Scott Sherman from Panther Sports Medicine answers this question...
Typically, most individuals knees begin to make some noises at some point in their lives. Truth is that most of our bodies tissues are made up of fluid and water. This is particularly so of cartilage that covers the ends of the articulating surfaces of bones that make up our joints. When cartilage begins to lose its water content, it dries out somewhat and becomes less flexible and smooth. With movement occurring over the drier less smooth surface, noises begin to emerge.
In the case of the knees, it is usually the patello-femoral joints that are responsible for all the cracking and popping. In some who develop significant osteoarthritis, we may also begin to notice similar sounds arising from the main knee joint -- the tibiofemoral joint. Medically, these noises are referred to as "crepitus." Many people have crepitus all their lives without any other adverse symptoms, whereas in others, it may be the first sign of degenerative changes.
Supplements like glucosamine, chondroitin, keratin, are hydrophilic compounds naturally found in our cartilage and soft tissues. Hydrophilic means they attract and bind water molecules to keep our soft tissues supple and functioning properly. Taking these orally is theorized to improve the water retention ability of our joint cartilage and thus improve the longevity of our joints and potentially stave off arthritis.
Clinically, the jury is still out on whether these compounds taken orally actually make their way to the affected joints. Some of these molecules are too large to pass through the wall of the gut and are therefore, never even absorbed. My advice to patients is to go ahead and try them for a 3 month period and then see what changes.
Crepitus in knees particularly can also be the result of a flexibility or strength imbalance in the lower extremity. Most of us have heard of the IT band? The iliotibial Band (IT) is a very large, strong, sinewy tendon running along the outside of our thigh terminating at an attachment side on the upper end of the tibia. It is the main attachment for our gluteal musculature and has contributing attachments from the quads and to the patella (knee cap).
If any of the muscles attaching onto the IT band get too tight, this can result in the patella being pulled more laterally resulting in crepitus at this joint. The gluteals often become hypertonic (tight) as a result of lumbar spine dysfunction even though there may not be any overt signs or symptoms here.
Finally, crepitus at the knees often results from sub-optimal foot mechanics. If the foot overpronates (pes planus) or is too rigid (pes cavus), then this can also affect the rotation of the whole lower limb with weight-bearing activities. This alteration can then influence how the patella moves and crepitus is often a sign.
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