Q After training for and running several marathons every year with no problems, my left foot suddenly started flapping forward on a run. I was diagnosed with drop foot - although there was no explanation why. An MRI scan shows no damage but I'm in a lot of pain. How long before I can run again?
A Drop foot describes an abnormal neuromuscular disorder affecting someone's ability to raise their foot at the ankle. It is characterised by an inability to point the toes toward the body (dorsiflexion) or move the foot inward or outward at the ankle. This loss of function may be accompanied by pain, weakness and numbness, with the result that running becomes a challenge.
Drop foot is not a disease as such, but a symptom of an underlying problem. Depending on the cause, it may be temporary or permanent, although I would hope in your case that you will notice some improvement soon.
Drop foot is usually caused by injury to the peroneal nerve deep within the lumbar and sacral spine. This nerve is a branch of the sciatic nerve, and runs along the outside of the lower leg below the knee and branches off into each ankle, foot and first two toes. It transmits signals to the muscles responsible for ankle, foot and toe movement and sensation, so any problems that arise from it are felt in these areas. The injury might be due to a direct blow or a repetitive strain injury, and even due to a particular running style that may trigger nerve problems over time.
One other possible diagnosis is chronic exertional compartment syndrome, often misdiagnosed as "shin splints". Repetitive activity, such as running, causes tissue in the affected muscle area, or compartment, to swell. That leads to a decreased blood supply to the muscles, injuring the muscle and nerves and sometimes causing drop foot. A complete rest from running plus anti-inflammatory medication may help but an orthopaedic consultant with a special interest in sports medicine will be able to tell you if the area needs scanning, what treatment you require and when you will be able to resume running.
Dr Roger Henderson, GP and marathon runner