Muscular Trauma in Dogs and Cats

Infraspinatus contracture is a uni- or bilateral fibrotic myopathy of the infraspinatus muscle that is usually secondary to trauma in hunting or working dogs. Initial clinical signs include an acute lameness, pain, and swelling in the shoulder region. The lameness subsides, but a gait abnormality develops 2–4 weeks after injury as muscle fibrosis and contracture progress. Clinical signs include a characteristic adduction of the elbow, abduction of the foreleg, and external rotation of the carpus and paw. The limb is circumducted with each stride of the leg. Palpation of the shoulders reveals outward rotation of the humerus as the elbow is flexed. Treatment consists of resection of the fibrous musculotendinous portion of the muscle, including tenotomy of the tendon of insertion. Limb and joint functions are immediately improved, and prognosis for full recovery is excellent.

This inflammation of the biceps brachii tendon of origin and associated synovial sheath can be uni- or bilateral. It usually affects mature, large dogs. The mechanism of injury can be direct, indirect, overuse, or migration of osteochondral fragments (“joint mice”) from humeral osteochondrosis lesions.

Clinical signs include a progressive or chronic, intermittent lameness that worsens after exercise and improves with rest. The range of motion of the shoulder joint is reduced, and atrophy of the shoulder muscles may be apparent. Acute pain can be elicited by applying digital pressure to the biceps tendon during flexion and extension of the shoulder joint.

Diagnosis can be confirmed by ultrasonography or arthroscopy of the damaged tendon. Radiography can reveal dystrophic calcification of the tendon, osteophytes in the intertubercular groove, or mineralized fragments within the tendon sheath. Contrast arthrography may demonstrate filling defects and irregularities of the synovial sheath. Arthrocentesis may be inconclusive. Diagnosis can also be made by exploration of the tendon and associated sheath.

Acute, mild cases can be treated with rest and oral NSAIDs and opioids. Acute, severe cases can be treated with intralesional injections of methylprednisolone acetate (20–40 mg) and rest. Chronic cases refractory to multiple corticosteroid injections or cases involving identifiable tendon defects or tears, or “joint mice,” are treated by tenodesis (resection and attachment of the tendon to the proximal humerus) and osteochondral fragment removal. Arthroscopic-guided tendon resection has also been described. Prognosis for recovery is good.

This serious fibrosis and contracture of the quadriceps muscles develops secondary to distal femoral fractures, inadequate surgical repair, and excessive dissection in young dogs. Adhesions develop between the bone, periosteal tissue, and quadriceps muscles, which lead to limb extension, disuse, osteoporosis, degenerative joint disease, and bone and joint deformations. Clinical signs include hyperextension and cranial displacement of the affected limb. Surgery is usually required to resect fibrous tissues and increase motion of the stifle joint. Bone and soft-tissue reconstructions along with postoperative flexion bandages and physical therapy are required to recover limb function. Prognosis is guarded. Prevention of the condition by accurate, biologic stable repairs of bone fractures is preferred.

This acute, traumatic injury to the common calcaneal tendon (gastrocnemius, superficial digital flexor, biceps femoris, semitendinosus, and gracilis muscle tendons) is seen primarily in mature working and athletic dogs. The common tendon can be ruptured or avulsed from the tuber calcanei of the talus. Ruptures may be partial or complete, and the gastrocnemius tendon component is most frequently affected.

Clinical signs include a severe nonweight-bearing lameness, tarsal hyperflexion, and a plantigrade stance. Palpation reveals swelling, pain, and torn or fibrotic tendon ends. Radiography may reveal avulsed bone fragments.

Treatment is by surgical repair of torn ends and reattachment of tendinous tissue to the tuber calcanei. External splints or fixators should be used to protect the repair for 4 weeks. Prognosis is variable and based on chronicity of the injury, success of the surgery, and expected performance of the dog.

Trauma to the iliopsoas muscle or tendon of insertion can cause an acute or chronic lameness in active dogs. Physical examination reveals focal pain at the proximal medial aspect of the thigh (attachment of tendon to the lesser trochanter), especially during simultaneous hip joint extension and internal rotation. Ultrasonography reveals disruption of muscle fibers, and radiography may reveal dystrophic calcifications at the region of tendon insertion. Treatment with rest and NSAIDs is helpful.

• Also see pet health content regarding exertional myopathy in dogs.