Suggest Remedy For Severe Pain In Knee

My mother is 58 years old, 5'3"/ 57kgs. She has been quite active physically but two years back she started experiencing pain in her left knee. She got steroid (as we can make out) injected in her knee then. It worked almost fine till last year November when she got her ligament torn near the same area in her left knee when she was getting up from a chair and she straightened her leg. She took rest as suggested by the doctor, but now since April 2011 she has been experiencing extreme pain when she tries to straighten (or fold) her left leg. Once it iss straightened (or folded) the pain reduces.
Please note that she feels the pain only when she tries to straighten (or fold) her left leg and the pain is concentrated in a particular area in her knee (since these 2 years). There is no severe inflammation in the knee, no redness seen or no warmth felt. She has no other joint pain in any other part of her body.
We consulted two Ortheopaedics and a Hopmeopaethic doctor.
Two of the doctors said the bone has grown a little extra whicih is causing trouble, and that it might be the onset of Arthritis. One of the doctors said its because there is some water in her knee and that she should get another steroid injected.
She has thyroid from more than 5 years (TSH). She was regularly taking Calcium tablets, but she stopped taking it since 10-12 months. But now since the doctor has adviced her, its been 2 weeks she is taking Calcim tablets (Calimax ISO) alongwith Jointace DN.