Pain in the front of the knee is a common complaint at all ages, especially for women. However, anterior knee pain is not a diagnosis in itself anymore. Most anterior knee pain is related to the patellofemoral joint and its musculature and ligament support. So-called "patellofemoral pain" has become the most common knee symptom in the average orthopedic outpatient clinic. Depending on the exact cause, it is two to seven times more prevalent in women.
It is estimated that up to 10 percent of all aging knee pain is due to isolated patellofemoral arthritis. Because the exact source of pain can be difficult to isolate and is often multifactorial, patellofemoral pain syndrome requires careful diagnosis and proper management to avoid unnecessary, ineffective or potentially harmful treatment.
While the pain of inflammation or muscle soreness may be temporary, pain due to structural damage (e.g., arthritis) can be made worse by ignoring symptoms of pain, swelling, catching and stiffness.
- An accurate, early diagnosis is critical to avoid irreparable damage from improper activity or training.
- Nonoperative solutions only work if accumulative joint damage is not too great.
- Self-diagnosis is rarely successful if pain is severe enough to cause a limp or a change in activity or work behavior.
- Knee pain associated with climbing stairs and squatting is most often due to kneecap problems.
Common Causes of Patellofemoral Pain
Pain in the front of the knee can come from many sources, including:
- Weak or overused muscles
- Kneecap (patella)
- Inflammations and tendon injury (bursitis, tendonitis)
- Loose ligaments with instability of the kneecap
- Articular cartilage damage (chondromalacia patella)
- Swelling due to fluid buildup in the knee joint
- An overload of the extensor mechanism of the knee with or without malalignment of the patella
Sources of Patellofemoral Pain
- Muscular: Excessive muscle tightness (inflexibility), fatigue or tearing (strain) of quadriceps or hamstring muscles, muscular strength imbalances, overuse/disuse
- Structural damage: Chondromalacia patella (chondro = cartilage, malacia = softening, patella = kneecap), patella arthritis, stress fracture, direct traumatic injury
- Congenital dysplasia: Patella alta (high patella), facet or trochlear dysplasia
- Malalignment: Tilted patella, intoeing rotation of the legs (persistent femoral anteversion), knock knee (excessive valgus deformity)
- Instability of the patella: Maltracking with subluxation (partial) or complete dislocation of the kneecap, damaged or stretched ligament support
- Inflammatory: Bursitis, tendonitis
Overuse of muscles
Bending and overuse of the knee leads to high repetitive pressures between the kneecap and the femoral groove. The resulting overload, muscle fatigue and imbalances are the most common source of soreness and weakness around the knee. Who is most vulnerable to this problem?
- Patients who are too aggressive in starting a fitness program
- Young mothers or grandmothers who repeatedly squat to pick up little children
- Workers who must climb
- Runners and athletes who overtrain
Younger patients should be analyzed for inflexibility acquired from rapid teenage growth or poor conditioning. Inactivity can be just as bad as too much activity. Just sitting with your knee bent can cause pain when you get up.
Treatment: The good news is that these conditions can respond well and do not need operative treatment. Beware of exploratory arthroscopic surgery or the suggestion that a "lateral release" may be helpful. Such approaches often lead to worse symptoms if not carefully planned. A quality physical therapy program prescribed by your orthopedic surgeon after proper evaluation is the best place to start. At the Rubin Institute, we teach improved exercise or work behaviors combined with patellofemoral-specific rehabilitation. Braces and orthotics may also be helpful.
Structural damage to the patella or the groove in which it travels (the femoral trochlear groove) can occur from direct injury, such as from a car accident (also called dashboard knee). Such blows can kill the cells in the surface cartilage layer and lead to softening or complete loss of tissue covering the bones. Either the kneecap or the femoral surface, or both, can be affected.
Noisy knees (crepitation) with crunchy sounds during knee bending (e.g., stair climbing, squatting, working out with weights) are one of the first signs of articular damage (chondromalacia and degenerative arthritis). This stage is often misleadingly painless. Pain and swelling develop with time and further overactivity.
Excess weight can often set off these symptoms, which is why women often experience knee pain following pregnancy or menopause. Accumulative overuse (improper fitness or athletic training) combined with aging can also lead to advanced arthritis (wear-out of the joint surface) at a young age (less than 40 years).
Treatment: When caught early, anti-arthritis measures such as weight loss, quad exercises and learning smarter activity habits (like avoiding knee bends, switching to safer exercises), combined with cautious use of medication or injection, can help tremendously. If swelling and limping are severe despite these measures, arthroscopic surgery may help. Arthroscopy:
- Provides a more accurate diagnosis
- Relieves some of the pain of inflammation by washing out the knee
- Quiets down the aggravation of rough joint surfaces and reduces mechanical irritations
- Combined with other surgical measures can realign or stabilize the kneecap
- Removes a painful plica
For complicated cases, patellofemoral realignment and conservative resurfacing (either biological or prosthetic) may be necessary.
Some people are born with misshaped kneecaps, or the groove in which the patella must travel is too shallow. This can lead to abnormal wear or instability. Such conditions may be present in youth, but may not be noticed until adulthood, when aging or excessive activity begins to aggravate the knee.
Treatment: Exercising can help, but if symptoms continue to be disabling, operative treatments can be used to correct the forces on the kneecap. Such operations require the surgeon to have special experience and training.
Malalignments can involve the whole leg or just the kneecap joint (patellofemoral) portion of the knee. Persistent intoeing from birth is often due to internal rotation of the femur bone and contributes to a maladaptation growth pattern known as "malicious malalignment syndrome." This inherited characteristic is often seen in young girls and persists into adult life.
Many patients complain of aching while exercising or playing sports. Others see that their kneecap is tilted or out of position. This can lead to pain from excessive lateral (outer side of knee) patella pressure. In advanced cases the patella begins to wear and deform, causing mechanical symptoms of sharp pain or catching. Sometimes the knee just gives way, resulting in excessive falls. Such instability can be a pseudo phenomenon of pain-induced muscle weakness in the leg. Sometimes the kneecap actually jumps out of place. Recurrent patella dislocation (either partial or complete) is due to loose ligaments, patellofemoral dyplasia or both.
Treatment: Most overuse/overload patellofemoral pain responds initially to nonoperative treatment. In younger patients, treatment always begins with methods such as icing, arch supports, physical therapy, patella support braces, and moderate, short-term anti-inflammatory medication. A taping and rehabilitative program (McConnell) should be tried. True patella dislocations can be managed with arthroscopic surgery, or with more complicated ligament and/or extensor realignment surgery. If arthritis or severe chondromalacia develops and other efforts fail, then patella replacement can be very helpful in both the older and younger patient.
Patella tendonitis results from excessive overload or overuse of the extensor mechanism of the knee. Known as "jumper's knee," this injury occurs not only with the strain of jumping, but also during landing after a jump, excessive weight lifting or kicking. The injury is a true tearing and degeneration of the tendon at the microscopic level with failure to heal (tendinosis). Activities such as basketball, soccer, Tai-Bo, step aerobics and volleyball can produce this injury. Ignoring this pain may lead to a sudden rupture of the patella tendon and eventually to emergency surgical repair.
Treatment: The proper diagnosis is for the patient to undergo an eccentric tendon therapy program, bracing and modified activity. In difficult cases our center has pioneered leading approaches to stimulating the healing of injured tendons. Percutaneous methods in the office, as well as outpatient arthroscopic and surgical tenotomy, are very successful.
Prepatella bursitis is an inflammation of the small lubricating sac under the skin in front of the kneecap. Normally this sac is flat and has a film of fluid that allows the skin over the patella to slide and be protected when kneeling. Excessive kneeling (e.g., wrestling, scrubbing floors, laying carpet) or direct trauma (blunt force from a car accident or fall) can cause increased fluid or bleeding in this sac, resulting in a bump (water on the knee), pain and redness. Infection can follow.
Treatment: Anti-inflammatory medication, removal of fluid and steroid injection can all help. In persistent cases, the sac may need to be removed with minor surgery.
A plica is a normal fold of tissue within the knee that can cause patellofemoral pain symptoms if aggravated by injury or overuse. It is diagnosed by a distinct presence of tenderness along the inside of the kneecap. There is often a popping or catching sensation when bending the knee.
Treatment: Physical therapy, local icing, injection and relative rest most often help. Arthroscopic excision of this functionless structure can be a practical and simple remedy for persistent cases.
To make an appointment with a knee specialist at the Rubin Institute, please call 410-601-WELL.