Ashley is a 100 pound, 4 year old Yellow Lab who presented to us with a sudden onset of lameness in the right shoulder. According to her owner, there was no distinctive incident which brought on the lameness. There had been no recent travel history,and there were no other pets in the yard with Ashley and she had no previous history of lameness in this or any other leg. Ashley’s owner was unable to find the source of the pain in the leg, but thought that it might be in the foot.
On physical exam, Ashley was in good spirits, bouncing around the exam room as most labs do. She had no other physical problems except that she was about 10 pounds too heavy (another common problem among labs). She was obviously lame on her right front limb. When examining a pet for lameness, we typically place a muzzle on the pet to prevent accidental bites when the sore point is manipulated. Once the pet is safely restrained, we examine each joint of the foot for pain or swelling. We check the pads and toes for foreign bodies (such as foxtails, glass, metal or wood). We move up the limb feeling the bones and joints one by one until we find the painful area.
In Ashley’s case, the pain was not obvious until we reached the shoulder region. Once we knew which part of the body was affected, we sedated Ashley to take radiographs (x-rays) of the affected area.
Notice the joint mouse on the left
The mouse is in the center of the picture
In these films you can see that there are small fragments of bone located in the joint. These fragments are known as “joint mice”. They arise from a disease called “osteocondrosis dessicans (OCD), which affects large breed dogs during their early growth years. In this disease, the cartilage on the articular (gliding) surface of the joint, becomes loose from the underlying bone. Similar to a skin blister. With time, the “cartilage blister” may tear and the piece or pieces of cartilage will be left floating in the joint. As you can imagine, if the cartilage comes between the two weight bearing surfaces of the bones, it can be quite painful, like having a pebble in your shoe.
The shoulder joint has a an outpouching in the front and rear of the joint. In Ashley’s case, the fragments moved into the rear pouch and probably stayed there for some time. Over time, the cartilage fragments began to absorb calcium and became small bone fragments. With the calcium inside them, they became much harder and therefore more painful when they would slide in between the articular surfaces of the humerus and scapula.
OCD can occur in all the major joints, but happens most frequently in the shoulder, elbow and knee.
We discussed the radiographic findings with Ashley’s owners and agreed to perform a joint exploratory to remove the fragments. Ashley was anesthetized and we opened the joint after some arduous dissection. The stones were right where we expected them to be, and we removed them. The joint surface was a bit irregular where the cartilage had blistered off, but it was relatively smooth. The joint was irrigated and closed with sutures.
Ashley awoke soon after surgery and was up and bearing weight on the limb by the next morning. We administered joint protective agents (adequan and cosequin) and pain relief medication in the form of a non steroidal anti-inflammatory (Deramaxx). We put her on a strict diet to help her lose 10 pounds which should reduce the trauma to the joint. She was discharged with orders to restrict activity severely for 2 weeks.
When we last checked, she was recovering nicely at home.