Mondo Description Osteoarthritis of the foot generally affects the joint at the base of your big toe. It can cause your toe to: - become stiff over time, which can make it difficult and painful to walk – this is called hallux rigidus - become bent, which can lead to painful bunions (bony lumps at the base of your big toe) – this is called hallux valgus. Osteoarthritis of the mid-foot is also quite common, especially in older people, and may cause an obvious bony swelling (osteophyte) on the top of your mid-foot. Ankle osteoarthritis is least common and may cause your heel to move to an unusual angle.