Shoulder Joint Ligament and Tendon Conditions in Dogs

Bicipital Tenosynovitis, Brachii Muscle Rupture, and Supraspinatus Avulsion in Dogs

The shoulder joint is a “ball-and-socket” joint. In four legged animals it is made up of the scapula/shoulder blade bones, and the humerus/upper bone of the front leg. These bones are supported by ligaments and tendons. A ligament is a band of connective or fibrous tissue that connects two bones or cartilage at a joint, and a tendon is a band of connective or fibrous tissue that connects a muscle to a bone.

Shoulder-joint ligament and tendon conditions make up the majority of causes for lameness in the canine shoulder joint, excluding osteochondritis dissecans (a condition characterized by abnormal development of bone and cartilage, leading to a flap of cartilage within the joint). It is a disease that occurs in medium to large-breed dogs when they become skeletally mature, around one year of age or older. The average age for development of this condition is between 3 to 7 years of age.

Symptoms and Types

• Symptoms will depend on the severity and long-term nature of the disease
• A decrease in muscle mass is a consistent finding for all conditions
• Bicipital tenosynovitis (an inflammation of the tendon and surrounding sheath of the biceps tendon – at the front of the shoulder blade)
  • Onset is usually subtle
  • Often of several months’ duration
  • Trauma to the limb or shoulder may be the inciting cause
  • Subtle, intermittent lameness that worsens with exercise
  • Short and limited swing-phase of gait owing to pain on extension and flexion of the shoulder
  • Pain inconsistently demonstrated on manipulation of shoulder
• Rupture of the tendon of the biceps brachii muscle (upper limb)
  • Signs similar to bicipital tenosynovitis
  • May have sudden (acute) onset due to a known traumatic event
  • Usually subtle, long-term (chronic) lameness that worsens with exercise
  • Mineralization of the tendon of the supraspinatus (shoulder joint) muscle — onset is usually subtle

Long-term (chronic) lameness that worsens with activity

• Forcible separation (known as an avulsion) or fracture of the tendon of the supraspinatus muscle (tendon that connects the scapula/bone of the shoulder blade with the humerus/bone of the upper limb)
  • Signs are similar to mineralization of the supraspinatus tendon.
  • Deterioration and scarring (known as fibrotic contracture) of the shoulder muscle — usually sudden (acute) onset, occurring during a period of intense outdoor exercise (such as hunting).
  • Shoulder lameness and tenderness gradually disappears within two weeks
  • Left untreated, condition results in long-term (chronic), persistent lameness, usually taking place 3 to 4 weeks later; may not be particularly painful to the dog
  • Decrease in muscle mass of the infraspinatus muscle (muscle atrophy)
  • When patient is walking, lower limb swings in an arc away from the body, as the paw is advanced

Causes

• Indirect or direct trauma is a likely culprit
• Repetitive strain injury (indirect trauma) is the most common cause
• Overexertion and/or fatigue
• Poor conditioning before performing athletic activities (i.e., lack of previous exercise, overweight, or inappropriate preparation)

Diagnosis

X-rays will be needed to determine what is wrong with the shoulder. Ultrasound and magnetic resonance imaging (MRI) may help identify muscle injuries, bicipital tenosynovitis, and rupture of the biceps tendon. It is also useful for determining the location of calcium densities near the intertubercular groove, where the long head of the biceps meets the upper part of the humerus. A joint tap and analysis of fluid from the joint will help identify intra-articular (within the joint) disease. An arthroscopic exploration of the shoulder joint will help diagnose bicipital tenosynovitis, rupture of the biceps tendon, and will confirm or rule out intra-articular disease. This method of diagnostics is performed using an arthroscope, a specially equipped endoscope, which is a tubular device that can be inserted into the joint in order to remove fluid, tissue, or other material for analysis. It includes a camera for visual inspection, and can be outfitted with tools for removal of samples, and for treating the cavity or internal structure.