You inherit the durability of the articular cartilage – the smooth gliding surface that coats the end of all bones that form a joint. We do not fully understand this lack of durability, but we see a family history of multiple family members that have arthritis in their knees without unusual overuse or injury.
So the “weekend warrior” who has played sports their entire life or participates in sports in their spare time increases their chances of causing wear and tear injuries, especially if this is compounded by genetics, obesity, malalignment and past injuries. The high school athlete that has a major portion of their meniscus excised at age 18 will commonly start seeing some arthritis forming 20-25 years later.
The United States has record high levels of obesity. Obesity increases the stress to the knee joint by a factor of 4-5 times. 50 extra pounds can increase the knee joint forces up to 250 pounds per square inch.
Bow legs (varus) or knock knees (valgus) wear the joints out faster. The normal joint is 50 valgus so it shares the load 50% inside and 50% outside. If the knee is abnormally aligned, this can shift to 60:40 or 70:30 so the abnormal joint receives excessive stress.
Articular Cartilage Damage
The smooth gliding surface of the knee joint can be damaged by multiple small injuries that accumulate through life and sports or significantly damaged by major injuries or fractures. If a fracture (or broken bone) involved the knee joint it can accelerate the arthritics. We call this post traumatic arthritis. Major ligament injuries like ACL tears can also damage articular cartilage.
The meniscus is a C-shaped cartilage spacer that acts as a shock absorber for the knee. You have 2 – one on the medial side (inside) and lateral side (outside) of the knee. When someone has a “cartilage tear” this structure is torn. If it has to be removed by arthroscopic surgery (which is a very common surgery that we perform), the shock absorbing function can be diminished leading to increased wear on the joint.
I will not ever get into inflammatory arthritis (rheumatoid, Lupus, gout psoriatic) or Avascular necrosis – people that have this are not going to be participating in “weekend warrior” activities to a very high degree.
What do you do if you start to develop arthritis?
Planting, pivoting sports like basketball, soccer and long distance running may have to be limited. Golfers may have to ride golf carts instead of walking. Runners may have to shift to activities that are less stressful (Walking, elliptical machines, bicycle, swimming, weight lifting) that avoid stress to the knee joint. If it hurts, don’t do it.
Non-Steroidal Anti-inflammatory medications can be used – Aspirin, Ibuprofen, Aleve and the 20 prescription NSAID’s that are available. They can decrease the inflammation and pain and allow more activity. NSAID’s have side effects so they have to be used carefully with following by your primary care physician. Some potential side effects are stomach irritation (even ulcers), kidney damage, blood thinning and cardiac effects.
Supporting braces can help take the stress off of the knee. This can be as simple as an elastic sleeve or as complex as a valgus loading brace that distributes the joint forces to the “good” side and unloads the arthritic side – these are expensive and somewhat cumbersome to wear but they can be helpful.
Cortisone – the world’s most powerful anti-inflammatory – can be used sparingly to limit pain and inflammation. There are limits to the frequency and extent of their use. Hyaluronic acid (Synvisc, Hyalgan) injections can also be used to improved pain and decrease inflammation.
Outpatient resection of meniscus tears and smoothing of articular cartilage can be performed through 3 “stab” incisions. This dramatically helps pain from meniscus tears but does not predictably help the articular cartilage damage.
If the articular cartilage is damaged to the degree that bone is exposed at the joint surface, this is the beginning of severe arthritis. When all non-surgical treatments have been exhausted and the pain and disability start to greatly limit activities, then artificial joint replacement using metal and high tech plastic can be considered. Basically, the worn surfaces of the joint are removed and replaced with stainless steel surfaces and cross linked polyethylene plastic spacers. Modern total knees are durable and long lasting but they do not allow running and jumping. Once you have a total knee, sports are limited to walking and low stress activities.
Millions of people can enjoy sports their entire life without major damage to their knees. There are also many athletes and “weekend warriors” who participate in competitive and recreational sports that damage their articular cartilage over time and develop arthritis that needs to be treated. Total joints should be considered as a last resort to these athletes but there are still many low impact activities and sports that can be enjoyed by ageless and active people.