A hygroma is defined as a "cyst containing serous (clear yellow) fluid". Hygroma at the point of the elbow appears as a nodular soft tissue swelling located over the point of the elbow which is known as the olecranon tuberosity. There are several causes of hygromas in this location but all involve recurring trauma. Perhaps the most common cause it the hoof hitting the point of the elbow while the horse is lying down with his legs folded up under him. Prolonged recumbency, shoes expecially those with long heels or heel caulks predispose to irritation. Hygroma also occurs in high-gaited breeds that traumatize the elbow with the hoof. The condition can occur on just one or both front limbs. This article discusses the appearance, diagnosis, treatment, prevention, and prognosis of this condition.

At first injury may result in edema with a diffuse swelling under the skin but with recurrent injury the fluid can become surrounded by a firm fibrous capsule that develops a synovial lining. This could be called a traumatic bursitis. There will be various amounts of granulation tissue and scar around the capsule. Often a bursitis of the triceps brachii muscle bursa occurs with recurring injury. Once the condition becomes chronic and a bursa develops treatment is difficult and often unrewarding so during the first few episodes is the best time to institute preventive measures, see below.

Lameness is not generally seen except right after injury or if the lesion becomes infected. With infection the swelling will open and drain puss and exuberant granulation tissue formation are characteristic.