For many years, I have seen spot softening of the articular cartilage under the patella. This frequently occurred in young people, usually female patients, who had no injuries or other findings. Many got relief by using a knee immobilizer for 6 weeks.
After looking at the activities and demographics of the patients, I felt foolish. I realized most of them were young people at or younger than 30 years of age who were sitting on top of one foot in a chair with the knee hyper flexed under them or were workers who squatted or kneeled a lot without knee pads. These positions placed extreme pressure on a localized area of the patella for a long time, thus depressing and softening the articular cartilage like the foot of a chair does to the carpet. The longer the pressure is present, the more it is depressed. They frequently admitted they could no longer sit on that foot and just switched to the other one.
I tell them not to sit on their foot or hook their feet under the chair. They will need their family members to remind them because it is such a habit. The reason some women sit on their foot is because their feet do not reach the floor and sitting on one foot flattens their back and makes them more comfortable.
They also told me they hurt more walking down stairs or a hill than going up such constructs. However, they could go down the hill backwards without the pain. I realized the reason for this was because the soleus muscle, which flexes the ankle, acts in reverse when the weight is on a flat or dorsiflexed foot. It then pulls the tibia posteriorly, thus extending the knee and taking the pressure off the patella.
Use of a knee immobilizer for 6 weeks allows the softened articular cartilage to rehydrate by taking the pressure off of it and to become firm again.
I have been successful treating these young people with a knee immobilizer or cast for 6 weeks and having them do soleus exercises if the pain is severe. Just changing their habits works in mild cases.
Look around and see how many young women sit like this. If they are active after prolonged sitting or kneeling, the motion across the softened cartilage chews it up like “crab meat.”
Disclosure: Hubler reports no relevant financial disclosures.
David Hubler, MD, has been in solo orthopedic practice in Dallas for 25 years. He has been doing locums for 9 years and has been to New Hampshire, West Virginia, Michigan, Indiana, Louisiana, Texas, Oklahoma, Colorado, Washington, Hawaii, and South Carolina with Ohio as his next stop.