Lateral Hip Pain is a common condition and goes by a number of different names such as:
Greater Trochanteric Pain Syndrome
The pain generally arises from the gluteal tendons that attach to the "bony" area on the side of your hip.
Key symptoms include pain/tenderness over the lateral hip area (the bony area on the side of your hip), and pain with activities that "load" the lateral hip area such as:
Standing on one leg
Going up/down stairs
Lying on your side (often the painful side)
Crossing your legs
Whilst pain may be felt in your lateral hip area it does not necessarily mean that your pain is coming from there. Pain can also be referred/sent to this area from other areas of your body such as your lower back, sacroiliac joint and hip joint.
Effective treatment revolves around strengthening the gluteal muscles (bum muscles),managing your activity levels so that pain is tolerable, and modification of lifestyle factors. Other types of physiotherapy treatment (massage, acupuncture, stretches) and medical procedures (cortisone injections and/or medications) can sometimes provide relief, but it is generally only short term.
Thanks for reading.
Grimaldi A, Mellor R, Hodges P, Bennell K, Wajswelner H, Vicenzino B.Gluteal Tendinopathy: A Review of Mechanisms, Assessment and Management.Sports Med. 2015 Aug;45(8):1107-19.