Hamstring strain: This is the most common injury to the hamstring muscles, typically occurring during sprinting, jumping, or sudden stops. It is characterized by pain, swelling, and bruising in the posterior thigh.

Quadriceps strain: Although less common than hamstring strains, quadriceps strains can occur and present with similar symptoms, including pain and swelling, but located in the anterior thigh.
Hip flexor strain: Strains to the hip flexor muscles can mimic hamstring strains, especially if the pain is referred to the posterior thigh.
Calf strain: While less likely, calf strains can cause pain in the lower leg that may be mistaken for hamstring strain symptoms.
Piriformis syndrome: This condition, where the piriformis muscle irritates the sciatic nerve, can cause pain in the buttocks and posterior thigh, similar to a hamstring strain.

Acute compartment syndrome: A medical emergency that can occur after a muscle strain, characterized by severe pain, swelling, and decreased circulation to the affected limb.
Stress fracture: A fracture that occurs due to repetitive stress on a bone, which can present with pain and swelling similar to a muscle strain.
Deep vein thrombosis (DVT): A blood clot in the deep veins of the leg, which can cause pain, swelling, and warmth in the affected limb.

Tendinosis or tendonitis of the hamstring: Chronic conditions characterized by degeneration or inflammation of the hamstring tendons, which can cause persistent pain and stiffness.
Hamstring tendon rupture: A rare but serious injury where the hamstring tendon completely tears, requiring prompt medical attention.
Neurogenic causes: Such as peripheral neuropathy or radiculopathy, which can cause pain, numbness, or weakness in the posterior thigh and leg.