While there are many unavoidable risk factors — such as age and gender — for the development of osteoarthritis of the knees, squatting is one activity that people can avoid, and in doing so, lower their risk for developing arthritis later in life.Many studies have found that frequent squatting or kneeling for periods of time can have a deleterious affect on the knee joints as people age. The observations have been made on men and women in occupational settings and in elite and professional athletes.
The act of squatting increases the patella-femoral contact pressures, which is the contact between the knee cap and the thigh bone.
"The patella-femoral contact pressures go up way too high, which crushes the cartilage," said Dr. Daniel Zelazny, a Sports Medicine and Othopaedic Trauma surgeon at Westchester Medical Center in Valhalla, NY.
The pressure on the cartilage in the knee generated by squatting causes a focal area of cartilage cell death, explained Dr. Zelazny. Eventually, that area "flakes off" and the patient ends up with what he described as a "pothole" on the knee.
As the cartilage is lost, the joint space between the bones narrows and the cartilage becomes thinner. The surrounding bones react by growing thicker and growing outward forming bone spurs. When the cartilage is gone, the thickened bone ends rub against each other causing pain with everyday movement.
The American Academy of Orthopaedic Surgeons reports that repetitive stress injuries, due to certain occupational activities, are a major risk factor for developing osteoarthritis. Those activities, according to the AAOS, involve kneeling or squatting, walking more than 2 miles a day, or lifting at least 55 pounds regularly. In addition, the AAOS reports that occupations such as assembly line work, typing at a computer or keyboard, shipyard or dock workers, miners and carpet or floor layers, and performing artists have shown a higher incidence of osteoarthritis of the knee.
In one study, the risk of degenerative lesions was almost 4 times greater for employees in England who reported regular occupational kneeling. The risk due to squatting showed a similar tendency. The study was published in the Journal of Rheumatology in March of 2002.
In another study published in Arthritis and Rheumatism in July of 2000, employees in England who spent more than 1 hour of their workday for longer than a year, involved in activities consisting of prolonged squatting or kneeling, had nearly double the risk of developing arthritis compared to similar people who did little squatting or kneeling. The people whose work involved both heavy lifting and kneeling or squatting had a 3-fold increase in risk.
In the same study, the addition of obesity to squatting and kneeling had a multiplicative effect. Employees with a body mass index of 30 or greater had more than a 14 times greater risk of developing osteoarthritis of the knees.
For those who don’t work in jobs that require regular squatting or kneeling, but instead participate in exercise or sporting activities that require squatting, the risk is still significant. Dr. Zelazny says squatting with weights puts a tremendous amount of stress on the knees. And he suggests only bending the knees to a 30-degree angle. The same goes for the leg press or thigh muscle extension machines at the gym. Again, he suggests only lifting or bending the knees to about 30-degrees.
And finally, new research published in the current issue of the journal Knee suggests one doesn’t even have to be working or exercising to injure their knees. In a study of more than 1200 patients, squatting or ascent from the squatted position, accounted for roughly half of the meniscal tears that occurred during "everyday living" activities. Damage to the meniscus — cartilage that connects the thighbone and shinbone in the knee — has been shown to lead to arthritis later in life.
