Fifth Metatarsal Base Stress Reaction (Pre-Stress Fracture – Pre-Jones Fracture)
Background
One cause of pain on the outside of the midfoot is a stress reaction of the base of the fifth metatarsal (Figure 1). This is essentially a pre-stress fracture (pre-Jones fracture). This lateral foot pain is caused by microscopic fracturing of the bone that is not visible on plain x-ray. Patients will often describe an achy pain. They often report a recent increase in weight-bearing activities such as a new training program or a new job that requires prolonged standing.

Physical Examination
Patients with a fifth metatarsal stress reaction may have some generalized discomfort on the outside of the midfoot. They may also have a higher arched foot shape as this foot shape will tend to cause increased loading over the outside part of the foot with standing and walking. Usually, patients will be able to stand and walk and do many of their normal activities, although this may increase their discomfort. Strength and movement are usually normal.
Imaging Studies of a Fifth Metatarsal Base Stress Reaction
Plain weight-bearing x-rays of the foot are usually normal. They may demonstrate evidence of a high arched foot pattern. It is important to obtain these x-rays in order to rule out a Jones Fracture.
If the diagnosis is in question, an MRI can help differentiate a fifth metatarsal stress reaction from a Jones fracture. In patients with a fifth metatarsal base stress reaction, an MRI will show edema (increased blood) in the bone at the base of the fifth metatarsal. However, no obvious fracture line will be seen. An MRI may also identify other sources of pain in the outside of the foot.
Treatment of a Fifth Metatarsal Base Stress Reaction
Provided that the diagnosis of a fifth metatarsal stress reaction is made prior to it becoming a clear stress fracture (Jones type fracture) non-operative treatment is usually successful. Initial treatment is to back off any weight-bearing activities. Relative immobilization of the foot should be started by having the patient wear either a walker boot or a stiff-soled comfort shoe. Risk factors for a stress reaction or stress fracture should be assessed. This includes testing for osteoporosis and vitamin D deficiency. It is important to treat these factors if they are present. Generally, patients with a fifth metatarsal stress reaction will require a 3-6 week of limited activities depending on the extent of the stress reaction. Once the patient has no symptoms and there has been adequate time for bone healing. The patient may begin a graduated increase in activity levels.
October 9th, 2024