What is a Heel Spur?
A heel spur is a bony protrusion that forms where the fascia tissue connects to the heel bone. The bony protrusion is a result of calcium deposits that build up over time on the underside of the heel bone.
When discussing heel spurs, we look at two distinct types and the heel spur location. There are the more common bone spurs on the bottom of the heel, and the more difficult to treat bone spurs on the back of the heel.
So, what are spurs? Spurs are additional growths of bone, not just calcium deposits as some patients have asked me about. Bone is made of many minerals like phosphorous including calcium, collagen and matrix of hydroxylapatite and more. Calcium deposits are just calcium and can be found in many areas of the body. BUT bone is NOT just calcium. So, spurs are not just calcium but TRUE bone.
Specifically, this blog will discuss bone growths coming off the calcaneus or heel bone. Bone is a living organism and like all parts of the body will grow larger when there is force or stress on it. (Wolff's law, developed by the German anatomist and surgeon Julius Wolff (1836–1902) in the 19th century, states that bone in a healthy person or animal will adapt to the loads under which it is placed.) In other words, as the heel bone has stress applied to it, it will grow additional bone to handle the stress.
Types of heel spurs
1. Plantar heel spurs
Heel spurs on the bottom of the heel are known as "plantar" heel spurs. Plantar means the bottom of the foot. Heel/bone spurs on the back of the heel are known as "posterior" heel spurs. The theory of plantar heel spurs is that excess force from the plantar fascia, which connects to the heel bone, causes the spur to grow. One theory is that as the foot pronates (when the foot rolls in and the arch lowers), the foot lengthens as the arch drops. This causes the plantar fascia to be stretched and pulls on its insertion on the heel bone. Another theory is that dysfunction of the big toe joint, which is the other end of the plantar fascia, causes the fascia to again pull on the heel when we walk. There are also diseases that can cause heel spurs, such as ankylosing spondylitis which is a type of arthritis.
2. Posterior heel spurs
Heel spurs on the back of the heel, also known as posterior heel spurs, are located where the achilles tendon attaches to the heel bone. The theory is that excess pull on the achilles from its muscle attachments in the leg (gastrocnemius and soleus) causes stress to the heel bone causing heel spur at the achilles/heel bone interface. What is the reason for excess force on the achilles tendon? Here again, pronation of the foot plays is the cause. One major function of the two leg muscles that attach to the achilles (gastrocnemius/soleus) is to decelerate or reduce pronation of the foot when walking or running. When there is excess pronation (which has many causes), the muscles overwork and put extra strain on the achilles causing bone spurs on the back of the heel. Another cause of posterior heel spurs is some types of arthritis.