BY PAUL THORMAHLEN, MSPT, ACT – Two structures called menisci (plural for meniscus) sit between the femur (thighbone) and the tibia (shinbone). These structures are sometimes referred to as the cartilage of the knee, but the menisci differ from the articular cartilage that covers the surface of the joint.
The menisci enhance the stability of the knee and protect the articular cartilage from excessive concentration of force. They act like a gasket, helping spread out the forces that are transmitted across the joint. Walking puts up to 2x your body weight on the joint. Running puts about 8x your body weight on the knee. Without the menisci, the concentration of force into a small area on the articular cartilage can damage the surface, leading to degeneration over time. In addition to protecting the articular cartilage, the menisci help the ligaments with stability of the knee. The menisci make the knee joint more stable by acting sort of like a wedge that you might set against the bottom of a car tire.
Injuries/Conditions Associated With Meniscus
The meniscus is a commonly injured structure in the knee. The injury can occur at any age. In younger people, the meniscus is fairly tough and rubbery, and tears usually occur as a result of a forceful twisting injury. The meniscus grows weaker with age, and meniscal tears can occur in aging adults as the result of fairly minor injuries, even from the up-and-down motion of squatting. Without the menisci, the forces on the knee joint are concentrated onto a small area, leading to damage and degeneration of the articular cartilage, a condition called osteoarthritis.
Articular Cartilage is a smooth, slippery material covering the ends of the bones that make up the knee joint. The cartilage allows the bones to slide against one another without damage to either surface. This material is about one-quarter of an inch thick in most large joints.
The function of articular cartilage is to absorb shock and provide an extremely smooth surface to facilitate motion. We have articular cartilage essentially everywhere two bony surfaces move against one another. In the knee, articular cartilage covers the ends of the femur, the top of the tibia and the back of the patella.
Injuries/Conditions Associated With Articular Cartilage.
The main problem with articular cartilage occurs with degeneration called osteoarthritis (OA) or arthritis. OA simply is the wearing away of the articular cartilage exposing the sensitive bone underneath. This can be caused by a knee injury earlier in life but not all cases of knee OA are related to a prior injury. It can also come from years of repeated strain on the knee. Also, scientists believe genetics makes some people prone to developing degenerative arthritis. Obesity is linked to knee OA. Losing just 10 pounds can reduce the risk of future knee OA by 50%.
People who modify their activities can actually slow down the effects of knee OA. For instance, people who normally jog might decide to walk, bike or swim to reduce impact on their knee joints. Sports that require jumping and quick starts and stops may need to be altered or discontinued to protect the knee joints. The use of one or a pair of trekking poles during walking or hiking may also help reduce symptoms of OA.
A physical therapist can teach you range-of-motion and stretching exercises that can be used to improve knee motion. You can also be shown strengthening exercises for the hip and knee to help steady the knee and give additional joint protection from shock and stress. People with knee OA who have strong leg muscles have fewer symptoms and prolong the life of their knee joint. Your therapist will also suggest tips for getting your tasks done with less strain on the joint.
A knee unloading brace can help when OA is affecting one side of the knee joint. For example, a bowlegged posture changes the way the knee joint lines up. The inside (medial) part of the knee joint gets pressed together. The brace is designed to share the pressure and unload the arthritic side of the joint. A knee unloading brace can help relieve pain and allow people to do more of their usual activities. Northern Rockies Physical Therapy carries unloader braces and has an experienced staff to help you determine if the use of a brace would be beneficial to you.
Call NRPT today at (406) 543-0617 for more information or to schedule an appointment. We have nine physical therapists and two convenient locations in Missoula to serve all your physical therapy needs.