As the other poster said, it may be DOMS, which is caused by eccentric muscle damage and subsequent immune system response, NOT lactic acid. The key phases of DOMS include the structural damage to the myofilaments and surrounding tissues (leading to increased sensitivity by the myogenic nociceptors to touch and lengthening of the tissues), and the immune system response, where phagocytes destroy the damaged cells (including some healthy ones) and the cells are replaced by structurally stronger cells.
Basically, structural damage, then Ca2+ homeostasis is disrupted, resulting in necrotic cell death, intramuscular contents stimulate the nerve endings (results in pain), activation of the immune system and improper killing of both healthy and damaged tissues, new muscle fibers form to replace muscle damage, and the muscle strength is restored.
Acute soreness occurs approximately within 1-2 days, and DOMS peaks 2-3 days, after which inflammation of the tissues should be down to normal by the seventh day. The inflammation response is biphasic, the first phase (24 hrs) caused by eccentric damage and the second phase (48-72 hrs) by secondary damage of the healthy tissues by the immune system.
"Treatment" of DOMS
NOT Ice, RICE, or anti-inflammatory drugs.
Best treatments: time and rest from activity. Allow your muscles to recuperate and restore the damaged cells!
Try to strengthen and increase the endurance of the hamstring muscle group to help reduce the fatigue of the quadriceps. Also, for the VMO thing (runner's knee?), I would (remember, this is only advice, not a medical or health care professionals recommendation. Consult your physician or PT about this) increase strength by performing more compound resistance exercises that will work out the major muscle groups of the lower extremities, such as the gluteal group (which aides in medial rotation). Exercises such as squats and lunges are fine.
Good luck.
