A navicular stress fracture is one of the most common stress fractures affecting athletes, especially those in explosive events such as sprinting and jumping.
Navicular stress fracture symptoms
Symptoms of a navicular stress fracture include poorly localized ache in the midfoot which gets worse with exercise. Pain may radiate along the inside arch of the foot and goes away quickly with rest only to return again as training resumes. Tenderness may be felt when the thumb is pressed into the top of the foot over the navicular bone, called the N spot.
Navicular stress fracture explained
The navicular is one of the tarsal bones in the ankle. It sits on top of the calcaneus or heel bone. A stress fracture of the navicular is caused by over use or repetitive strain, usually from high impact sports such as sprinting, hurdling and jumping. Poor technique or training errors can also contribute to the likelihood of sustaining a stress fracture of the foot.
The exact mechanism of injury is not known although it is thought the navicular bone gets pinched or impinged between the bones to the front and back of it causing it to be compressed. If the athlete has a reduced range of dorsi flexion (moving the foot upwards) in the ankle then they are more susceptible to a navicular stress fracture as the midfoot has to compensate for the lack of movement.
Navicular stress fracture treatment
Treatment of a navicular stress fracture may depend on severity. It the injury is classed as a stress reaction where the outer part of the bone has not fractured then weight bearing rest in a walking splint may be recommended until symptoms have gone followed by a gradual return to full fitness.
If a stress fracture is diagnosed then complete non weight bearing in a full cast for a period of 6 weeks is essential. After 6 weeks the N spot over the top of the navicular bone is felt. If it is tender then the cast is re-applied for a further 2 weeks non weight bearing.
If there is a separation of the navicular bone or the fracture fails to heal then surgery may be required to fix the bone with a pin or screw.
Rehabilitation of a navicular stress fracture
Once the cast has been removed it is important to mobilize the foot and ankle which will have been kept still for at least 6 weeks. Ankle mobility exercises and strengthening exercises should be done before starting to run again. Calf raises and exercises for the small muscles in the foot are important. Sports massage for the calf muscles can help restore them more quickly to normal function speeding up the rehabilitation process.
It is also important to eliminate factors which are likely to cause the injury to recur. Training errors in terms of technique or over training should be identified. A podiatrist can check if there are any biomechanical factors such as over pronation of the foot which should be corrected with orthotic inserts in the shoes. Tarsal coalition where the tarsal bones fuse together as well as restricted dorsi flextion of the ankle will also make the athlete more susceptible to a future navicular stress fracture.
When full ankle mobility and basic strength of the joint has been restored which will usually take a week or more then running can resume. Training should be very very gentle to start with aiming to build up to resuming normal training loads over a period of at least 6 weeks.