Sudden knee pain pulling sensation in back of knee

[Lindarhasa]

I am woman in my 50' s and work night shift in supermarket which involves being on my feet for 10 hours a lot of lifting, kneeling and getting up and down off the floor. A couple of years ago i had a spate of Prepatella Bursitus which cleared up and hasnt returned.

3 weeks ago whilst on shift, had been working for an hour or so my left knee unexpectedly completely gave way. This continued happening throughout the shift at fairly regular intervals, my knee felt unstable and painful in the front of my knee and if something was moving out of place.

The following day my was knee was badly swollen on the left hand side above my kneecap. Saw my gp and following xrays and various manipulations of my leg he has diagnosed osteo-arthritis he has given pain killers, anti inflamm's and exercises to strengthen my knee. The swelling has gone down considerably but the symptons have changed.

Now 3 or 4 times a day, usually whilst walking up and down stairs slowly and steadily but also at other times, i will without warning get excruciating pain and a very strong pulling/tearing sensation in the back of my knee. The pain only lasts for a few minutes but i am unable to bear any weight on that leg or straighten it during that time. Once the pain has subsided i can walk normally although the back of my knee remains very sore and my knee cap feels unstable (as it does most of the time) and later on my leg aches from knee down to ankle. The pain during these episodes is lasting for longer and longer.

My gp did ask if i had knocked or injured my knee at all and i said no but a colleague has reminded me that about 9 months ago i fell at work and landed left knee bent on a metal bar, the left knee/upper front of left leg took the full impact. My knee was swollen and painful but recovered after a few days.
Sorry to be long winded. Are these the symptoms of ostea arthritis, is the fall relevant. Many Thanks

[Heidi]

Sounds like a patella problem, maybe mal-tracking, maybe actually subluxations.
The only thing that doesn't quite fit is pain at the back of the knee joint. IS there anywhere at the back of the knee joint that is tender to touch?
Try stretching your quad and groin muscles and strengthening VMO and the hip abductors. You will find info on how to do this on our patellofemoral pain pages.
A knee support may also help. Make sure you get one with an open knee at the front, which has padding surrounding the knee cap to stabilise it.