Quad/hip pain -- any ideas on the cause?

Asking this for a friend who has recently started to experience sharp pain in her leg -- upper part of the quad, below the hip joint, on the outside. Hurts when walking on flat ground or down hill. Does not hurt when walking up hill. Also does not hurt when sitting or squatting. In fact squatting or pulling the knee up toward the chest alleviates the pain.

Does this sound familiar to anyone? Any ideas on what the cause might be?

It started after treatment by a PT for a muscle spasm in the lower back. The PT also found unrelated tightness in the lower quad on the outside above the knee and treated it with ultrasound and massage which left the lower part of the leg a bit sore. The next day my friend spent 3+ hours traveling, had a leg cramp when she arrived at her destination but was able to carry a heavy pack up a steep hill without any pain. This upper/outer quad pain began sometime after that, and it was very painful when the time came to walk back down the steep hill. It's an intense pain deep in the muscle when putting weight on the leg, especially when walking down hill.

My friend is currently traveling in another country, the type of travel that requires long bus and truck rides between remote towns where medical care is not always accessible. So lots of sitting for long periods of time. Also carrying heavy bags.

Any ideas or suggestions are appreciated!!

Hope your friend is ok now! I had something similar, back in 2011 when I tore quad and hamstring in the same leg (different activities in the same week). The upper/outer quad pain was my bodies reaction to the tears where everything tightened up.