Hypothesis:  Joint Laxity

Joint laxity is suspected in this patient for many reasons.  With coxofemoral 
joint laxity the femoral head is held loosely in the acetabulum.  This laxity can allow for 
subluxation 
of the femur.  Usually this occurs as a combination of genetics and environment.  Genetically the dogs may have shallow acetabuli.  Jocqelyn demonstrated a postive Ortlani sign which is indicative 
of joint 
laxity.  She also experienced the most pain on forced extension which is typical 
of 
coxofemoral laxity.  Jocqelyn had a decreased range of motion, another classic 
sign of joint
laxity.  Jocqelyn, being a 9 month old rapidly growing Rotteweiler fed free 
choice meals, 
makes her a prime candidate for the development of coxofemoral joint laxity.  The increase in weight before the skeleton is mature causes a breakdown in the joint and an already malformed joint is increasingly broken down.     
The laxity 
of the femoral head in the acetabulum would explain the pain after exercising 
because the 
laxity causes incongruity in the joint which can lead to cartilage damage, bone 
remodeling, 
and pain.  As a normal joint moves the articular cartilage should glide along the articular surface smoothly with no rubbing.  If any increase in friction occurs the cartilage starts to be eroded away.  As the cartilage is eroded the friction increases because the articular surfaces are roughened.  Eventually the cartilage is eroded through to the surface of the bone (periosteum), where the nerves are.  Irritation of these nerves causes the pain. As the bone attempts to remodel, osteophytes, mineralized outgrowths of the bone, are produced which interfere with joint movement.  As time progresses the surfaces become more eroded and painful.  In response the bone attempts to remodel further and the destructive cycle continues.

Plan  of Action

Do radiographs of the pelvis and coxofemoral joint, V/D and Lats.