Hallux valgus is a common forefoot deformity in which the first metatarsal deviates medially and the hallux deviates both laterally and into pronation, leaving a prominence on the medial side of the forefoot at the first metatarsal head. The causes of hallux valgus in most patients are believed to be multifactorial including an intrinsic predisposition to develop a bunion along with a history of extrinsic deforming factors.
Anatomy and Pathogenesis
The stability of the first ray depends upon a balance of static and dynamic structures. Loss of stability anywhere along the length of the first ray can contribute to hallux valgus. In addition to the bony architecture of the first tarsometatarsal (TMT) and first metatarsophalangeal (MTP) joints, several soft-tissue structures contribute to joint stability (Table 1
). The four requirements for stability of the first ray are a congruent and stable MTP joint, a distal metatarsal articular angle (DMAA) that encourages stability, balanced static and dynamic constraints, and a stable TMT joint.1
Hallux valgus typically progresses in a stepwise fashion. The process is believed to begin with attenuation of the medial soft-tissue supporting structures of the MTP joint (abductor hallucis and the medial joint capsule). As a result, the first metatarsal drifts into varus and the first MTP joint subluxes laterally. Progressive deformity often occurs as the medial supporting structures attenuate further and the lateral structures begin to contract. As the first metatarsal drifts into varus, the sesamoids, which are tethered by the transverse metatarsal ligament, displace into the first intermetatarsal space. This causes pronation of the hallux. Moderate to severe hallux valgus deformity can significantly compromise the weight-bearing capacity of the first ray, resulting in transfer of weight from the first MTP joint to the adjacent lesser MTP joints.
Numerous factors are believed to contribute to the development of hallux valgus. The possible intrinsic etiologies include metatarsal head morphology, metatarsus primus varus, hypermobility of the first TMT joint, pes planus, generalized ligamentous laxity, tight Achilles tendon, inflammatory arthropathies, and neuromuscular disorders. Heritable anatomic factors such as DMAA, hypermobility, and arch height are believed to have an important role in the development of hallux valgus. Juvenile hallux valgus is more linked to heritable factors than adult hallux valgus. The extrinsic factors that contribute to hallux valgus include poorly fitting shoes that force the toe into an abnormal posture and acute trauma that disrupts the medial capsule, abductor hallucis, or sesamoid complex or fractures of the medial base of the proximal phalanx.
A much higher prevalence of hallux valgus has been observed in women than in men. Women wearing fashionable shoes with an elevated heel or narrow toe box may be largely responsible for this sexual dimorphism. In addition, fundamental anatomic differences between women and men may further predispose women to the development of hallux valgus. In general, women have a smaller and rounder metatarsal head, an adducted first metatarsal, and higher rates of ligamentous laxity than
men. Studies report a ratio as high as 15 women to every 1 man treated operatively for this problem.2
As compared to women, men who have surgery for hallux valgus are typically younger and more likely to have a family history of hallux valgus. Radiographic measurements have shown a larger deformity in men having surgery for hallux valgus than in women as well as a higher rate of first MTP joint congruence.
TABLE 1 Soft-tissue Stabilizers of the First Tarsometatarsal and First Metatarsophalangeal Joints
First Tarsometatarsal Joint
First Metatarsophalangeal Joint
Flexor hallucis longus
Intrinsic muscles of the foot
Extensor hallucis brevis
Extensor hallucis longus and extensor hood
Flexor hallucis brevis and sesamoid complex
Medial and lateral collateral ligaments
Transverse metatarsal ligament
Patients with hallux valgus typically present with pain over the medial eminence. The patient also may have generalized pain at the first MTP joint, pain from associated lesser toe abnormalities such as hammer toes, or pain at the lesser metatarsal heads caused by abnormal physiologic loading (transfer metatarsalgia). Skin lesions caused by chafing from shoes are common. Guidance and care should be tailored to the patient’s symptoms, limitations, goals, and expectations.
The physical examination should include a standing assessment of alignment and a careful inspection for skin lesions including callosities. Neurologic and vascular status should be evaluated for all patients. The specific location of pain should be determined based on direct palpation as well as history. Joint motion and passive correction of the deformity are assessed. To evaluate for contractures, it is important to determine the dorsiflexion and plantar flexion of the first MTP joint in a reduced position. Intrinsic causes of hallux valgus should be assessed by examining for hypermobility of the first TMT joint, pes planus, generalized ligamentous laxity, and a tight Achilles tendon. Patients should also be evaluated for a history of inflammatory arthropathy or neuromuscular disorders.
Weight-bearing AP, lateral, and oblique foot radiographs should be obtained. The AP view is used to measure the intermetatarsal angle, hallux valgus angle, DMAA, and hallux valgus interphalangeus angle (Figure 1
). The deformity is classified as mild, moderate, or severe (Table 2
). The alignment of the sesamoids under the first metatarsal head is assessed. It is important to determine whether the first MTP joint is congruent or incongruent (Figure 2
). In a congruent deformity, there is a concentric relationship between the first metatarsal head and the base of the proximal phalanx. An incongruent deformity
occurs when the hallux is laterally subluxated on the metatarsal head. Finally, the first MTP joint should be evaluated radiographically for arthritic changes.
FIGURE 1 Standing AP radiograph shows the angles measured in hallux valgus. HVA = hallux valgus angle, IMA = intermetatarsal angle.
TABLE 2 Radiographic Angles Used to Measure the Severity of Deformity in Hallux Valgus
Severity of Deformity
Hallux Valgus Angle
First-Second Intermetatarsal Angle
Distal Metatarsal Articular Angle
20° to 40°
11° to 16°
Instability of the first TMT joint is diagnosed primarily by clinical assessment, although efforts continue to develop an objective way to measure this.3
Several different devices can be used to measure sagittal plane motion.4
A study of a mobile fluoroscopic device used to analyze first ray motion in the sagittal plane during gait found that patients with hallux valgus had increased maximal dorsiflexion of the first TMT.5
Recently, weight-bearing CT imaging has identified increased motion in multiple joints along the first ray, including the first TMT joint, in patients with hallux valgus as compared with a control group.6,7
FIGURE 2 Standing AP radiographs show a congruent (A) and an incongruent (B) hallux valgus deformity.