What is the patella, and what does it do
The patella (kneecap) is the moveable bone on the front of the knee. This unique bone is wrapped inside a tendon that connects the large muscles on the front of the thigh, the quadriceps muscles, to the lower leg bone. The large quadriceps tendon together with the patella is called the quadriceps mechanism. Though we think of it as a single device, the quadriceps mechanism has two separate tendons, the quadriceps tendon on top of the patella and the patellar tendon below the patella.
Tightening up the quadriceps muscles places a pull-on the tendons of the quadriceps mechanism. This action causes the knee to straighten. The patella acts like a fulcrum to increase the force of the quadriceps muscles.
The underside of the patella is covered with articular cartilage, the smooth, slippery covering found on joint surfaces. This covering helps the patella glide (or track) in a special groove made by the thighbone, or femur. This groove is called the femoral groove.
Two muscles of the thigh attach to the patella and help control its position in the femoral groove as the leg straightens. These muscles are the vastus medialis obliquus (VMO) and the vastus lateralis (VL). The vastus medialis obliquus (VMO) runs along the inside of the thigh, and the vastus lateralis (VL) lies along the outside of the thigh. If the timing between these two muscles is off, the patella may be pulled off track.
What causes this problem?
Problems commonly develop when the patella suffers wear and tear. The underlying cartilage begins to degenerate, a condition most common in young athletes. Soccer players, snowboarders, cyclists, rowers, tennis players, ballet dancers, and runners are affected most often. But anyone whose knees are under great stress is at increased risk of developing chondromalacia patella.
Wear and tear can develop for several reasons. Acute injury to the patella or chronic friction between the patella and the femur can result in the start of patellofemoral pain syndrome. Degeneration leading to chondromalacia may also develop as part of the aging process, like putting a lot of miles on a car.
The main cause of knee pain associated with patellofemoral pain syndrome is a problem in the way the patella tracks within the femoral groove as the knee moves. Physical and biomechanical changes alter the stress and load on the patellofemoral joint.
The quadriceps muscle helps control the patella so it stays within this groove. If part of the quadriceps is weak for any reason, a muscle imbalance can occur. When this happens, the pull of the quadriceps muscle may cause the patella to pull more to one side than the other. This in turn causes more pressure on the articular cartilage on one side than the other. In time, this pressure can damage the articular cartilage leading to chondromalacia patella.
Weakness of the muscles around the hip can also indirectly affect the patella and can lead to patellofemoral joint pain. Weakness of the muscles that pull the hip out and away from the other leg, the hip abductor muscles, can lead to imbalances to the alignment of the entire leg – including the knee joint and the muscle balance of the muscles around the knee. This causes abnormal tracking of the patella within the femoral groove and eventually pain around the patella. Many patients are confused when their physiotherapist begins exercises to strengthen and balance the hip muscles, but there is a very good reason that the therapist is focusing on this area.
A similar problem can happen when the timing of the quadriceps muscles is off. There are four muscles that form the quadriceps muscle group. As mentioned earlier, the vastus medialis obliquus (the muscle on the inside of the front of the thigh) and the vastus lateralis (the muscle that runs down the outside part of the thigh) are two of these four muscles. People with patellofemoral problems sometimes have problems in the timing between the VMO and the VL.
The VL contracts first, before the VMO. This tends to pull the patella toward the outside edge of the knee. The result is abnormal pressure on the articular surface of the patella.
Another type of imbalance may exist due to differences in how the bones of the knee are shaped. These differences, or anatomic variations, are something people are born with. Doctors refer to this the “Q angle”. Some people are born with a greater than normal angle where the femur and the tibia (shinbone) come together at the knee joint. Women tend to have a greater angle here than men. The patella normally sits at the center of this angle within the femoral groove. When the quadriceps muscle contracts, the angle in the knee straightens, pushing the patella to the outside of the knee. In cases where this angle is increased, the patella tends to shift outward with greater pressure. This leads to a similar problem as that described above. As the patella slides through the groove, it shifts to the outside. This places more pressure on one side than the other, leading to damage to the underlying articular cartilage.
Problems at the foot level can also contribute to poor tracking of the patella. If the long arch of the foot is too flat or weak, the foot will roll in during gait, a situation called over-pronation. This causes the tibia to rotate inwards causing a change in the angle of the femur and tibia and altering the pull of the muscles. This causes increased pressure and poor functional alignment of the patella during walking or running similarly to increases in “Q” angle as described above.
Finally, anatomic variations in the bones of the knee can occur such that one side of the femoral groove is smaller than normal. This creates a situation where the groove is too shallow, usually on the outside part of the knee. People who have a shallow groove sometimes have their patella slip sideways out of the groove, causing a patellar dislocation. This is not only painful when it occurs, but it can damage the articular cartilage underneath the patella. If this occurs repeatedly, degeneration of the patellofemoral joint occurs fairly rapidly.
What does chondromalacia patella feel like?
The most common symptom is pain underneath or around the edges of the patella. The pain is made worse by any activities that load the patellofemoral joint, such as running, squatting, or going up and down stairs. Kneeling is often too painful to even try. Keeping the knee bent for long periods, as in sitting in a car or movie theater, may cause pain.
There may be a sensation like the patella is slipping. This is thought to be a reflex response to pain and not because there is any instability in the knee. Others experience vague pain in the knee that isn’t centered in any one spot.The knee may grind, or you may hear a crunching sound when you squat or go up and down stairs. If there is a considerable amount of wear and tear, you may feel popping or clicking as you bend your knee. This can happen when the uneven surface of the underside of the patella rubs against the femoral groove. The knee may swell with heavy use and become stiff and tight. This is usually because of fluid accumulating inside the knee joint, sometimes called ‘water on the knee’. This is not unique to problems of the patella but sometimes occurs when the knee becomes inflamed.
How do health care providers diagnose the problem?
Diagnosis begins with a history and physical exam. Your physiotherapist will try to determine where the pain is located and if you have any grinding, clicks or pops with knee movement.
Some patients may be referred to a doctor for further diagnosis and treatment.
Once your diagnostic examination is complete, the physiotherapists have treatment options that will help speed your recovery, so that you can more quickly return to your active lifestyle.
Non-operative treatment is usually recommended for this problem. Although the time required for recovery varies, patients with chondromalacia often benefit from approximately four to six weeks of physiotherapy. The aim of treatment is to calm pain and inflammation, to correct muscle imbalances, and to improve function of the patella.
Getting the pain and inflammation under control is the first step. It is important for you to understand the need to keep your activity level below what will trigger more pain and tissue damage. You may need to ice your knee during the day and limit certain activities such as stairs, squatting, or running. The overall goals of Physiotherapy rehabilitation will be to improve muscle function and flexibility while providing pain relief or pain control.
Your physiotherapists may suggest rest and anti-inflammatory medications, such as aspirin or ibuprofen, especially when the problem is coming from overuse. Acetaminophen (Tylenol®) may be used for pain control if you can’t take anti-inflammatory medications for any reason. Your physiotherapist may also use ice massage and ultrasound to limit pain and swelling.
Your physiotherapist will examine your standing leg alignment and watch how you walk, run, or climb stairs in order to determine which areas of the leg are weak or imbalanced. The goal will be to correct any muscle length, strength or timing issues in order to prevent the condition from returning or worsening.
Activity modification, flexibility, and strengthening are key parts of our rehabilitation program. Good results can be expected when working slowly but steadily on flexibility and strengthening exercises. The motto of no pain, no gain does not apply to this problem.
The most successful program is one of common sense. If an activity causes pain, then reduce the frequency, intensity, or duration of that activity until you are once again pain free. We will help you to gradually build up what you can do while maintaining your pain free status.
Bracing or taping the patella can help you do exercises and activities with less pain. Most braces for patellofemoral problems are made of soft fabric, such as cloth or neoprene. You slide them onto your knee like a sleeve. A small buttress pads the side of the patella to keep it lined up within the groove of the femur.
An alternative to bracing is to tape the patella in place. Our physiotherapist applies and adjusts the tape over the knee to help realign the patella. The idea is that by bracing or taping the knee, the patella stays in better alignment within the femoral groove. This in turn is thought to improve the pull of the quadriceps muscle so that the patella stays lined up in the groove. Patients report less pain and improved function with these forms of treatment. Taping or bracing is usually temporary and used only until the muscles can effectively maintain optimal alignment of the patella again.
As the pain and inflammation become controlled, we will work with you to improve flexibility, strength, and muscle balance in the knee. Muscle imbalances are commonly treated with stretching and strengthening exercises but improvement usually takes at least six to eight weeks. You may then need to continue a modified program of flexibility and strengthening exercises to maximize control and strength of the quadriceps muscles. This type of program is typically done two to three times each week, and, although the time required for recovery varies, you may need this type of physiotherapy for several months (or longer if you continue to experience pain during progressive sports participation).
Quadriceps strengthening exercises that address deficits in knee extension strength include non-weight-bearing single-joint (e.g., knee extension) and weight-bearing multiple-joint exercises (e.g., seated leg press).
Non-weight bearing exercises are also known as open kinetic chain exercise. Weight-bearing exercises are referred as closed-chain exercise. Closed-chain exercises place less stress on the patellofemoral joint and may be used first to achieve improved function before progressing to open kinetic chain exercises. Studies also show greater VMO activity with closed kinetic chain exercise. And a closed-chain exercise program also addresses hip muscle weakness at the same time as knee muscle deficits.
Your physiotherapist will adjust your rehab program to provide you with the most pain free and effective method of treatment. Your personalized program will also include exercises that you will do at home, such as stretching, agility exercises, balance activities, and strengthening designed to return you to your former level of pain free participation in sports and other activities.