Overview
Shoulder tendon injuries are a common cause of canine forelimb lameness. The supraspinatus and biceps tendons are the most frequently impacted. With repetitive stress or overuse, these tendons can experience inflammation, degeneration, and/or tearing of their fibers. These weakened structures are prone to continued injury and development of “core” lesions. Over time, the tendon fiber pattern is disrupted, and scar tissue develops that can compress adjacent tendons. Chronic cases may show tendon mineralization or bony remodeling at insertion points. While these injuries can occur in companion animals, they are more common in working and agility dogs. Larger dogs, such as Labrador Retrievers and Rottweilers, seem to be predisposed.
The supraspinatus muscle and associated tendon are located at the front of the shoulder joint and function to extend the shoulder joint and advance the limb. Supraspinatus changes can cause primary discomfort and can also compress the adjacent biceps tendon, causing secondary bicipital tenosynovitis (inflammation).
Alternatively, the biceps tendon can be injured primarily without any supraspinatus involvement. The biceps tendon crosses the front of the shoulder joint, acting as a shoulder stabilizer and allowing the associated muscle to flex the elbow.
Clinical Signs
- Intermittent or persistent forelimb lameness, often with a shortened stride
- A “warm-up” lameness that improves during activity, then worsens afterward
- Pain on direct palpation of the tendon(s)
- Reduced shoulder extension
- Muscle atrophy with chronic cases
Diagnosis
Soft tissue injuries (tendons, muscles, and ligaments) of the shoulders are frequently missed or misdiagnosed causes of lameness in dogs. These injuries create a cycle where dogs improve with rest but become lame again with exercise due to progressive scarring that further weakens the structures. Additionally, osteoarthritis can form over time with continued instability. Early diagnosis is crucial, as the longer the condition persists, the less likely a full recovery becomes.
Diagnosis begins with a comprehensive orthopedic examination including shoulder range of motion, discomfort on direct palpation, biceps test (flexion of shoulder with extended elbow), and comparison with the other forelimb. Scar tissue can sometimes be visualized as a rapidly growing “supraspinatus bulge.” In chronic cases, radiographs (x-rays) can see calcifications within the supraspinatus or biceps tendon (about 25% of all cases). In acute cases, radiographs may be unable to visualize soft tissue specifics, but they are still helpful to rule out other conditions of the shoulder that can have similar clinical signs. Next steps include non-invasive advanced imaging (musculoskeletal ultrasound or MRI) or arthroscopy (both diagnostic and therapeutic).
Treatment Options
Conservative Management consists of rest/ activity restriction, rehabilitation therapy, and medications. Rehabilitation is essential for recovery and includes controlled range-of-motion maneuvers, proprioceptive training, strengthening exercises, and therapeutic modalities such as shockwave.
Regenerative medicine can be pursued in many cases and includes the injection of PRP into the tendon lesions or the joint. Steroid injections into the shoulder joint can sometimes be employed but are not recommended as a long-term treatment method.
Surgery is indicated for severe or refractory cases. Most commonly, arthroscopic release of the biceps tendon is performed.
Recovery and Prognosis
Recovery is slow, and unlike bone fractures, tendons often never return to full strength after injury, making early intervention critical for better outcomes. Complete recovery typically requires 3-12 months. A gradual rehabilitation protocol is essential for improved outcomes. Conservative management is typically successful in 60% of supraspinatus cases and 75+% of biceps cases. Surgery is reported to be successful in 90% of biceps cases. With either condition, lifelong management may be necessary, particularly in working or athletic dogs.
Prevention
While injuries can never be eliminated entirely, here are some steps to minimize the chances of shoulder injuries in your pet:
- Proper conditioning before intense activity
- Balanced strengthening of shoulder muscle groups
- Appropriate warm-up before exercise
- Avoiding repetitive high-impact activities in predisposed dogs
- Regular preventative rehabilitation for athletic dogs