Trying to diagnose pain issues is difficult next impossible. Every individual has a different physical makeup in terms of mobility, range of motion, connective tissue, etc., etc. His pain could simply be due to his physical makeup (shoulder complex).
That being said what stood out to me is his very high elbow slot (I don’t like to use arm slot because I think the path the elbow more accurately describes the motion). There’s nothing wrong with a high elbow slot IF the body (posture) supports it. I don’t see the postural support that I would like to see in your son’s delivery.
Your son has very good extra rotation (looks like almost 180°). This poses the potential for subluxation of the shoulder joint i.e. the head of the humorous wants to move out of the glenohumeral joint. It’s possible that the high elbow slot i.e. elevating the shoulder complex aggravates this.
Something else you mentioned with regard to your son not picking up a baseball from August to January. There have been a number of studies that show that continual throwing of young players creates physical adaptations such as increased range of motion due to actual structural changes of humorous. And it’s speculated that these physical adaptations are what allows more mature pitchers to not only throw harder but to minimize the risk of injury.
This is not to say that players should throw to the extent of creating overuse injuries. It simply means that as would exercising three times a week create a change in the physical mass of muscle so would it create changes in connective tissue and bone structure. In other words continual stress and in this case I’m talking about a positive stress i.e. stress that doesn’t lead to overuse injury will create physical adaptations.
I’m glad you provided some velocity numbers because I would expect your son to have a very good velocity with the amount of extra rotation that he creates. I also believe that with some adjustments in terms adjusting the body posture to better match his arm slot that he could easily add another 5-7 mph and reduce the amount of stress on the shoulder.
Again some educated speculation/guesswork.
Injuries > Shoulder > Shoulder Instability
(Also known as Anterior Instability, Posterior Instability, Inferior Instability, Multidirectional Instability, Recurrent Subluxing Shoulder)
What is shoulder instability?
Shoulder instability is relatively common condition characterized by loosening of the connective tissue (ligaments and joint capsule) surrounding the shoulder joint therefore enabling the bones forming the joint to move excessively on each other.
The shoulder joint is a ball and socket joint. The shoulder blade gives rise to the socket of the shoulder, whilst the ball of the shoulder arises from the top of the humerus (upper arm bone). Surrounding the ball and socket joint is strong connective tissue holding the bones together known as the shoulder joint capsule (figure 1) and its associated ligaments. In addition, a group of muscles known as the rotator cuff cross the shoulder joint and collectively help to hold the shoulder joint in position increasing the shoulder’s stability.
During certain movements of the arm (such as throwing or falling on an outstretched arm), stretching forces are applied to the shoulder joint capsule and ligaments. When these forces are traumatic or repetitive enough, stretching or tearing of the connective tissue may occur. As a result, the connective tissue supporting the shoulder may become loose and unsupportive, allowing the joint to move excessively and resulting in an “unstable” joint. This condition is known as shoulder instability and may result in the upper arm bone (humerus) moving subtly or completely out of the socket during certain arm movements (subluxation or dislocation).
Shoulder instability normally presents in one shoulder. Occasionally, however, it may exist in both shoulders, particularly in those patients who have general ligament laxity (i.e. loose connective tissue), or in those patients who perform repetitive overhead activities on both sides of the body (such as swimmers).
Causes of shoulder instability
Shoulder instability most commonly occurs following a traumatic incident that partially or completely dislocates the shoulder (such as a fall onto the shoulder, or outstretched hand, or, following a direct blow to the shoulder). This frequently occurs in contact sports such as rugby or football (Australian rules). The usual movements involved are a combination of shoulder abduction (side elevation) and excessive external rotation (outer rotation of the humerus) (figure 2).
Shoulder Instability may also occur gradually over time (atraumatically) due to repeated stresses to the shoulder joint associated with repetitive end of range shoulder movements (such as throwing or swimming). This may occur in association with abnormal biomechanics such as poor throwing technique or a faulty swimming stroke and commonly occurs in sports requiring repeated overhead activities such as baseball pitchers, javelin throwers, cricketers, swimmers and tennis players.
Occasionally, shoulder instability may be associated with generalized ligamentous laxity throughout the body. This may be something that is present from birth and is commonly referred to as being ‘double jointed’.
Signs and symptoms of shoulder instability
Patients with shoulder instability may experience little or no symptoms. In atraumatic shoulder instability, the first sign of symptoms may be an episode of the shoulder subluxing (i.e. partially dislocating) or shoulder pain or ache either during, or following, certain activities.
In post-traumatic shoulder instability the patient usually reports a specific painful incident that caused the problem. Commonly the shoulder will have dislocated or subluxed, often with the arm in a position of combined abduction and external rotation at the time of injury (figure 2). Following this incident, the patient may experience pain during certain activities or after these activities with rest (especially at night or the next morning). The patient usually reports that the shoulder has never felt the same since.
Patients with shoulder instability will often notice a clicking, clunking or popping sensation within the shoulder during certain movements. There may be a loss of power in the affected shoulder and a feeling of weakness during certain activities (e.g. overhead activity). Patients may also experience tenderness upon firmly touching the front or the back of the shoulder joint and a feeling of apprehension that the shoulder may dislocate with certain end of range movements (particularly the combination of abduction and external rotation) (figure 2). Patients may also experience pain or a sensation of the shoulder joint moving out of place when sleeping on the affected side.
In severe cases of shoulder instability, patients frequently experience recurrent episodes of subluxation or dislocation of the shoulder. This may be associated with shoulder pain and occasionally, a ‘dead arm’ sensation which typically resolves after a few minutes rest. In these instances or in patients with multidirectional instability, the patient may be able to voluntarily sublux or dislocate the shoulder. In more severe cases, relatively minor activities such as yawning or rolling over in bed may result in a subluxation or dislocation. [/quote]