Biceps Tendonitis in Baseball Players: Causes, Treatment & Shoulder Physical Therapy

Kathy Ryan-Ceisel, PT MHS | Algonquin Sports PT

Overhead Throwing Expert-Athletic Edge and Wellness

Biceps tendonitis is a common condition that affects overhead throwing athletes, particularly baseball and softball players. The repetitive, high-velocity motion of throwing places significant stress on the structures of the shoulder and elbow. Over time, this stress can lead to irritation and inflammation of the long head of the biceps tendon, a key stabilizer of the shoulder during throwing.

For pitchers, catchers, and other position players who throw frequently, this condition can develop gradually due to repetitive overload, poor mechanics, or underlying shoulder dysfunction. Understanding the causes, symptoms, and treatment strategies for biceps tendonitis is critical for maintaining arm health and preventing long-term injury.

Anatomy and Function of the Biceps with Throwing

The biceps brachii muscle plays an important role at both the shoulder and elbow. It has two proximal attachments:

• Long head of the biceps tendon (LHBT) – attaches to the superior labrum and supraglenoid tubercle of the shoulder

• Short head of the biceps tendon – attaches to the coracoid process of the scapula

Distally, the biceps attaches at the radial tuberosity of the forearm.

The primary functions of the biceps include:

• Elbow flexion

• Forearm supination (turning the palm up)

• Secondary stabilization of the shoulder joint

In baseball throwing mechanics, the biceps plays a critical role in arm deceleration after ball release.

During a high-intent throw:

• The elbow extends rapidly.

• The forearm pronates.

• The shoulder moves into extension.

At this moment, the biceps and posterior shoulder muscles act as the braking system to slow down the arm. This eccentric contraction places significant load on the tendon, especially during the deceleration phase of throwing. Due to repeated stress, the biceps tendon is particularly vulnerable to irritation in throwing athletes.

What is Biceps Tendonitis?

Biceps tendonitis refers to inflammation or irritation of the biceps tendon, most commonly involving the long head of the biceps tendon at the shoulder.

Over time, repeated micro-trauma from throwing can lead to:

• Tendon inflammation

• Microtears

• Tendon degeneration

When the pathology becomes more degenerative rather than inflammatory, it may be more accurately referred to as biceps tendinopathy.

Another important consideration is that biceps tendonitis rarely occurs in isolation. It is frequently associated with other shoulder conditions including:

• Rotator Cuff injuries

• Labrum Injuries - SLAP tears (Superior Labrum Anterior to Posterior)

• Shoulder impingement

• Glenohumeral Internal Rotation Deficit (GIRD)

• Scapular dyskinesis

Dysfunction elsewhere in the shoulder places increased stress on the biceps tendon.

Biomechanics: Why Throwing Stresses the Biceps

The overhead throwing motion places tremendous stress on the shoulder. During throwing, two phases are particularly demanding on the biceps tendon.

Late Cocking Phase

During this phase the shoulder reaches:

• Maximum abduction

• Maximum external rotation

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This 90-90 degree shoulder position can result in a "peel-back" mechanism, causing the biceps anchor on the labrum to experience substantial shear force.

Deceleration Phase

After the ball is released, the arm must slow down extremely quickly.

The biceps contracts eccentrically to control elbow extension, helping to absorb the tremendous forces created during the throw. Over hundreds of repetitions, these forces can lead to cumulative microtrauma within the tendon.

Symptoms of Biceps Tendonitis

Athletes with biceps tendonitis typically experience pain in the front of the shoulder that may radiate down the upper arm.

Common symptoms include:

• Pain or tenderness in the front of the shoulder

• Pain that worsens with overhead activity

• Aching pain that radiates down the upper arm

• Pain with resisted elbow flexion or forearm supination

• Tenderness in the bicipital groove

• Snapping or clicking sensation in the shoulder

Because the bicipital groove is a relatively narrow space, irritation of the tendon can create a cycle of inflammation and friction. As swelling increases, the tendon may rub more against the surrounding bone, leading to further irritation and chronic symptoms.

Causes of Biceps Tendonitis in Baseball

Several factors contribute to the development of biceps tendonitis in baseball players.

1. Overuse and Workload

Repetitive throwing is the most common cause of this injury.

Both throwing volume and intensity contribute to tendon stress. High pitch counts, excessive bullpen sessions, playing multiple positions, and year-round throwing without adequate rest can overload the tendon.

The late cocking and follow-through phases of throwing place significant stress on the biceps through; extreme external rotation, rapid elbow extension and eccentric muscle contraction.

2. Poor Throwing Mechanics

Throwing mechanics that rely heavily on the arm rather than the entire kinetic chain can increase stress on the shoulder and biceps tendon.

Common mechanical issues include:

• Early trunk rotation

• Poor hip-shoulder separation

• Inadequate lower body power

• Throwing primarily with the arm

When the legs and trunk fail to generate adequate power, the shoulder and elbow must absorb more stress.

3. Shoulder Mobility Deficits

Overhead athletes frequently experience a reduction in shoulder mobility, and even minor losses can negatively impact the throwing shoulder. A significant risk factor is the reduction in Total Rotation Motion compared to the opposite shoulder. Achieving symmetry between shoulders is the objective. Pitchers often lose internal rotation because of tightness in the posterior capsule, which changes shoulder mechanics and heightens stress on the anterior shoulder.

4. Muscle Imbalances

Weakness in the muscles that stabilize the shoulder can increase strain on the biceps tendon.

Common contributing factors include:

• Weak rotator cuff muscles

• Poor scapular stability

• Weak posterior shoulder muscles

• Insufficient thoracic mobility

In throwing athletes, the posterior shoulder musculature should ideally be about 67% as strong as the anterior musculature to maintain balance around the joint.

5. Trauma

Although less common, direct trauma can also irritate the tendon.

Examples include:

• Sliding into a base

• Diving for a ball

• Taking an awkward swing

• Sudden forceful pulling motions

These injuries can initiate inflammation that later becomes chronic.

Diagnosis of Biceps Tendonitis

Diagnosis begins with a detailed clinical examination.

A sports physical therapist or sports medicine physician will evaluate:

• Pain location

• Throwing history and workload

• Shoulder range of motion

• Rotator cuff strength

• Scapular control

Several special orthopedic tests may help identify biceps involvement:

If necessary, imaging may be used to confirm the diagnosis or rule out associated injuries.

Common imaging options include an MRI and diagnostic ultrasound.

These tests help identify tendon inflammation, partial tears, or associated labral injuries.

Treatment of Biceps Tendonitis

Most cases of biceps tendonitis in baseball players respond well to conservative treatment.

Relative Rest and Activity Modification

Reducing throwing volume is often the first step. Complete rest is not always required. Instead, throwing may be modified depending on symptoms.

For example:

• A pitcher may avoid mound work

• A player may continue short-distance throws if pain-free

Workload modifications should always be discussed with a therapist or sports medicine professional.

Physical Therapy

Physical therapy plays a critical role in getting athletes back on the field.

Treatment Goals:

Restoring shoulder mobility

• Improving overhead range of motion

• Addressing posterior capsule tightness

• Improving thoracic mobility

Strengthening the shoulder

• Rotator cuff strengthening

• Posterior shoulder strengthening

• Scapular stabilization exercises

• Eccentric training has shown strong benefits for tendon injuries. This helps build tendon strength and resilience.

Manual Therapy and Soft Tissue Work

• May also be used to reduce tissue irritability and to reduce restrictions in the the soft tissue.

• Taping techniques can be used to support muscles and tissues during the healing phase without impeding motion or activity. It can be used in both acute and chronic injuries to facilitate healing and recovery.

Progressive Throwing and Plyometrics

• As strength increases, plyometric exercises can be added to replicate the stresses of throwing through activities involving acceleration and deceleration.

• Progressions might involve progressing from two-handed throws to one-handed throws.

This progression enables the arm to slowly regain its tolerance to acceleration and deceleration.

Return to Throwing Program

Returning to baseball requires careful workload management with a physical therapist or athletic trainer.

A structured return-to-throw program should:

• A gradual increase in throwing distance

• Progression of throwing intensity

• Monitoring of symptoms

• Addressing relevant throwing mechanics to allow power to come from the legs and trunk, reducing stress on the arm.

Understanding a player’s positional demands is also important. The workload of a pitcher is very different from that of an infielder or outfielder. Managing workload includes providing adequate rest and recovery from throwing.

Final Thoughts

Biceps tendonitis is a common overuse injury in baseball players, particularly those who throw at high volumes or intensity. Because the long head of the biceps tendon plays an important role in shoulder stability and arm deceleration, repetitive throwing can place significant stress on the tendon over time.

Early recognition, proper workload management, and targeted rehabilitation are key to preventing this condition from becoming chronic. By addressing shoulder mobility, strengthening the rotator cuff and scapular stabilizers, and refining throwing mechanics, athletes can return to throwing safely while reducing the risk of future injury.

If you have questions regarding shoulder pain or biceps tendonitis, give us a call at 224-505-EDGE or visit our website at www.edge360wellness. com

Athletic Edge and Wellness, Illinois Baseball Edge and 1Top Prospect in Algonquin are your professional throwing partners in baseball/softball performance and arm care: We offer private and team instruction, velocity enhancement, command sessions, throwing form, coaching clinics, Flightscope video assessment, data analytics, physical therapy, performance therapy, normatech recovery, and collegiate recruiting under one roof. Come experience the difference from our pros in the field.