may be divided further into reciprocally tightening anterior and posterior bundles. , Additional secondary stability is provided by dynamic contraction of the flexor-pronator musculature originating from the medial epicondyle as well as the elbow joint capsule. The clinician should furthermore be familiar with the course of the ulnar and medial antebrachial cutaneous nerves, because they may be associated with UCL injury and its treatment.
The throwing motion subjects the elbow to tremendous forces, which threaten to individually overwhelm the static and dynamic stabilizers, described previously. Fatigue and injury to 1 stabilizer may lead to a cascade of further injury to the joint. The throwing motion has been described based on the baseball pitch and traditionally has been divided into 6 phases that occur in less than 2 seconds. Maximal forces across the elbow joint are experienced during the late cocking and early acceleration phases, where the elbow may achieve angular velocity of 3000° per second. A single pitch may result in a 64-N/m valgus torque, which is twice the ultimate strength of the anterior band of the UCL alone of 32 N/m, again highlighting the critical coordination of multiple stabilizers in preventing elbow injury during throwing. These stresses result in a characteristic pattern of forces across the elbow, which can lead to the pattern of pathology subsequently seen: the medial elbow is subjected to tensile stresses, the lateral elbow to reciprocal compressive forces, and the posterior elbow experiences shear forces. As a result, the clinician must be cognizant of and closely examine each of these areas as a potential primary source of pathology in the throwing elbow.
The evaluation of an overhead throwing athlete with concern for UCL injury begins with a thorough history. That history should incorporate questions that are unique to throwers in order to confirm the presumptive diagnosis and rule out alternative or concomitant injuries. A majority of UCL injuries represent some combination of acute and chronic injury. These athletes describe preexisting or prior episodes of medial elbow pain that has worsened with a more recent event. A minority of athletes present with a clear history of a sudden, acute pop and medial elbow pain experienced with a single pitch. Depending on the acuity of injury, some throwers’ chief complaint may not involve pain, because some athletes instead complain primarily of tightness or loss of effectiveness. Decreased effectiveness may occur as a result of diminished accuracy or declining velocity. The location, quality, and severity of symptoms should be identified as precisely as possible. The onset of symptoms, timing with respect to activity, and duration should be questioned and defined carefully. Timing with respective to activity should be defined as occurring immediate at the outset of throwing, insidiously over time, or after conclusion of throwing. Modifying factors (both aggravating and relieving), associated signs or symptoms, and prior treatments should be identified.
Additional questions unique to throwing athletes and their particular sport should supplement the standard history. Several points are of particular interest in throwers with concern for UCL injury. A patient’s age with respect to skeletal maturity is critical because it may have an impact on the pattern of injury observed, whether failure occurs at the level of the physis or at the ligament itself. Hand dominance should be identified and whether or not it changes with throwing, batting, or activities of daily living in order to provide full functional context for injury. Frank instability and debilitating weakness are reported infrequently. The presence of neurovascular symptoms, including numbness, tingling, weakness, and temperature sensitivity/intolerance, also should be established for all athletes. Although UCL injury may be encountered more frequently in baseball pitchers, it also may be seen in other baseball players as well as softball players, javelin throwers, and American football quarterbacks. The clinician should know and understand the sport and position played by the athlete and their inherent demands. More specifically for pitchers, the discussion should include typical appearances per week (across all teams played for), number of pitches thrown, number of innings pitched, typical/target velocity, the types of pitches thrown, and which are associated with symptoms. The specific phase of throwing in which symptoms are experienced also is important for establishing an accurate diagnosis, and the patient can be encouraged to simulate the throwing motion if helpful. In order to formulate an appropriate treatment plan, the patient’s level of competition (amateur, high school, collegiate, or elite/professional) should be discussed as well as desire to continue/future goals for activity. The timing with regards to an athlete’s season or upcoming major competitions may inform this decision making further. Finally, any previous injuries or surgeries to the ipsilateral upper extremity as well as the remaining kinetic chain should be confirmed.
With concern for UCL injury, physical examination of the throwing athlete should not be limited to the elbow alone. The athlete should be looked at holistically. A thorough and comprehensive examination should be undertaken, with the standard inclusion of inspection, palpation, range of motion, strength and sensation testing, and special provocative maneuvers. The entirety of the kinetic chain should be evaluated, including the lower extremities and core to identify any deficiencies, which may be contributing to the athlete’s complaints. The neck and cervical spine always should be evaluated, particularly if history reveals neurovascular complaints. Finally, both upper extremities should be examined. The authors advocate for examining the contralateral extremity first, to establish baselines while cognizant that throwing athletes may demonstrate asymptomatic/adaptive asymmetries. Both shoulders and scapulae should be evaluated comprehensively as if they were the source of the primary complaint with attention to range of motion, strength, and provocative maneuvers. Differences in range of motion at the shoulder are particularly common in throwers. Although throwers may demonstrate increased external rotation and decreased internal rotation in their throwing arm, total arc of motion should remain equivalent to the nonthrowing arm. Pain or irregularity in any joint along the kinetic chain should prompt a full, thorough, comprehensive examination of that joint. The authors typically evaluate the painful elbow last, so as not to induce premature guarding while examining the remainder of the athlete’s kinetic chain. The remainder of this section focuses on examination of the throwing elbow specifically, but the same principles should be applied to any joint of concern in the athlete with a throwing elbow complaint.
An athlete should be inspected in shorts and free of sleeves or other clothing so that the entirety of the skin and the patient’s station can be assessed clearly. In throwing athletes with elbow complaints and a concern for UCL injury, ecchymosis is uncommon and typically seen only with higher-energy, direct trauma to the limb. Similarly, swelling of the joint is uncommon but, if present, often may be best evaluated at the lateral soft spot in the triangle formed by the lateral epicondyle, olecranon, and radial head. If a patient reports a prior history of traumatic injury or surgery, the presence and location of any surgical scars should be noted so that they can be accounted for in any surgical planning.
Palpation should be systematic, with the primary purpose of further localizing the thrower’s chief complaint. The authors advocate careful palpation of the medial epicondyle, the flexor-pronator mass, the ulnohumeral joint/ course of the anterior band of the UCL from the sublime tubercle to the base of the medial epicondyle, the borders of the olecranon, and the radiocapitellar joint. Injury to any of these structures generates discomfort along the anatomic course of the structure. Crepitus, warmth, or tissue defects also should be noted wherever present. Precise localization of the point of maximal tenderness is critical to arriving at the correct diagnosis.
Range of Motion
Range of motion of the elbow should be compared with the contralateral extremity. Presence of a flexion contracture is common among high-level throwing athletes in their dominant, throwing arm and may be asymptomatic. There should be no pain, however, at the extremes of motion with a flexion contracture. Pain at terminal motion, in particular, posterior or posteromedial with terminal extension, may indicate posteromedial impingement, posterior loose bodies, or olecranon stress pathology. The forearm should be evaluated for pronosupination deficits or blocks in comparison to the contralateral limb, because this may be indicative of intra-articular pathology. The carrying angle of the elbow also should be assessed at this time. The normal elbow exhibits cubitus valgus of 5° to 15°, although variation has been reported between the dominant and nondominant extremities as well as between male athletes and female athletes.
All muscles crossing the elbow joint should be assessed with standard manual muscle testing. Particular attention should be paid to the function of the musculature originating from the medial epicondyle and its role in reproducing the patient’s chief complaint. Resisted finger/wrist flexion and forearm pronation should be evaluated carefully, because weakness and pain may indicate flexor-pronator pathology. Resisted finger/wrist extension, forearm supination, and elbow flexion and extension should be assessed as well to evaluate for concomitant pathology. Hand intrinsic strength should be evaluated as a means of identifying ulnar nerve pathology, although weakness typically is present only with advanced or chronic compression.
Neurologic and vascular evaluations are necessary components of any elbow examination in the throwing athlete. Sensation to light touch should be assessed in the peripheral nerve distributions of the medial antebrachial cutaneous, lateral antebrachial cutaneous, radial, superficial radial, posterior interosseous, median, anterior interosseous, and ulnar nerves. Decreased sensation in the fifth and ulnar half of the fourth digits suggests ulnar nerve pathology. The ulnar and radial pulses also should be palpated and distal capillary refill in the nail beds of all digits should be evaluated to confirm adequate dual blood supply to the hand. Trophic changes should be noted if present. As discussed previously, the ulnar nerve often is given special consideration in throwers with medial elbow complaints. The presence of Tinel sign should be evaluated along the course of the ulnar nerve and its location documented. Finally, studies suggest that asymptomatic ulnar nerve subluxation can occur in the general population, but pain radiating distally with tingling in the fourth and fifth digits may suggest symptomatic subluxation.
Special Provocative Maneuvers
Finally, several specific provocative maneuvers have been described aid in diagnosing pathology in the thrower’s elbow. These maneuvers allow clinicians to hone their diagnosis more precisely and rule out concomitant or alternative pathology. Two maneuvers commonly are utilized for evaluation of the anterior band of the UCL: the milking test and moving valgus stress test. In the milking Test ( Fig. 1 ), the patient’s shoulder is abducted and externally rotated and the examiner grabs the ipsilateral thumb and milks it in order to place a valgus force across the elbow thereby replicating the stresses of throwing. The complementary maneuver, the moving valgus stress test ( Fig. 2 ), is performed by applying a valgus stress across the elbow in a similar fashion and dynamically flexing and extending the elbow between 30° and 120° of flexion in order to reproduce the late cocking and early acceleration phases of throwing. These tests are positive if they elicit pain and apprehension that the patient localizes to the anterior band of the UCL and underlying ulnohumeral joint. Pain localized elsewhere should suggest alternative diagnoses. Furthermore, gross laxity of the joint is uncommon even in the presence of complete UCL injury and is not necessary for diagnosis of UCL injury. As discussed previously, the flexor-pronator musculature is evaluated specifically with resisted wrist flexion and forearm pronation, and flexor-pronator strain or injury generates maximum tenderness approximately 1 cm distal and anterior to the medial epicondyle. The articulation of the olecranon within the olecranon fossa, which may be a source of pain in valgus extension overload (VEO) with posteromedial impingement, can be evaluated by the arm bar test ( Fig. 3 ). The examiner pronates the patient’s forearm, extends the elbow, and abducts and maximally internally rotates the shoulder all with the patient’s involved extremity resting on the examiner’s shoulder and the olecranon facing the ceiling. The examiner then applies a downward force on the distal humerus to produce maximal extension/hyperextension of the patient’s elbow. A positive arm bar test is characterized by pain within the olecranon fossa/along the border of the olecranon, which replicates the athlete’s complaint in the ball release/follow-through phases of throwing. Complaints localized to the radiocapitellar joint due to the compressive lateral forces of throwing can be assessed further with the active radiocapitellar compression test. The examiner asks the patient to actively pronate and supinate the fully extended elbow. A positive test reproduces lateral symptoms of pain and crepitation. Finally, for patients with history or prior examination findings suggestive of ulnar neuropathy, the ulnar nerve may be evaluated further with the elbow flexion test ( Fig. 4 ). The examiner positions the thrower’s involved extremity in the fully abducted, externally rotated position while flexing the elbow, pronating the forearm, and extending the wrist. The position then is held in place for 30 seconds and a positive test is characterized by the reproduction of pain along the ulnar nerve and/or the reported development of sensory changes/paresthesias.
Imaging of the throwing elbow
Some diagnoses in the thrower may be made based on a thorough history and comprehensive physical examination; however, diagnostic imaging often is valuable to confirm the diagnosis and rule out concomitant pathology. As in most musculoskeletal complaints, plain radiography typically is the initial imaging study obtained. As in other joints, plain radiographs of the elbow can provide the clinician with significant information regarding loss of joint space, osteophyte formation, loose bodies, calcifications, osteochondritis dissecans lesions, cystic changes, and fractures. Radiographs of the contralateral elbow often are valuable for comparison; as discussed previously, throwers may develop asymptomatic, adaptive changes in their dominant, throwing arm. In skeletally immature throwers, all physes and epiphyses should be methodically evaluated for widening and fragmentation. For some diagnoses, plain radiography may be sufficient. In other cases, however, advanced imaging in the form of stress radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US) play a critical role for management of the throwing athlete.
The plain radiographs of UCL injury often are unremarkable but medial soft tissue calcifications, radiocapitellar joint chondrosis, and posteromedial osteophytes also may be observed ( Fig. 5 ). , Given the role of the anterior band of the UCL as the primary stabilizer to valgus stress, valgus stress radiographs techniques have been described using anteroposterior (AP) radiographs while the elbow is stress in approximately 20° to 30° of flexion. , , With stress radiography, 0.4 to 0.6 mm or greater of ulnohumeral joint opening with applied valgus stress has been reported to be indicative of UCL injury. , Stress imaging must be interpreted with care and correlated with the athlete’s history and examination because some elite throwers have been shown to have asymptomatic, increased joint gapping in their throwing arm. The gold standard for diagnosis of UCL injury is MRI with or without intra-articular gadolinium. , , The anterior band of the UCL is best appreciated on coronal sequences running from the base of the medial epicondyle to the sublime tubercle of the ulna. T2-weighted magnetic resonance (MR) sequences often best reveal UCL injury with discontinuous fibers, increased signal intensity within the ligament substance, and/or retraction of a completely ruptured ligament ( Figs. 6 and 7 ). , Chronic injury may present as intraligamentous hyperintensity, ligament thickening, and plastic deformation, resulting in a redundant ligament with reduced functionality. , Intra-articular gadolinium has been reported to dramatically increased the accuracy, sensitivity, and specificity of MRI for the diagnosis of UCL injury, in particular, partial injuries. , Elite throwers may be resistant to the injection of contrast into their throwing elbow, and although unenhanced MRI has been reported to have extremely high sensitivity for full-thickness UCL tears, sensitivity for partial tears has been reported as low as 14%. MR classifications of UCL injury recently have been published by Joyner and colleagues, Podesta and colleagues, and Ramkumar and colleagues. Although the clinical application and prognostic value of each of these systems remains undefined, they allow clinicians to describe both the severity and anatomic location of injury precisely in a common system. Ramkumar and colleagues classification has been reported to have high interobserver and intraobserver reliability. Although invaluable to the clinician, MR does remain a static examination that can be expensive, invasive, and time consuming. In contrast, stress US (SUS) provides rapid, low-cost, noninvasive, nonradiating examination for UCL injury with the ability to dynamically stress the joint at a resolution that equals or exceeds that of MRI. A proliferation of SUS-related literature has demonstrated the increasing role of this modality in the evaluation of patients with UCL injury. , , , Just as asymptomatic abnormalities may be appreciated on plain radiographs and MRI for throwers, ligament thickening, intraligament calcifications, and hypoechoic foci have been described for SUS. Similar to MRI, UCL injury is diagnosed with ligament fiber disruption, loss of ligament tension, and anechoic fluid within a tear. The significant added value of SUS is to dynamically assess the function of the UCL by measuring the ulnohumeral joint space with applied valgus stress at virtually any flexion angle. Furthermore, comparison to the contralateral arm easily can be obtained. Ulnohumeral joint space typically is measured in both arms with and without applied valgus stress. A growing body of literature and work performed at the authors’ institution in a 10-year longitudinal study of 368 asymptomatic major league baseball pitchers as well as cadaveric work has led to using 1.5 mm of increased joint space with valgus stress as indicative of UCL injury ( Fig. 8 ). , , , As with stress radiography, however, asymptomatic increased joint gapping exists among elite throwers and any imaging finding must be correlated with history and physical examination. Full-thickness UCL tears may result in even greater observed ulnohumeral instability, with mean increase of 3.3 mm in ulnohumeral joint space with valgus stress. Roedl and colleagues has reported that SUS can further increase the sensitivity, specificity, and accuracy of MRI for a host of medial elbow diagnoses common among throwing athletes, including UCL injury. SUS, particularly in combination with MRI, can be of particular value to the clinician in athletes presenting with partial UCL injury or recurrent UCL injury after prior reconstruction.