Jessica J. Leeman, DVM (Surgery Resident)
Seattle Veterinary Specialists
The canine shoulder joint is composed of the glenoid cavity of the scapula and the humeral head. There are many soft tissue structures that surround the joint and aid in its stability. The medial and lateral glenohumeral ligaments and associated joint capsule provide its static stability, while multiple surrounding muscles provide its dynamic stability. These muscles include the supraspinatus, infraspinatus, teres minor, subscapularis, and the biceps brachii muscles.
The shoulder joint’s primary motions are flexion and extension. Other joint motions include abduction, adduction, internal/external rotation, cranial, caudal, medial, and lateral translation, and the motion of the scapula in relation to the body wall. Reported normal angles of motion of the shoulder joint are listed below. It is important to note that these angles may differ by breed.
The underlying etiology of shoulder tendinopathies is largely unknown, however the main theory is related to repetitive stress or injury in highly active dogs. Repetitive stress induces damage to the tendons and ligaments which may include partial tears, mineralization, chronic tenosynovitis, peritendinous adhesions, and contractures. Hypoxia has also been proposed as a contributing factor in tendon injuries, as tendons and ligaments tend to have difficulty healing due to their relatively avascularity. In cases other than inflammatory bicipital tenosynovitis, inflammation has not been shown to play a role in shoulder tendinopathies.
mineralization, chronic tenosynovitis, peritendinous adhesions, and contractures. Hypoxia has also been proposed as a contributing factor in tendon injuries, as tendons and ligaments tend to have difficulty healing due to their relatively avascularity. In cases other than inflammatory bicipital tenosynovitis, inflammation has not been shown to play a role in shoulder tendinopathies.
Dogs with shoulder tendinopathies are often presented to their veterinarians with the presenting complaint of chronic, intermittent, unilateral or bilateral forelimb lameness that usually worsens with exercise. Some dogs may be completely non-weightbearing if the tendinopathy is severe. These dogs are often working or agility dogs who have high activity levels.
The physical exam is the most important part of evaluating a dog with forelimb lameness. Thorough orthopedic and neurologic evaluations are key in diagnosing tendinous abnormalities. Gait evaluation, posture, and palpation are the three parts to a good orthopedic evaluation. Gait evaluation usually reveals some degree of lameness, however there are cases were the patients are completely sound. Little assistance is needed when transitioning between standing or sitting/lying down. Dogs with tendiopathies usually shift their weight to the contralateral sound forelimb for relief. Palpation of the affected joint may reveal decreased range of motion with or without pain, trigger points of surrounding musculature, and discomfort when manual pressure is directly applied to the affected tendon. The best way to feel the biceps tendon is palpation of the tendon in the bicipital groove with the shoulder joint in flexion. You may also apply manual pressure to the nearby insertion of the supraspinatus tendon during this manipulation as well. The insertion of the supraspinatus tendon is directly on the craniomedial aspect of the humeral head. Joint angles may be measured via goniometry during the orthopedic exam as an objective measurement that may be useful in monitoring improvement during the healing phase. A simultaneous neurologic examination is recommended to help rule in/out cervical/thoracic lesions, as it can sometimes be difficult in determine the primary body system effected. The orthopedic and neurologic exams may be helpful in determining the best diagnostic approach.
Further diagnostics are usually recommended in any dog with forelimb lameness. It is important to rule in/out other causes of the lameness if the owner is willing and able to do so. Forelimb lameness can be broken down into three main categories: osseus, soft tissue (tendinous/ligamentous), or neurologic etiologies. The first diagnostic step is usually plain radiographs. This imaging modality is a great way to rule out osseous causes of the lameness, primarily looking for primary bone tumors in older patients or OCD lesions in young dogs. Subtle changes on radiographs can be indicative of a shoulder tendionpathy and include osteophytosis of the glenohumeral joint and/or within the bicipital groove. Additionally, mineralization within the tendons can sometimes be visualized as well.
Further imaging of the glenohumeral joint includes the use of ultrasound and/or MRI. Arthroscopy has also been used to evaluate the shoulder joint for diagnostic purposes as well. Ultrasonography is a non-invasive and relatively inexpensive way to evaluate the majority of the shoulder joint. Additionally, patients do not need to be anesthetized and rarely require sedation. This can also be performed on an outpatient basis and allows serial monitoring during the healing process. Ultrasound is especially useful when there is a high suspicion that the supraspinatus and biceps tendon are thought to be responsible for the lameness. These structures are easily identified ultrasonographically and this modality has a high sensitivity (ultrasonographer dependent). The limitation of ultrasound is the inability to evaluate the medial compartment of the joint and some lesions may be missed (low specificity). Significant findings during an ultrasound of the shoulder include tears of the affected tendon fibers, excessive effusion around the biceps tendon in bicipital tenosynovitis, sclerosis of the bicipital groove, calcification of the tendons, and impingement of the biceps tendon by the supraspinatus tendon. Additionally, osteophytosis consistent with osteoarthrosis can sometimes be visualized during ultrasound evaluation as well. MRI is the gold standard when evaluating the shoulder joint in humans due to its high sensitivity and specificity. Similarly, MRI is becoming the gold standard in veterinary medicine given the progressive availability of this advance imaging modality. An MRI is the diagnostic tool that will give us the most information about our patient. Not only does it allow evaluation of the lateral compartment of the shoulder joint, it allows evaluation of the medial compartment and cervical/thoracic spine and associated peripheral nerves. The downside of the imaging modality is that it requires anesthesia and can be cost prohibitive for some owners. Similar significant findings can be seen on MRI as with ultrasound when evaluating the biceps and supraspinatus tendons. Direct visualization of the shoulder joint via arthroscopy is also a diagnostic modality that is commonly performed. The benefit of arthroscopy includes evaluation of the majority of the intra-articular structures, such as the glenohumeral ligaments, caudal joint, articular surface, and biceps tendon. It does not allow for direct visualization of the supraspinatus tendon, however a tendinopathy of this muscle can be assumed if there is impingement or displacement of the biceps tendon within the bicipital groove. If a significant biceps tendinopathy is visualized during arthroscopy, a therapeutic biceps tendon release can be performed at the same time.
Therapy for shoulder tendinopathies depends on three main factors: cost, invasiveness, and expected case outcome. An in-depth conversation is had with the owner to determine the best therapeutic road based on the individual patient and injury. Overall, therapy is directed at keeping our patients comfortable, while improving lameness and encouraging overall joint health. In some cases, our goal may be directed at achieving tissue regeneration of the affected tendon.
Analgesia is typically provided by NSAIDs, tramadol, methocarbamol, and in some instances intra-articular depomedrol. These medications are typically prescribed in combination with one another, with the exception of the use of NSAIDs and intra-articular depomedrol. If depomedrol is used intra-articularly, we recommend discontinuing the use of NSAIDs for 6 weeks due to some systemic absorption of the depomedrol from the joint. Providing joint health consists of the use of pharmaceuticals and neutraceuticals in addition to physical activity in the form of physical rehabilitation. Adequan, Dasuquin, and omega-3 fatty acids are the “joint supplements” we recommend for just about every patient who has some form of osteoarthrosis or who we think will develop it in the future. The supplements have been shown to help improve mobility with evidence based medicine to support them. A thorough overview on the role of rehabilitation in the management of shoulder tendinopathies would require a separate discussion, but it should be known that it plays a large role in any therapy chosen for the management of these injuries.
In addition to the above recommendations for medical management of shoulder tendinopathies, other non-surgical therapies under the umbrella term “regenerative medicine” may be helpful and include the use of LASER, extra-corporeal shockwave therapy (ESWT), stem cell therapy, and platelet-rich plasma. Currently these therapies have very little evidence to support their use in canine shoulder tendinopathies, however information from human studies and studies on similar tissue types is available and have favorable evidence to support their use in these types of injuries. Nevertheless, the risks associated with these therapies have been shown to have little, if any, side effects and most likely will not worsen the injury.
LASER and ESWT are the least invasive therapies of its kind. LASER, an acronym for “Light Amplification Stimulated by the Emission of Radiation,” has been shown to aid in healing of ligamentous/tendinous injuries in mice and may provide pain relief. In the most basic description LASER works by stimulating the mitochondria of cells to increase the production of ATP, which is necessary for cell metabolism and growth. The mechanism of action by which LASER provides pain relief is less clear but may be related to the blockage of pain transmission to the central nervous system. LASER therapy does not require sedation or anesthesia and is relatively inexpensive ($45/session). We typically recommend 2-3x weekly sessions for 4 weeks. If there is minimal or no improvement other therapies should be considered. ESWT is the use of high energy ultrasound waves, approximately 1000x stronger than a typical abdominal ultrasound. The ultrasound probe emits a mechanical force that is transmitted through skin to the diseased tissue. On the cellular level it induces growth factors to the site of injury and promotes tissue regeneration and healing, which may be especially beneficial in rather avascular tissues such as ligaments and tendons. This therapy is performed under heavy sedation due to discomfort of the pulses. We typically recommend 3 sessions spaced 3 weeks apart and the cost of this therapy is approximately $400/session. Similarly to LASER therapy, ESWT is commonly performed in conjunction a rehabilitation plan. NSAIDs are typically discontinued for 3-5 days following therapy as they can counteract that influx of growth factors to the affected tissue. Analgesia, typically tramadol, is prescribed during this period due to discomfort associated with the pulsations. LASER and ESWT are usually recommended in cases of mild-moderate shoulder tendinopathies or if surgery is not an option for severe cases. Stem cell therapy and platelet rich plasma are not currently performed at our practice for management of shoulder tendinopathies, however there are several ongoing studies that may support their use in the future.
Surgical management of shoulder tendinopathies is recommended in moderate-severe cases or when non-surgical management has failed. The surgery is essentially aimed at “cutting the affected tendon.” In the case of supraspinatus tendinopathy, a partial excision of the insertion of the tendon is excised via arthrotomy. This procedure is aimed at excising the portion of the supraspinatus tendon that is primarily causing the patient discomfort and/or releases the impingement it is causing secondarily to the underlying biceps tendon. During this procedure any adhesions are freed to allow normal motion of the biceps tendon within the bicipital groove. Additionally, an injection of depomedrol can be performed at the same time if the patient has evidence of bicipital tenosynovitis. In cases where the biceps tendon is primarily affected, a biceps tendon release or tenodesis may be performed. There have been no studies indicating a difference in outcome with either technique and the procedure chosen is usually dependent on surgeon preference. Additionally if the approach to the biceps tendon is done arthroscopically, a biceps tendon release without tenodesis is usually performed. Similarly, an intra-articular injection of depo-medrol can be performed in cases of bicipital tenosynovitis. The recovery period is approximately 6 weeks. During this time, physical rehabilitation recommendations are made and patients are encouraged to gradually increase activity over this time period.
Long-term outcome varies with severity of the tendinopathy and the therapeutic approach. In cases of mild shoulder tendinopathies the prognosis is generally good (~80%) with non-surgical management (especially with ESWT). In cases where non-surgical management has failed or in cases with severe lesions, prognosis is still generally good-excellent when surgery is performed (~90%). The best outcome can be expected when a multi-modal approach is used.
Canine shoulder tendinopathies are a relatively common cause of forelimb lameness and can be challenging to diagnose on physical exam alone. Advanced imaging modalities are useful diagnostics that often result in an accurate diagnosis which is important for therapy. There are numerous treatment options that are available and recommended based on the individual patient and the severity of the injury. A multi-modal approach to management of shoulder tendinopathies is often recommended. Short and long-term prognoses are usually good-excellent in the majority of cases.