A Jones fracture is a break occurring in the foot near the base of the fifth metatarsal, the long bone connected to the smallest toe. This injury is known for its difficult healing process due to the unique anatomy of the bone’s blood supply, often resulting in non-union. Unlike many other fractures that heal reliably with simple immobilization, a Jones fracture requires careful management. It is common among athletes participating in sports that require quick changes in direction and forceful pivoting, such as basketball, soccer, and dancing.
Anatomy Where the Jones Fracture Occurs
The Jones fracture involves the fifth metatarsal, the long bone running along the outer edge of the foot. This bone is divided into three parts: the base closest to the ankle, the shaft, and the head near the toes. A true Jones fracture occurs in a precise location called the metaphyseal-diaphyseal junction, where the flared base transitions into the shaft. This break happens approximately 1.5 to 2 centimeters beyond the prominent bony knob, distinguishing it from the more common avulsion fractures.
This specific section is a vascular watershed area, meaning it has a limited blood supply compared to other parts of the bone. The primary blood flow comes from a single nutrient artery, providing a retrograde supply to this proximal section. A fracture here easily disrupts this restricted circulation, compromising the bone’s ability to deliver the cells and nutrients necessary for healing. This inherent lack of circulation is the main reason why Jones fractures are challenging to treat and take a significantly longer time to unite.
Acute Traumatic Causes
The immediate cause of a Jones fracture is a sudden, high-force traumatic event that stresses the metatarsal. The classic mechanism involves a combination of two foot movements: the foot pointing downward (plantar flexion) and the foot turning inward (inversion). This specific position occurs when a person is pushing off, landing from a jump, or pivoting while the heel is slightly raised. For example, a basketball player changing direction or a dancer landing awkwardly on the outer edge of the foot can experience this event.
This combined motion causes a severe bending and twisting force concentrated at the vulnerable metaphyseal-diaphyseal junction. The force is transmitted through the forefoot. The resulting break is often a transverse fracture, meaning the fracture line runs straight across the bone. This acute injury causes immediate, sharp pain, localized swelling, and bruising along the outer mid-foot. The force of the injury is intensified by the pull of tendons and ligaments, such as the peroneus brevis tendon, which can further distract the fracture fragments.
Chronic Stress and Predisposing Factors
While an acute event is often the final trigger, a Jones fracture is frequently preceded by issues that weaken the bone. These factors involve repetitive micro-trauma from activities like long-distance running or high-impact sports, leading to bone weakening over time. This continuous, low-level stress can cause a stress reaction, which is a precursor to a full fracture. The bone is unable to keep up with the constant cycle of breaking down and rebuilding new tissue, creating an area of vulnerability.
Anatomical variations in the foot structure can also predispose an individual to this injury by placing chronic strain on the outer metatarsal. Conditions such as a high-arched foot (cavus foot) or a forefoot that naturally turns inward increase the load transmission to the lateral side of the foot. Other contributing factors overwhelm the bone’s capacity to adapt:
- Poor conditioning.
- A sudden increase in training intensity or volume.
- Running on uneven surfaces.
- Wearing worn-out or improper footwear that lacks adequate arch support or cushioning.