I was trying to get in the back of my Dad’s pick-up truck when I felt a pop in my knee. I had my foot up on the tailgate with my knee fully bent. The pop occurred as I started to straighten my leg to hoist myself up. It swelled up right away. I’m in the ER with my parents waiting to find out if I need surgery. They said it is a sleeve knee fracture. What would happen if I didn’t have an operation? Could I heal on my own? [Sent by my Blackberry].

With a sleeve fracture, the quadriceps tendon is torn so severely, it separates from the muscle and takes a piece of the cartilaginous patella with it. It also takes the top layer of bone called the periosteum. When the periosteum is peeled away with a fragment of the underlying bone still attached, it is called a sleeve avulsion.

A little anatomy might help explain what happened and why surgery is usually required. The quadriceps tendon is wrapped around the kneecap to hold it in place. At the upper end, the tendon is attached to the large four-part quadriceps muscle along the front of the thigh.

Together, the quadriceps muscle and its tendon extend or straighten the knee. The quadriceps tendon continues down below the knee cap where it inserts or attaches to the tibia (lower leg bone). The patella acts like a pulley system to help the quadriceps muscle pull the lower leg up in order to straighten the knee.

Surgery is usually needed to bring the pieces of the patella back together (reduction) and hold them in place with pins or screws (internal fixation) until healing takes place. The procedure is called open reduction and internal fixation or ORIF. The leg is put in a cast with the knee straight for about six weeks. Physical therapy begins as soon as the cast is removed. Restoring full knee motion and strength are the two main goals of therapy.

With careful placement of the sleeve fracture during surgery, normal quadriceps function is possible. Improper treatment can result in deformity and poor timing of the quadriceps’ ability to contract and release normally.

Conservative (nonoperative) care may be possible in skeletally mature patients (bones have stopped growing) if there is no change in the fragment position as the knee bends and straightens. In order to know if the fragment moves, the knee must be observed under fluoroscopy, a special type of 3-D X-rays that allow the surgeon to see the joint as it moves.

Without surgery, the patella may end up shifting location (moving up or down depending on which type of sleeve fracture occurred). The quadriceps may develop an extensor lag and start to atrophy (weaken and waste away). An extensor lag means the quadriceps tendon that straightens the joint doesn’t pull back far enough to get full knee extension. The knee remains slightly flexed no matter how hard the person tries to straighten it.

The decision to do surgery is determined by your age, the extent of damage, and your activity level (participation in sports is a big factor). Most children and teens gain back their motion and strength after surgery within the first two to four months. Excellent results have been reported in most cases.