Hi Karen,
Thank you for the kind words.
When a body moves the way it can move that's what becomes natural for you. In other words, if you cannot reach, stretch or bend completely in the manner the asana calls for, it should not matter. There are many who do not have any kind of injury or medical condition who need to spend many months working on form - so it all comes down to the same basic principle:
The muscle strength you have in your healthy muscle tissue will increase and your ability as a Yogi will improve regardless of whether or not you have full use of arms, legs or have had back injuries or other physical conditions. The "good" muscle will still work hard for you - even though it may take time.
What does matter is if this is a permanent condition or not. If it is then the above will apply permanently and your body will develop muscle and increase range of motion in the way that it does best, and is capable of doing, and you will see improvement only with what your body can do. Not to say that some conditions can't be helped by Yoga, because they can, but Yoga is not a cure for any physical problem.
If this not a permanent condition, and there is a full recovery or near full recovery expected, then that changes what you should expect from yourself as a Yogi. Eventually, as you heal, your body will be able to bend, stretch and reach farther and farther, so long as you remain dedicated to your Yoga practice and don't expect too much of yourself too soon.
Pairing Yoga with what your M.D. and/or physical therapist prescribes for you can shorten your recovery time and improve your overall health for the rest of your life.
Stay healthy,
Nancy
BellaOnline Yoga Editor CEO, Nutrabeautiful, Inc. 
