Patellar subluxation occurs when the kneecap (the patella) is partially and temporarily dislocated from its normal alignment within the knee joint. Patellar tracking disorder is similar, in that the kneecap is not kept within its normal position, but it occurs on a regular basis as the knee bends and straightens.
The knee is a complex, hinged joint formed by the articulation of three bones, the femur (thighbone), the tibia (shinbone) and patella. Strong ligaments attach the bones to each other, keeping the joint in correct alignment, and tendons run from muscles to bones. Surrounding the joint is a fibrous articular capsule. Within the joint, where the bones come into contact, they are covered with smooth cartilage, enabling them to slide over each other without friction. The patella itself is held within a tendon sheath and ligaments on either side keep it within a groove in the bottom of the femur, called the trochlea. As the knee bends and straightens, the patella slides up and down within the trochlea. If the patella is subjected to an unusual sideways force, it can become subluxated. Patellar tracking disorder occurs when the patella regularly does not move correctly within the trochlea. Both of these conditions result in pain and inflammation.
An abnormality in the structure of the knee, for example the patella or the femur
Underdevelopment of the inner thigh muscles
Overdevelopment of the outer thigh muscles
Overly tight or too loose ligaments and tendons
Severe blow to the side of the knee
If patellar subluxation has occurred due to a traumatic sideways force to the knee:
The kneecap will be obviously out of position, unless it has repositioned itself
Inability to put weight on the leg
Pain on attempting to bend or straighten the knee
If symptoms are being caused by patellar tracking disorder, they may include:
Pain or discomfort, made worse by bending and straightening, or sitting still for a long time
A feeling of the kneecap slipping or catching
A grinding or popping sensation
A feeling that the knee may suddenly give way
Your doctor will ask about your medical history, particularly with regard to any previous knee problems. You will probably be asked about the circumstances of any injury, the onset of your symptoms, their duration and severity and what seems to make them better or worse. The physical examination of your knee will involve the doctor feeling and moving the joint to judge the alignment, stability and tracking of the patella.
X-ray, CT (computerized tomography) and MRI (magnetic resonance imaging) tests might be taken to rule out other possible causes of your symptoms.
Unless surgery is indicated, treatment usually includes the following methods. It is extremely important to take the necessary time to heal properly in order to avoid permanently damaging your knee. Do not rush, and follow professional advice in order to achieve the best outcome.
Rest the knee to allow the ligaments to heal. A knee brace is worn to limit movement and keep the kneecap in its correct position. Crutches may have to be used temporarily to avoid placing too much weight on the leg.
Apply ice packs to the affected knee for twenty minutes at a time, several times a day for the first few days to reduce swelling and relieve pain. Icing the knee after doing rehabilitation exercises is also recommended.
Elevate the knee so that it is above the level of your heart in order to help reduce swelling.
Take over the counter medications (NSAIDs such as ibuprofen, naproxen or aspirin or acetaminophens such as Tylenol) will help with pain and inflammation. Do not give aspirin to anyone under the age of twenty.
Undertake an exercise program, initially under the supervision of a professional, to strengthen the leg muscles, particularly the quadriceps.
If your patellar subluxation or patellar tracking disorder is severe and chronic, surgery may be indicated. Usually damage to the knee can be repaired and the kneecap repositioned to stay in alignment. This is normally a successful procedure in that it makes the knee stable, but it may increase the risk of osteoarthritis in later years.
Your surgeon will discuss with you all the options, risks and likely outcomes of the various surgical procedures available.
Rehabilitation after surgery will include the above treatments, but it will necessarily take longer to return to full mobility.
With prior approval from your doctor or physiotherapist, you can start doing these exercises to increase range of motion in the knee and strength of the supporting muscles. Quad sets:
Tighten the quadriceps muscles at the front of the thigh. Hold for 10 seconds then relax for 3 seconds. Repeat 10 times for 1 set. Do 3 sets. Hamstring stretch:
Standing, place the heel of the affected leg on the seat of a chair. Keep your knee and back straight and bend forwards at the hips until you feel a stretch in the back of the thigh. Hold for 15-30 seconds. Repeat 3 times. Quad stretch:
Standing or lying down, hold the foot of the injured leg and draw it backwards towards the buttocks as far as possible until a stretch is felt in the front of the thigh. Keep the knees together. Hold 30 seconds. Repeat 2-3 times, 3 times a day. Side leg lift:
Lying on your side with the affected leg uppermost and straight, tighten the quadriceps muscles and slowly lift the leg about 10 inches up. Lower slowly. Repeat 10 times for 1 set. Do 3 sets. Straight leg raise:
Sit on the floor with your legs straight out in front of you. Lift the injured leg up off the floor, keeping the knee straight. Hold for 10 seconds then slowly lower. Repeat 10 times for 1 set. Do 3 sets.
Modify your activities or sports participation to avoid those that worsen your condition.
Maintain a healthy weight: Being overweight places extra stress on the joints, in particular the knees and ankles as these bear most of the body's weight.
Warm up and stretch carefully before activity.
Exercise to strengthen the leg muscles that keep your knee in proper alignment, particularly the quadriceps.