Lymph circulation is the waste management system of our bodies. It transports waste materials (toxins, dead bacteria and cells, cancer cells, dietary fats from our digestive system, interstitial fluid, etc.) out of our bodies. Lymph travels just under the skin through vessels. It is cleaned in the nodes and eventually returns to the whole blood in the circulatory system. Unlike blood, which has the heart to pump it, the lymph has no pump to keep it flowing. It is entirely dependent on external factors in order to operate optimally. Here are some ways to keep it moving:

pumping action of your gastrocs through walking or running
massage, particularly the light, directional, rhythmic lymph drainage massage
jumping, particulary on a rebounder or trampoline
skin brushing
hydrate
deep breathing
hot & cold treatment
stillingia tincture
Qi machine

It's terribly important not to restrict lymph flow with tight clothing, especially bras. If you wear a bra make sure it's well fitted and doesn't leave long-lasting grooves in your skin when you take it off.

There are oh-so-many ways that the low back and knees are connected. One that has been catching my attention of late is that people who complain of chronic low back pain invariably have grainy, mealy, lumpy, unhealthy soft tissue on the popliteal fossa (backs of the knees). In the middle of the popliteal folds (transverse crease of popliteal fossa, to be precise) is Bladder 40 (UB40, Wei Zhong), a potent acupoint for low back pain. How did the ancient Chinese physicians make this connection? There are many theories and beliefs about how acupuncture came to be. But I wonder if perhaps some physicians, who were more focused on manual modalities and the cadaver studies done at the time, noticed this difference in the tissues and that perhaps this contributed to the discovery of the acupoint.

Tissues reflect the health of the structures with which they are related. Often these are contiguous (next-door or adjacent) structures, but sometimes these structures are related through their fascial connections (like the low back & knees). It is through these fascial connections that tissues can, in turn, influence the health of other organs and structures in the body. It goes both ways. So keeping the tissues healthy through hydration, nutrition, massage, manual therapies, skin brushing, etc is important to overall health of the internal organs.