It looks like I have Patella Femoral Syndrome. I thought this overview of the problem was pretty good.
Typically patients will complain of localized anterior knee pain which is exacerbated by sports, walking, stair climbing, or sitting for a long time, often called the “Theater Sign” or “Movie-Goers Sign.” The pain from prolonged sitting is thought to occur because of the constant pull of the quadriceps muscle on the knee cap while sitting, which causes its impaction against the hard and unyielding surfaces of the bones of knee joint. Descending stairs may be worse than ascending. Unless there is an underlying pathology in the knee, swelling is usually mild to nil.
Causes
Patella femoral pain syndrome may be caused by overuse, injury, excess weight, a kneecap that is not properly aligned (patellar tracking disorder), or changes under the kneecap.
My physical therapist says my knee cap is not correctly aligned. I will have to do physical therapy twice a week and have 4 home exercises to do.
Exercises
Straight Leg Raise – Straight leg raising exercises help develop muscles of your lower body, including your hips, glutes and thighs.
Sit on the floor with your injured leg straight and the other leg bent with foot flat on floor. Pull the toes of your injured leg towards you while tightening the muscles on top of your thigh. Raise your leg 6 inches off the floor. Hold for 5 seconds and slowly lower your leg. Repeat this 5 times.
Band Resisted Clam shell – The band resisted clam shell exercise is great for strengthening and mobilizing the external hip rotators.
Side Leg Lifts – Side leg lifts work the abs, especially the hard to get at obliques, as well as the inner thigh.
Lie on your side with your legs stacked and your head resting on your arm. Tighten the muscle in the front of the top thigh and lift that leg into the air. Hold for one count, lower to touch the bottom leg and then lift again.
Wall Squat with Yoga Block – The quadriceps, or front of thigh, are the targeted muscles during this exercise but many other muscles get a workout also. The butt, hip, calf, back of thigh, low back, abs, and side abs are all used during this move.
Standing, place an exercise ball against a wall and align it in the small of your back. Position your feet a step, to a step and a half in front of your body such that when you squat down your knees will not protrude past your toes. Place a yoga block between your knees and squeeze. Hold yourself in this position while actively squeezing the block between your thighs. Maintain the pose as long as you can, allowing yourself to come in and out of the pose when you have to, working your way up to being able to hold the position for 1-2 minutes.