Our patient’s pronator teres injury occurred at the myotendinous junction, a muscle-tendon transition zone often susceptible to injury. What is unusual for this athletic medial elbow injury is that the patient reported no previous symptoms, and it appears that, though the surrounding muscle may have been fatigued by overuse from the round of golf earlier that day, the pathology was caused by an acute eccentric force. During a golf swing, tremendous forces are put on the entire body, from the lower extremities to the forearm and the fingers. Successful completion of the transfer of energy from the golf club to the ball requires both proper technique and proper functioning of key muscles. Specifically, parameters such as ball positioning, club angle, and wrist control play a major role.6 Altered forearm positioning or swing arc can significantly affect club head velocity and energy transfer without putting more stress on the golfer.7 Therefore, it is easy to understand how prolonged or extended play may fatigue the surrounding elbow muscles, leading to altered technique and increased susceptibility to acute injury. Biomechanical analysis of shoulder motion can provide a helpful baseline for assessing injury-related changes in golf swing and developing specific exercise and rehabilitation programs.8,9Although injury to the pronator teres is rare, sport physicians should be aware that, after a valgus stress or force, bruising and swelling along the medial elbow do not always indicate a medial ulnar collateral ligament (MUCL) tear or medial epicondylitis. The key examination findings that differentiate this injury from a MUCL injury are the exact location of pain, the milking maneuver for MUCL incompetence, and the extensive bruising over the muscle course of the pronator teres. MRI plays a pivotal role in proper diagnosis.4 In addition, MRI allows for evaluation of any concomitant injuries that may be obscuring the clinical presentation.
Successful treatment of such injuries is important for both elite and recreational athletes. With rest and physical therapy, our patient recovered from this rare isolated injury to the pronator teres with complete resolution of symptoms and full ROM. In the literature, we found no other reports of isolated full-thickness myotendinous rupture of the pronator teres or avulsion from the medial epicondyle. Therefore, it is unclear whether the same outcome can be expected with conservative therapy. However, because of the good outcomes for partial-thickness injuries treated conservatively and the lack of robust tendinous tissue to repair at the myotendinous junction, we recommend an initial course of conservative treatment. Sports physicians should be aware of this exceedingly rare injury to the elbow and understand the large forces experienced by the soft tissues of the forearm during the golf swing.9,10
Conclusion
Pronator teres muscle strain is a rare sporting injury reported in cricket and golf players. The elbow experiences a large eccentric force during resisted elbow flexion and pronation. The injury appears to occur when the sporting club or racket strikes the ground during a forceful swing impeding forward progress of the arm. The injury can be confused with a MUCL injury, or exacerbation of medial epicondylitis. Physical examination reveals bruising and tenderness over the course of the pronator teres, often distal to the elbow. Advanced imaging confirms the diagnosis and helps grade the severity of muscle strain. Treatment is often conservative, with return to function and sport after 4 to 6 weeks of rest and restricted activities. The patient in this case report had complete return to sporting function, with no residual weakness or pain.
Am J Orthop. 2017;46(2):E105-E107. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.