Karate involes little to no throws, but contains standing techniques that include kicking.
Aikido involes wrist and joint malipulations, joint locks, throws and disarms. The theorys behind Aikido are aimed at defence.
My advice would be to talk to your doctor, I don't know what limits, if any, your condition would bring to your study of jujitsu or other martial arts.
If you would be unable to participate in practicing throwing, or being thrown by your fellow students, I would recommend finding out about an instructor that might be able to adjust their syllabus to properly represent your abilities in other techniques.
If however an arrangement cannot be made, possibly a martial art involving standing techniques such as karate would be more suited to your self defence.
The other possibility is with brazilian jiujitsu. This heavily consentrates on ground fighting, gaining dominant positions and submissions such as joint locks, cranks/crushes and strangulation whilst on the ground. With typically a more modern approach to training, you may have more luck finding a professional instructor in this martial art able to adjust the syllubus to suit the needs of the individual.