Shoulder Anatomy

The shoulder is a highly flexible and mobile joint that connects the arm to the torso, enabling a wide range of movements. It consists of three main bones: the humerus (upper arm bone), the scapula (shoulder blade), and the clavicle (collarbone). The shoulder’s stability is provided by the rotator cuff muscles, ligaments, and tendons, which work together to allow for overhead motions, rotation, and lifting. The ball-and-socket structure of the shoulder allows for unparalleled mobility but also makes it prone to injuries such as rotator cuff tears, dislocations, and arthritis. Understanding the shoulder’s anatomy helps to appreciate its complexity and functionality in everyday movement.

Specializing Surgeon

Christopher R. Sforzo, M.D.

Specializing Surgeon

Christopher L. Dillingham, M.D.

Specializing Surgeon

Christopher R. Sforzo, M.D.

Specializing Surgeon

Christopher L. Dillingham, M.D.

Conditions & Treatments

Shoulder Arthritis: Causes, Types, and Symptoms

Shoulder arthritis is a condition where the cartilage in the shoulder joint deteriorates, leading to pain, stiffness, and reduced mobility. It can significantly impact daily activities such as lifting, reaching, or even sleeping comfortably.

Causes of Shoulder Arthritis

The causes of shoulder arthritis can vary, but common factors include:

  • Osteoarthritis (OA): The most common type of shoulder arthritis, caused by gradual wear and tear of the cartilage over time, often linked to aging and repetitive joint use.
  • Rheumatoid Arthritis (RA): An autoimmune condition that leads to chronic inflammation in the shoulder joint, resulting in pain, swelling, and possible joint deformity.
  • Post-Traumatic Arthritis: Develops after an injury, such as a shoulder fracture or dislocation, which can accelerate cartilage degeneration.
  • Avascular Necrosis: A condition where the blood supply to the shoulder bone is disrupted, leading to bone and cartilage damage.
  • Infectious Arthritis: Caused by an infection in the shoulder joint, leading to inflammation, pain, and swelling.

Types of Shoulder Arthritis

  • Osteoarthritis (OA): A degenerative joint disease that results in cartilage breakdown, causing pain and stiffness, particularly in older adults.
  • Rheumatoid Arthritis (RA): An autoimmune disorder affecting the synovium of the shoulder joint, leading to inflammation, swelling, and potential deformity.
  • Post-Traumatic Arthritis: A type of arthritis that occurs following a significant shoulder injury or trauma, leading to joint deterioration over time.
  • Avascular Necrosis: This occurs when a lack of blood supply to the humeral head causes the bone to weaken and collapse, eventually leading to arthritis.
  • Infectious Arthritis: A rare but serious condition where bacteria or viruses infect the shoulder joint, leading to severe pain and inflammation.

Symptoms of Shoulder Arthritis

  • Pain: Pain in the shoulder, especially with movement, lifting objects, or at rest.
  • Stiffness: Reduced range of motion, making it difficult to lift the arm or reach overhead.
  • Swelling: Inflammation around the shoulder joint, often accompanied by discomfort.
  • Weakness: A sensation of instability or weakness in the shoulder, making daily activities challenging.
  • Crepitus: A grinding, clicking, or popping sensation in the shoulder joint during movement.

Shoulder arthritis can significantly impact the quality of life, but treatment options such as physical therapy, medications, corticosteroid injections, or in severe cases, shoulder replacement surgery, can help alleviate pain and improve function.

Shoulder Bursitis: Causes, Types, and Symptoms

Shoulder bursitis is a condition characterized by inflammation of the bursa, a small fluid-filled sac that cushions the shoulder joint. This inflammation can cause pain, swelling, and limited mobility, affecting daily activities like lifting, reaching, or even lying on the affected side.

Causes of Shoulder Bursitis

Shoulder bursitis can develop due to various factors, including:

  • Repetitive Movements & Overuse: Frequent overhead motions in sports (e.g., swimming, baseball) or work-related tasks (e.g., painting, lifting) can irritate the bursa.
  • Trauma & Injury: A direct blow to the shoulder, a fall, or sudden impact can lead to bursitis.
  • Poor Posture: Slouching or improper shoulder mechanics can put extra pressure on the bursa, leading to irritation.
  • Aging & Degeneration: The natural aging process can make the bursa more susceptible to inflammation and irritation.
  • Underlying Conditions: Conditions like rheumatoid arthritis, gout, or infections can contribute to bursitis.

Types of Shoulder Bursitis

  • Subacromial Bursitis: The most common form, occurring under the acromion (top part of the shoulder blade), often associated with rotator cuff injuries.
  • Chronic Bursitis: Long-term inflammation due to repeated irritation or an underlying condition like arthritis.
  • Traumatic Bursitis: Develops after a direct impact or injury to the shoulder, causing sudden swelling and pain.

Symptoms of Shoulder Bursitis

  • Pain: A dull, aching pain in the shoulder, especially when moving the arm overhead or to the side.
  • Swelling: Puffiness or localized inflammation around the affected area.
  • Tenderness: Pain when pressing on the shoulder or lying on the affected side.
  • Stiffness & Limited Motion: Difficulty lifting or rotating the arm due to discomfort.
  • Warmth & Redness: Possible signs of infection if the bursitis is septic.

Shoulder bursitis can interfere with daily activities, but treatment options such as rest, ice, physical therapy, anti-inflammatory medications, corticosteroid injections, or, in severe cases, surgery, can help reduce pain and restore shoulder function.

Rotator Cuff Injuries: Causes, Types, and Symptoms

Rotator cuff injuries occur when the muscles and tendons surrounding the shoulder joint become damaged or inflamed. These injuries can lead to pain, weakness, and limited shoulder mobility, affecting daily activities such as lifting, reaching, or sleeping on the affected side.

Causes of Rotator Cuff Injuries

Rotator cuff injuries can result from various factors, including:

  • Overuse & Repetitive Movements: Common in athletes and individuals with jobs that require frequent overhead motions (e.g., painters, carpenters).
  • Aging & Degeneration: Natural wear and tear over time can weaken the tendons, making them more prone to injury, especially in individuals over 40.
  • Trauma & Sudden Injury: A fall, heavy lifting, or direct impact to the shoulder can cause acute tears in the rotator cuff tendons.
  • Poor Posture: Incorrect posture, especially with prolonged forward shoulder positioning, can increase stress on the rotator cuff.

Types of Rotator Cuff Injuries

  • Tendonitis: Inflammation of the rotator cuff tendons due to overuse or strain, often causing pain and stiffness.
  • Partial Tear: A tear in the rotator cuff that does not completely sever the tendon, often causing pain with certain movements.
  • Full-Thickness Tear: A complete tear where the tendon detaches from the bone, significantly impacting shoulder function and strength.

Symptoms of Rotator Cuff Injuries

  • Pain: Shoulder pain, especially when lifting the arm, reaching behind the back, or lying on the affected side.
  • Weakness: Difficulty lifting or rotating the arm due to tendon damage.
  • Limited Range of Motion: Stiffness and difficulty in fully moving the shoulder.
  • Clicking or Popping Sounds: Sensation of popping or cracking when moving the arm.
  • Night Pain: Increased discomfort when resting or sleeping, particularly when lying on the injured shoulder.

Rotator cuff injuries can impact daily life, but treatment options such as physical therapy, medications, corticosteroid injections, or, in severe cases, surgery can help relieve pain and restore function.

AC Joint Injuries: Causes, Types, and Symptoms

Acromioclavicular (AC) joint injuries occur when the ligaments that connect the clavicle (collarbone) to the acromion (part of the shoulder blade) become damaged. These injuries can lead to pain, instability, and reduced shoulder function, affecting activities such as lifting, reaching, or carrying objects.

Causes of AC Joint Injuries

AC joint injuries can result from various factors, including:

  • Direct Trauma: A fall directly onto the shoulder or a direct blow (common in contact sports like football, hockey, or wrestling) can damage the AC joint.
  • Repetitive Stress & Overuse: Continuous overhead movements (e.g., weightlifting, throwing sports) can cause wear and tear on the AC joint.
  • Degenerative Arthritis: Over time, the AC joint can wear down due to aging or repetitive use, leading to joint pain and dysfunction.
  • Heavy Lifting: Carrying heavy loads, especially across the shoulders, can place excessive strain on the AC joint.

Types of AC Joint Injuries

  • AC Joint Sprain (Grade I): Mild ligament stretching or small tears, causing minor pain and swelling.
  • Partial AC Joint Separation (Grade II): A more significant tear in the AC ligaments, leading to moderate pain and a noticeable bump at the joint.
  • Complete AC Joint Separation (Grade III+): A full rupture of the ligaments, causing severe pain, a prominent deformity, and possible collarbone elevation.
  • AC Joint Osteoarthritis: Degenerative changes in the AC joint due to wear and tear, leading to chronic pain and stiffness.

Symptoms of AC Joint Injuries

  • Pain: Localized pain at the top of the shoulder, especially with movement or pressure.
  • Swelling & Bruising: Inflammation around the AC joint, sometimes with visible bruising.
  • Deformity or Bump: A noticeable elevation of the collarbone in more severe injuries.
  • Limited Shoulder Motion: Difficulty lifting the arm, particularly overhead or across the body.
  • Weakness & Instability: A feeling of weakness or instability in the shoulder when carrying objects.

AC joint injuries can impact shoulder function, but treatment options such as rest, ice, physical therapy, pain management, bracing, corticosteroid injections, or, in severe cases, surgery can help relieve pain and restore mobility.

Shoulder & Clavicle Fractures: Causes, Types, and Symptoms

Fractures in the shoulder or clavicle region occur when one of the bones in the shoulder complex—such as the clavicle (collarbone), scapula (shoulder blade), or humerus (upper arm bone)—breaks due to trauma. These fractures can cause significant pain, swelling, and limited arm movement, affecting daily activities like lifting, reaching, or even supporting body weight.

Causes of Shoulder & Clavicle Fractures

Fractures in this region can result from various factors, including:

  • Falls: Landing on an outstretched arm or directly on the shoulder can cause fractures, especially in the clavicle or humerus.
  • Direct Trauma: A strong impact, such as a car accident or sports collision, can break bones in the shoulder.
  • High-Energy Injuries: Severe accidents, such as motorcycle crashes, can lead to complex fractures, especially in the scapula.
  • Osteoporosis: Weak or brittle bones due to age-related bone loss can increase the risk of fractures with minor falls or impacts.

Types of Shoulder & Clavicle Fractures

  • Clavicle (Collarbone) Fracture: A break in the clavicle, often caused by falls or direct impacts, resulting in shoulder pain and a visible deformity.
  • Proximal Humerus Fracture: A fracture near the top of the upper arm bone, common in older adults with osteoporosis.
  • Scapula (Shoulder Blade) Fracture: Less common but serious, usually caused by high-impact trauma like car accidents.
  • Acromion Fracture: A break in the top part of the shoulder blade, affecting the function of the shoulder joint.

Symptoms of Shoulder & Clavicle Fractures

  • Severe Pain: Sharp pain, especially when moving the shoulder or arm.
  • Swelling & Bruising: Inflammation and discoloration around the fracture site.
  • Deformity or Bump: A visible abnormality in the collarbone or shoulder contour.
  • Limited Arm Mobility: Difficulty raising or moving the arm due to pain and instability.
  • Grinding or Popping Sensation: A feeling of bone fragments moving when attempting to use the shoulder.

Shoulder and clavicle fractures can significantly impact daily function, but treatment options such as immobilization with a sling, pain management, physical therapy, or, in severe cases, surgery can help restore movement and stability.

Shoulder Instability: Causes, Types, and Symptoms

Shoulder instability occurs when the shoulder joint is unable to maintain its proper position, leading to excessive movement, weakness, or dislocation. This condition can cause pain, reduced function, and an increased risk of recurrent injuries, affecting activities like lifting, throwing, or even sleeping on the affected side.

Causes of Shoulder Instability

Shoulder instability can result from various factors, including:

  • Trauma & Dislocation: A previous shoulder dislocation or injury can stretch or tear the ligaments, making the joint more prone to instability.
  • Repetitive Overuse: Frequent overhead motions in sports (e.g., swimming, baseball, volleyball) or work-related tasks can weaken the stabilizing structures of the shoulder.
  • Ligament Laxity (Loose Ligaments): Some individuals have naturally loose ligaments, making them more prone to shoulder instability, especially in both shoulders.
  • Weak Shoulder Muscles: Poor muscle strength around the shoulder joint can contribute to instability, as the muscles play a key role in keeping the joint in place.

Types of Shoulder Instability

  • Traumatic Shoulder Instability: Occurs after a dislocation or significant injury that damages the ligaments, leading to chronic instability.
  • Atraumatic Shoulder Instability: Develops gradually due to repetitive strain, poor muscle control, or naturally loose ligaments.
  • Multidirectional Instability (MDI): Instability in multiple directions (front, back, or downward), common in individuals with hypermobility or weak shoulder muscles.
  • Anterior Instability: The most common form, where the shoulder moves too far forward and can lead to dislocations.
  • Posterior Instability: Less common, where the shoulder shifts backward, often due to repetitive pushing or weightlifting activities.

Symptoms of Shoulder Instability

  • Pain: Discomfort in the shoulder, especially with movement or overhead activities.
  • Weakness & Fatigue: A feeling of weakness or heaviness in the arm, particularly after activity.
  • Looseness or Shifting Sensation: A feeling that the shoulder might “slip out” or move excessively.
  • Frequent Dislocations or Subluxations: The shoulder fully or partially dislocates, causing significant pain and dysfunction.
  • Clicking or Popping: Unusual sounds or sensations when moving the shoulder.

Shoulder instability can interfere with daily function, but treatment options such as physical therapy, strengthening exercises, activity modification, bracing, or, in severe cases, surgery can help restore stability and prevent further dislocations.

Proximal Biceps Tendon Injuries: Causes, Types, and Symptoms

Long head biceps tendon injuries occur when the tendon connecting the biceps muscle to the shoulder joint becomes inflamed, frayed, or torn. These injuries can lead to pain, weakness, and reduced arm function, affecting activities like lifting, reaching, or rotating the arm.

Causes of Long Head Biceps Tendon Injuries

Long head biceps tendon injuries can result from various factors, including:

  • Overuse & Repetitive Motion: Frequent overhead activities (e.g., swimming, baseball, weightlifting) can lead to wear and tear on the tendon.
  • Aging & Degeneration: As people age, the tendon naturally weakens, making it more susceptible to fraying or tearing.
  • Trauma & Injury: A sudden fall, heavy lifting, or direct impact to the shoulder can cause acute damage to the tendon.
  • Shoulder Instability & Rotator Cuff Injuries: Conditions like rotator cuff tears or shoulder impingement can contribute to biceps tendon damage.

Types of Long Head Biceps Tendon Injuries

  • Biceps Tendinitis: Inflammation of the tendon, leading to pain and stiffness in the front of the shoulder.
  • Biceps Tendinosis: Chronic degeneration of the tendon due to overuse, often without significant inflammation.
  • Partial Tear: A partial rupture of the tendon, causing pain and weakness with arm movement.
  • Complete Tear (Biceps Tendon Rupture): The tendon fully detaches from the shoulder, leading to a “Popeye deformity” where the biceps muscle bunches up.

Symptoms of Long Head Biceps Tendon Injuries

  • Pain: Deep, aching pain in the front of the shoulder, especially with overhead or lifting movements.
  • Weakness: Reduced strength when bending the elbow or rotating the forearm.
  • Clicking or Popping Sounds: Sensations of snapping or popping in the shoulder with movement.
  • Tenderness: Sensitivity to touch along the front of the shoulder.
  • Muscle Deformity (in severe cases): A bulging appearance in the upper arm due to tendon rupture.

Long head biceps tendon injuries can affect daily activities, but treatment options such as rest, physical therapy, anti-inflammatory medications, corticosteroid injections, or, in severe cases, surgical repair or tenodesis, can help restore function and reduce pain.

SLAP Tears: Causes, Types, and Symptoms

A SLAP (Superior Labrum Anterior to Posterior) tear is an injury to the labrum, the ring of cartilage surrounding the shoulder socket. This injury can lead to pain, instability, and reduced shoulder function, affecting activities like throwing, lifting, or reaching overhead.

Causes of SLAP Tears

SLAP tears can result from various factors, including:

  • Repetitive Overhead Movements: Common in athletes such as baseball pitchers, swimmers, and weightlifters due to repeated stress on the shoulder.
  • Trauma & Falls: Falling onto an outstretched arm or experiencing a direct impact to the shoulder can cause a SLAP tear.
  • Heavy Lifting: Sudden or excessive force while lifting, especially overhead, can strain and tear the labrum.
  • Degeneration & Aging: Over time, the labrum naturally weakens, making it more susceptible to tears, particularly in individuals over 40.

Types of SLAP Tears

  • Type I: Degenerative fraying of the labrum, but no significant detachment.
  • Type II: The most common type, where the labrum and biceps tendon detach from the socket.
  • Type III: A “bucket-handle” tear, where a portion of the labrum is torn but remains attached.
  • Type IV: A severe tear that extends into the biceps tendon, potentially requiring surgical repair.

Symptoms of SLAP Tears

  • Pain: Deep shoulder pain, especially with overhead or behind-the-back movements.
  • Clicking or Popping Sounds: Sensations of catching, locking, or grinding in the shoulder.
  • Weakness: Decreased strength in the shoulder, particularly with lifting or throwing.
  • Instability: A feeling of looseness or the shoulder “giving out.”
  • Reduced Range of Motion: Difficulty reaching overhead or rotating the arm.

SLAP tears can impact shoulder function, but treatment options such as rest, physical therapy, anti-inflammatory medications, corticosteroid injections, or, in severe cases, arthroscopic surgery can help relieve pain and restore stability.

Shoulder Impingement: Causes, Types, and Symptoms

Shoulder impingement is a condition where the tendons of the rotator cuff become irritated or compressed, typically beneath the acromion (the bony part of the shoulder blade). This can lead to pain, weakness, and limited range of motion, particularly during overhead activities.

Causes of Shoulder Impingement

Shoulder impingement can result from various factors, including:

  • Repetitive Overhead Movements: Common in athletes such as swimmers, baseball players, or weightlifters, who stress the shoulder with frequent overhead motions.
  • Poor Posture: Prolonged poor posture can alter the mechanics of the shoulder, contributing to impingement.
  • Aging & Wear: As individuals age, wear and tear on the rotator cuff tendons can lead to narrowing of the subacromial space and increased friction.
  • Anatomical Factors: Structural issues, such as a hooked acromion or an abnormally shaped acromion, can reduce the space available for the tendons.

Types of Shoulder Impingement

  • Primary Impingement: Caused by structural issues, such as bone spurs or a hooked acromion that reduce the subacromial space and irritate the tendons.
  • Secondary Impingement: Caused by poor shoulder mechanics, such as muscle weakness or instability, that leads to abnormal movement patterns, causing tendons to become pinched.
  • Internal Impingement: Often seen in athletes, where the rotator cuff tendons rub against the posterior aspect of the shoulder socket during overhead activities.

Symptoms of Shoulder Impingement

  • Pain: Pain, particularly when lifting the arm overhead or reaching behind the back.
  • Weakness: Decreased strength in the shoulder, especially when trying to lift or move the arm overhead.
  • Tenderness: Pain and tenderness on the outer part of the shoulder.
  • Limited Range of Motion: Difficulty lifting the arm or rotating the shoulder.
  • Pain at Night: Worsening pain when lying on the affected side, especially during sleep.

Shoulder impingement can significantly affect daily activities and athletic performance, but treatment options such as rest, physical therapy, anti-inflammatory medications, and, in some cases, surgery can help relieve symptoms and restore function.

Injuries to the Overhead Athlete: Causes, Types, and Symptoms

Overhead athletes, such as baseball players, swimmers, tennis players, and volleyball players, are particularly prone to injuries due to the repetitive and high-stress movements involved in their sports. These injuries often affect the shoulder, elbow, and wrist, as these joints are heavily involved in overhead motions.

Causes of Injuries to the Overhead Athlete

Injuries in overhead athletes can result from several factors, including:

  • Repetitive Overhead Motion: Repeated throwing, swimming strokes, or hitting motions create significant stress on the shoulder and elbow joints.
  • Poor Mechanics: Incorrect form or inefficient movement patterns increase the risk of injury, especially with improper technique in throwing or swimming strokes.
  • Overuse: Playing a sport excessively without sufficient rest can lead to overuse injuries, particularly in young athletes with developing muscles and joints.
  • Imbalance in Muscle Strength: Weakness or imbalances in the rotator cuff, scapular stabilizers, or the forearm muscles can place added stress on the joints.
  • Aging: As athletes age, the tendons and ligaments become less flexible and more prone to wear and tear, increasing the risk of injury.

Common Types of Injuries to the Overhead Athlete

  • Rotator Cuff Tendonitis: Inflammation of the rotator cuff tendons, often caused by repetitive overhead movements.
  • Labral Tears: Tears in the shoulder labrum, such as SLAP tears, can occur from repetitive overhead stress or trauma.
  • Shoulder Impingement: Compression of the rotator cuff tendons beneath the acromion, leading to pain and limited range of motion.
  • Shoulder Instability: A feeling of looseness in the shoulder, often due to overstretching of the joint capsule or ligaments.
  • Ulnar Collateral Ligament (UCL) Injury: A common injury in throwing athletes, especially baseball pitchers, where the UCL in the elbow is overstretched or torn.
  • Tennis Elbow (Lateral Epicondylitis): Inflammation of the tendons on the outside of the elbow due to repetitive arm motions.
  • Biceps Tendonitis: Inflammation of the biceps tendon, often linked to repetitive overhead lifting or throwing motions.

Symptoms of Injuries to the Overhead Athlete

  • Pain: Pain, especially when performing overhead movements or throwing motions. This can vary from a dull ache to sharp pain.
  • Weakness: Decreased strength in the shoulder, elbow, or wrist, particularly when trying to lift or throw.
  • Instability: A feeling that the joint is loose or may “give out,” especially with shoulder instability.
  • Swelling: Swelling in the shoulder or elbow joint, often associated with tendonitis or ligament injuries.
  • Limited Range of Motion: Difficulty with full overhead motion, particularly in the shoulder or elbow.
  • Clicking or Popping: A sensation of catching, clicking, or popping in the joint, which may be associated with labral tears or shoulder instability.

Treatment Options for Injuries to the Overhead Athlete

  1. Conservative Treatment:
    • Rest: Avoiding overhead activities to allow for healing.
    • Ice Therapy: Applying ice to reduce swelling and pain.
    • Physical Therapy: Focused on strengthening the rotator cuff, scapular stabilizers, and other muscles to improve shoulder mechanics and prevent re-injury.
    • Anti-Inflammatory Medications: NSAIDs to reduce pain and inflammation.
    • Corticosteroid Injections: For more persistent pain and inflammation.
  2. Surgical Treatment:
    • Rotator Cuff Repair: If tendon tears occur, surgery may be required to reattach the tendons.
    • Labral Repair: In cases of labral tears (e.g., SLAP tears), arthroscopic surgery may be needed to repair the labrum.
    • Tommy John Surgery (UCL Reconstruction): For athletes with UCL tears, especially pitchers, this surgery reconstructs the ligament to restore elbow stability.

Injuries to the overhead athlete can severely impact performance and daily activities, but with early diagnosis and appropriate treatment, athletes can return to play with minimized risk of re-injury. Proper training, mechanics, and rest are key components of injury prevention.