Can Muscle Twitching And Imbalance Be Due To A Head Injury ?

in 1996 I had a motorbike accident and it caused severe head trauma. I had two blood clots removed from the brain . The only long term result is no sense of smell and short term memory loss . Since then I haven t been able to exercise suffiently and lack a sense of balance whilst carrying cups of tea etc. Also recently I seem to have developed a problem with my left knee caused by cycling. The podiatrist has claimed it is a balance issue and referred me to physiotherapy to try strengthen the muscles to help heal and possible prevent future issues with my knees and ankles. To make it worse over the past few weeks I have constant muscle twitchin on my right leg above my knee and slightly right. I now worry that I may have a serious illness or could it just be a common problem with exercise and diet etc. Please advise