Arthritis
Arthritis is the irritation and inflammation of a joint. As the foot has thirty-three joints (there are a LOT of little bones in there) and the knees are the largest joints in the human body, arthritis can cause quite a few problems in the lower limb.
The word breakdown on this one is remarkably quaint, although not particularly informative. The first half comes from the Greek arthron meaning joint or articulation. The ending -itis is a pretty common suffix referring to inflammation or pain. So, the word arthritis tells us about the symptoms and the location, but not at all about what is actually happening.
Joints are the place where two bones meet. Often the bones will be able to move in relation to each other, like wiggling your toes or bending your knees. These types of joints are called synovial joints and are characterized by a fibrous capsule that covers the entire articular area where the bones meet. This creates a little pouch that is filled with lubricating synovial fluid, which, coupled with the very, very smooth hyaline cartilage that acts as an end cap for the articulating bones, makes for very efficient and friction free movement at the joint. The closest comparison I can come up with is: imagine two cue balls sliding across each other in a bag full of grease. That is what a healthy knee joint is like on the inside, just unbelievably smooth, effortless motion.
Arthritis is when the structures that allow such easy motion break down. There are three types of arthritis that are common in the lower limb: osteoarthritis, rheumatoid arthritis, and gout.
Osteoarthritis is essentially mechanical breakdown of the cartilage surfaces of the joints. Put simply, it is wear and tear. Rub the working parts of the joints together through decades of standing, walking, bending, running and lifting and eventually they will start to break down. The smooth hyaline cartilage becomes rough, the joint capsule becomes stiff, or the cartilage can get worn away entirely resulting in bone grinding directly against bone. This is very common in the knees and hips and is often felt as pain, stiffness and reduced range of motion.
Rheumatoid arthritis is when the body's immune system attacks the joint structures, particularly the joint capsule. This can lead to swelling which can in turn damage other tissues within the joint. This is characterized by red, swollen joints that feel hot and painful. Rheumatoid arthritis typically affects joints closest to the ends of the limbs, such as the toes, the middle of the foot and the ankle.
Gout is when a substance called uric acid is not properly processed by the kidneys and gets deposited as crystals in the fluid within the joint capsule. This results in the normally slick, clear fluid becoming gritty and thick as the sharp, little crystals gum up the works. Gout symptoms can come and go in waves and are dependent on a number of factors, mainly diet and metabolism.
A pedorthist can help manage these conditions by providing bracing or custom orthotics that will help to limit some of the motions of the damaged joint tissues. Firm arch support and a deep heel cup in a pair of orthotics can help to reduce midfoot and ankle pain. Orthotics can also be used to alter knee mechanics and take pressure off of the inner or outer knee to mitigate pain and improve mobility. Compressive braces can decrease swelling and pain in the ankle and knee, while certain off-loader style braces can significantly reduce knee pain caused by damaged cartilage.
