Unfortunately I can give a first hand description of bunion formation. Having a personal interest I have thoroughly researched this deformity. Hallux is Latin for our big toe and valgus is a deformity that describes a movement of a bone towards the mid-line of the body. This is the same deformity that occurs in ‘knock-kneed’ when the shin bone moves away from the centre of the body. In hallux valgus it is actually the metatarsal bone of the big toe that first moves medially and then the big toe compensates by moving in the opposite direction towards the second toe [Fig. 1]. This causes the charactaristic boney lump at the base of the toe, which is actually the protruding head of the metatarsal bone. Its common name is a bunion.
Bunions most commonly occur in females but not because of the popular belief that they are caused from wearing high heels. High heels are undoubtably bad for almost every joint in your body including you big toe. However, I have known quite a few men with hallux valgus and I am almost 100% sure that they were not cross dressers! Once a bunion has formed wearing tight shoes (or high heels) will aggravate it and often causes redness, pain and swelling. The difficulty is that with this deformity many shoes will be too narrow to fit your wider foot.
There is a strong hereditary factor with bunions. However, the inherited disorder is usually one of connective tissue expressing ligamentous laxity and resulting in joint hypermobility. Joint hypermobility indicates a deficiency in the passive stabilisation system of the whole body. This condition overloads all the bony structures and in this case usually involves all the joints of the lumbar spine, pelvis, hips, knees and the feet. It is the laxity of the connective tissue in the feet that allows the first metatarsal of the big toe to wander medially leading to the valgus deformity [Fig. 1].
This problem starts at the pelvis. With their wider pelvis and increased Q-angle it is this factor that makes females at a higher risk of forming bunions. Our pelvis is the major control centre for our posture and inevitably effects the whole of the rest of the body. You will usually find a pelvic tilt in those with bunions. A pelvic tilt is highly correlated with an exaggerated lumbar lordosis, which affects abdominal wall strength and function. This in turn effects lower extremity posture and increases the incidence of injury to the lower extremities. The usual postural pattern with a hallux valgus is an anterior tilt of the pelvis (often one-sided), an internal rotation of the leg/knee, pronation of the foot and a big toe valgus.
It is important to start by correcting the pelvic tilt, with therapy if it is one sided. If bilateral you will need to simultaneously strengthen the abdominal muscles and the hip extensor muscles. This will contribute greatly to correcting your internally rotated legs and foot pronation. You can aid correcting the feet by practising walking with your toes lifted off the floor. The tendons of your inner arch belong to your toe extensors so strengthening them will help to strengthen the inner arch of your foot. Sensibly avoid tight shoes and high heels.
A condition that often accompanies hallus valgus and arises later on as a result of it is hallux rigidus. As the name suggests the deformed joint becomes degenerated and rigid. This is partially due to the compromised toe-off in the first stance of walking, and is exacerbated by the excess wear and tear of hypermobility. Rolling over the toes as we do when transiting from Rod to Upward Facing Dog is ideal to help in the prevention of hallux rigidus.
Figure 1: Medial deviation of metarsal bone with lateral deviation of phalanges.