The base of the fifth metatarsal Surface Anatomy

Location

The base of the fifth metatarsal is a prominence on the lateral contour of the foot where the peroneus brevis tendon inserts onto the proximal head of the fifth metatarsal. Having the patient evert their foot against resistance makes the tendon more palpable.

Significance

Tenderness, erythema, or swelling at the base of the fifth metatarsal is indicative of peroneal tendinitis or tenosynovitis. You can follow the tendon posteriorly from its insertion behind the lateral malleolus to assess further tenderness associated with peroneal tendinitis, tenosynovitis, or subluxation of the peroneal brevis and longus tendons during active dorsiflexion and plantar flexion of the ankle. Assess any palpable or visible thickening of the tendon, which may be present in more severe cases.