A hard lump on the leg may be caused by folliculitis, itchy nodular rash, erythema nodosum or various cysts or lipomas. 1. Folliculitis: If you suffer from folliculitis, scar tissue may appear during the recovery process of folliculitis and may eventually develop into hard bumps, which usually do not need to worry too much. 2. Nodular itchy rash: mostly related to mosquito bites, psycho-neurological factors, endocrine dysfunction and other factors, there will be itching and rash, after repeated scratching to form nodular rash, itching is intense. 3. Erythema nodosum: If the bumps are of different sizes, hard texture and obvious pain when touching, it may be caused by erythema nodosum. 4. Cysts: common in sebaceous cysts, mostly related to sebaceous gland duct blockage, sebum excretion obstacle retention formation of cystic swelling, may also be manifested as a hard lump on the legs. 5. Lipoma: due to the accumulation of mature adipose tissue in the subcutaneous tissues of the legs, will also be manifested as a long hard lump. If you have a hard lump on your leg, you can go to the hospital in time and get targeted treatment after the cause is clear.