As we identified in part one, there are a phenomenal number of muscles and joints that must work together in a coordinated manner when throwing. This means if there is one small muscle or joint that isn’t working efficiently another will be exposed to additional load and this is when an injury can occur…



In part one we discussed the complexity of the biomechanics of throwing. From that, we know there are a few common phases where dysfunction can occur. Injuries are likely to occur when:

  • There is poor timing of pelvic and trunk rotation; which changes the way energy is transferred from the lower body to the throwing arm. This can place increased stresses on the shoulder and elbow.
  • The abdominal and oblique musculature is placed on stretch. This commonly occurs on two occasions; when there is a delay between pelvis and trunk rotation and with hyperextension of the lumbar spine. Again, this changes the way load is transferred and can increase stress through the abdominals, obliques, shoulder and elbow.
  • There is dysfunction of the shoulder girdle muscles. These muscles must work together to stabilize and properly position the scapula (shoulder blade) for the appropriate action of the humeral head (arm). This dysfunction of the musculature around the scapula can increase the load on anterior shoulder stabilisers, therefore making them more susceptible to injury.
  • When the elbow is flexed near 90°, the large distance of the forearm, hand and ball from the longitudinal axis of the upper arm resists the shoulder muscles ability to internally rotate the shoulder. By reducing elbow flexion (ie. if elbow extension begins at the end of the arm cocking phase), resistance is reduced which allows greater shoulder internal rotation velocity.

Essentially with throwing, adverse loading will most likely lead to the overload of either the shoulder or elbow. So, what are the most common shoulder and elbow injuries?!


There is a high proportion of shoulder injuries in athletes involved in overhead throwing sports (ie. cricket and baseball). Common injuries include (but are not limited to):

Ulnar collateral ligament overload/tear Tension through the ulnar collateral ligament provides nearly half of the resistance to the valgus torque placed on the elbow. Flexor and pronator muscles in the forearm contribute to the remaining varus torque. Consequently, when these muscles become fatigued the load on the ulnar collateral ligament may be even greater, further increasing the risk of injury to the ligament. At the end of the arm cocking phase, the shoulder is at maximum external rotation, elbow is flexed to 90° and the forearm is in a valgus position. To resist this, a large varus torque must be produced.
Avascular necrosis, osteochondritis dissecans or osteochondral chip fractures Compressive forces through the radial head and humerus secondary to the significant valgus torque placed on the elbow. At the end of the arm cocking phase.
Ulnar nerve compromise Friction/tension/compression of the nerve which can lead to irritation and inflammation of the nerve as it passes through the elbow. Arm cocking, acceleration and deceleration phases.
Posterior elbow impingement Rapid elbow extension can cause impingement of the olecranon into the olecranon fossa. Arm acceleration phase


Along with the elbow, the shoulder is extremely susceptible to injury in overhead throwing athletes. Common injuries include (but are not limited to):

Rotator cuff tear Load in excess to what the muscle(s) is/are able to resist. Often secondary to excessive amount of distraction, horizontal adduction and internal rotation at the shoulder during arm deceleration.
Labral tear Translation, subluxation and compression of the humeral head can cause forceful entrapment of the labrum between the humeral head and glenoid, resulting in the labrum tearing. During arm acceleration and deceleration phases the humeral head is placed under forces that increases load through the labrum.
Impingement Inability to create enough force to control arm deceleration, therefore the humerus can translate superiorly and impinge structures. During arm deceleration, large inferior forces and adduction torques are produced at the shoulder.
Multidirectional instability Repetitive loading and stretching of the joint throughout many ranges. Throughout arm cocking, arm acceleration and arm deceleration, extremes of ranges are needed through the shoulder.


Throwing is a complex biomechanical movement requiring the coordination of multiple joints and muscles. If there is dysfunction with one aspect of a throw, it is most likely the shoulder and/or elbow will be subject to the additional load. For more information, please call (03) 5229 3911 or email; alternatively you can book an appointment online with one of our Physiotherapists.

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