Tiny bones, big problems
Problems with sesamoid bones are often overlooked and sometimes
can be the root of other serious problems for your dog
By Ben J. Character
The most widely known and recognized sesmoid bone is the patella, or kneecap. The patella, and other small bones like it, might be described as glides that not only allow tendons to move smoothly over the turn or angle caused when the joint of the leg bends. They also act similar to a fulcrum to redirect and help increase the amount of force the tendon is capable of exerting. Because of its location, the patella is one of reasons that the quads are such a powerful muscle group.
Each sesamoid bone is a unique intersection of several different tissue types. There are the bones themselves composed a of hard calcified framework of tissues, then each sesamoid has a cartilage surface that interfaces with the cartilage surface of the joint that it traverses. There is the tendon that the sesamoid is contained within and finally the joint capsule, or synovial, tissue that surrounds the whole mechanism and bathes it with joint fluid for lubrication. There are many tendons that have sesamoid bones other than just the patellar tendon, and the ones that we want to focus on are the tiny sesamoids found in the digital tendons of the paws; it is these small sesamoids that can cause big problems.
For pet dogs these little bones seldom cause any problems. In fact, if you were to ask most veterinarians how often they have every diagnosed a problem with sesamoid bones, most would probably consider it a very rare problem. But, for the high performance dog they can actually be quite common and cause problems that go undiagnosed.
Because of the position of these digital sesamoids, as the duration and level of work increases they become more and more susceptible to injury. As the ligaments of the paw and wrist stretch and flex during their continual pounding while at work, they gradually allow slightly more extension of the joints. The increased flexibility eventually allows the higher sections of the foot where the digital sesamoids are located to strike the ground as the foot is placed resulting in injury to them.
These repetitive injuries to the sesamoids can cause many different problems. Fractures are somewhat common, but most simply suffer from traumatic inflammation to one of the components of the sesamoid system (i.e. bone, tendon, joint capsule, etc).
| About Ben Character | |
|
Dr. Character is a freelance writer and private veterinary practitioner
concentrating on sporting dog issues. He has practiced large and small animal medicine and surgery since graduating from Auburn University. Recently, he went on to complete post-doctoral studies at Mississippi State University. Dr. Character is a certified PennHIP member and writes for magazines such as Retriever Journal and Pointing Dog Journal. He is an avid outdoorsman who resides in Union, Alabama, south of Tuscaloosa, with his wife and two children. |
So why are we interested in these sesamo-call-its in our dog's feet? Because, how goes the feet, goes the rest of the leg. The feet, which include all components of the paw from the wrist, or hock, down, are the landing gear for your dog. Each stride your dog takes sends them flying — literally — as all four feet leave the ground during the flight phase of a run. If there are damaged sesamoids causing pain, your dog will be reluctant to land squarely on the sore paw causing a "foot imbalance".
Improper foot balance, will lead to further problems up the limb as weird stresses and strains are transferred up the skeleton. For instance, consider how you would compensate if you had a sore right foot — let's say your heel and big toe (soreness in the heel would necessitate walking on the balls of your feet — which is similar to the stance of the dog and helps our analogy). First, you would want to weight shift to your left foot taking the weight off of your sore foot. To do this you might shorten your stride, limiting the amount of ground contact time for your right foot. Since you could not fully eliminate weight bearing, you would maximize the amount of weight borne to the side of your right foot away from your big toe. In other words, you would walk on the side of your foot — you would "imbalance" your foot.
Do you see how this would place abnormal strain on the joints up the leg and eventually the back itself? Now, think how those forces would be magnified if you tried jumping off your bed and landing on your sore right foot.
This is what happens when your dog has a problem with its digital sesamoid bones. The most common sesamoid injuries are in the fore paws, which bear much of the weight and impact during a dog's run. Because the sesamoids are painful, as your dog runs he knows that landing squarely on that particular foot will hurt. He compensates by shortening his stride, rotating his foot, or using other means to decrease the impact on the sore area. This in turn, sends forces up the leg and through the joints at odd angles placing abnormal stress on ligaments, tendons, joint capsules, and ultimately the back itself. The resulting injury to the carpus, elbow, shoulder, back or other muscles is what most owners and trainers actually notice and decide to have evaluated.
Treatment of sesamoid problems, if discovered, does not require expensive or elaborate measures. Injections around and in the joint, topical applications of steroids and other anti-inflammatories, and physical therapy all help alleviate pain from a damaged sesamoid bone. But, even with appropriate treatment if continued work is performed sesamoid pain will eventually return. If this becomes a recurrent problem, measures can be taken prior to events or hunting to minimize the return of pain. Because of this reoccurrence, some advocate removing the damaged sesamoids, but this has proven to be more detrimental to performance than simply using pre- and post-event treatments.
