Pain and tenderness over the outer side of the hip joint happens when underlying muscle/tendons rubs excessively over the bony prominence over outer side of the upper thigh.
You will feel the pain going down the leg up to the knee. Lying on the affected side is uncomfortable. There will be pain on pressure.
No investigations are necessary for this problem. Milder forms of the condition can be managed with medication and physiotherapy. Severe cases need injection of medication to the site. it resolves without a problem. It may recur.
A nerve getting trapped at groin can give rise to a similar pain which goes down the outer thigh. The pain may give a burning sensation.
orthopaedic concern of pain at the groin is something to do with your hip joint. Commonest cause will be to have arthritis of the joint. There will be more pain in the mornings in inflammatory type arthritis and osteoarthritis will give you more pain towards the evening and the nights. Over stretching of tendons around the hip may also cause pain at the groin.
Clinical examination could sort out this for you. an ultrasound examination and an x-ray of the hip joint will provide more information.
There will be conditions giving rise to pain over the lower buttock and the pain goes down back of the leg, over the hamstrings up to the knee. you will find it difficult to sit on a hard surface. Bending forward is also difficult. This is technically termed ischeal bursitis. This usually settles with an injection to the site.