Ankle instability is a condition characterised by the ankle ‘giving way’ or feeling wobbly and unreliable, particularly on uneven surfaces.
The ankle has outer ligaments which stop it from rolling and sliding forward. These ligaments are attached to the fibula (small bone next to the shin bone), the talus (the ankle bone) and the calcaneus (the heel bone). Chronic ankle instability usually develops following an ankle sprain that was not diagnosed properly or has not healed. An ankle sprain stretches and tears the ligaments. When this occurs, small nerve sensors inside the ligament are often damaged. These nerve sensors, called the proprioceptive nerves, give the brain information about the position of the joints. If these nerve endings are not working properly, the brain does not get reliable information and the muscles around the ankle may not work together properly. This causes the ankle to "give way", often with minor stresses. Ankle instability makes patients more prone to ankle sprains, which in turn exacerbate ankle instability. With each ankle sprain, the ligaments are increasingly weakened.
The “giving way” takes place on the lateral, or outer side and will often occur during sports and walking. However, it can also happen while standing and may be accompanied by swelling, discomfort, tenderness and pain.
The foot will be examined for swelling and tenderness and tested for strength by stretching it in various directions. This is called a stress view. X-rays and MRI scans may also be carried out.
Treatment will vary depending on the severity of the injury and the patient’s own activity levels.
This is the first form of treatment and it is generally effective. It is based on retraining the damaged nerves in order to enable them to respond to the movements of the ankle. The strength of muscles around the ankle will also be increased by exercises and activities. To aid the physiotherapy a moulded insole may be worn in the shoe.
This may only be considered if ankle instability fails to improve following physiotherapy or if the ligaments are extremely weak. There are two procedures that surgeons use.
Brostrum’s procedure works through tightening the damaged ligaments and re-attaching them to the bone. It is a highly successful procedure and is appropriate for people with active lifestyles.
The second procedure is known as a tenodesis procedure and should only be used if all other avenues have been explored. It involves taking a strip of the hamstring to create new ligaments. It should only be used as a last resort when the ankle is extremely painful and is under a serious amount of stress. It is an efficient treatment but frequently causes stiffness in the ankle.
Physiotherapy treatment of the unstable ankle is usually effective and results are noticed immediately. Rehabilitation normally involves the patient doing a series of balance exercises of graded difficulty. These exercises stimulate function of the proprioceptive fibres in the ankle. Exercises are performed on different surfaces, sometimes on wobble boards and with eyes open or shut. Taping of the ankle can also be effective to aid the process of rehabilitation. Gentle transverse frictions to the damaged ligaments are often used to stimulate healing. Electrotherapy devices such as ultrasound are sometimes also used to help reduce scarring in damaged ligaments and stimulate healing.