Foot Issues

Osteoarthritis of the Ankle

Causes
OA is usually considered a type of degenerative arthritis, or wear and tear arthritis. Doctors consider OA pretty much the same whether it appears years after an injury to the joint or whether it appears without any history of injury. It behaves more or less the same way.

Over the past several years, there has been increasing evidence that OA is genetic, meaning that it runs in families. OA that occurs without any injury may prove to be related to differences in the chemical makeup of articular cartilage. People are born with these differences.

Injury to a joint, such as a bad sprain or fracture, can cause damage to the articular cartilage. The cartilage can be bruised when too much pressure is exerted on it. This damages the cartilage, although if you look at the surface it may not appear to be any different. The injury to the material doesn’t show up until months later. Sometimes the cartilage surface is damaged even more severely, and pieces of the cartilage are ripped from the bone. These pieces do not heal back and usually must be removed from the joint surgically. If not, they may float around in the joint, causing the joint to catch and be painful. These fragments of cartilage may also do more damage to the joint surface.

Once this cartilage is ripped away, it does not normally grow back. Unlike bone, holes in the surface are not simply replaced by the cartilage tissue around the hole. Instead the defects are filled with scar tissue. The scar tissue that forms is not nearly as good a material for covering joint surfaces as the cartilage it replaces. It just can’t support weight and isn’t smooth like true articular cartilage.

An injury to a joint, even if it does not injure the articular cartilage directly, can alter how the joint works. This is true for a fracture where the bone fragments heal differently from the way they were before the break occurred. It is also true when ligaments are damaged that lead to instability in the joint. When an injury results in a change in the way the joint moves, the injury may increase the forces on the articular cartilage. This is similar to any mechanical device or machinery. If the mechanism is out of balance, it wears out faster.

Over many years this imbalance in the joint mechanics can lead to damage to the articular surface. Since articular cartilage cannot heal itself very well, the damage adds up. Finally, the joint is no longer able to compensate for the increasing damage, and it begins to hurt. The damage occurs well before the pain begins.

In summary, arthritis may come from differences in how each of us is put together based on our genes, a condition best described as OA. Or arthritis may develop years after an injury that leads to slow damage to the joint surfaces, a condition probably best described as post-traumatic arthritis. Either way the joint is worn out, and it hurts. For the purposes of this document, we will refer to both types as OA.

Symptoms
Pain is the main problem with arthritis of any joint. This pain occurs at first only related to activity. Usually, once the activity gets underway there is not much pain, but after resting for several minutes the pain and stiffness increase. Later, when the condition worsens, pain may be present even at rest. The pain may interfere with sleep. The joint may swell, fill with fluid, and feel tight, especially following increased activity. As the articular cartilage starts to wear off thejoint surface, the joint may squeak when moved. Doctors refer to this sound as crepitation.

OA will eventually affect the motion of a joint. The joint becomes stiff and loses flexibility. Certain movements can become painful, and it may become difficult to trust the joint to hold your weight in certain positions. The body has a pain reflex such that when a joint is put into a position that causes pain the muscles around the joint may stop workingwithout warning. This reflex can cause a person to stumble or even fall when arthritis affects the ankle joint.

When OA has reached a very severe stage, the bone itself under the articular cartilage may become worn away. This can lead to increasing deformities around the joint. In the final stages, the alignment of the bones can begin to form odd angles where they meet at the joint.