Causes of pain in the back of the knee include hamstring injuries, Baker's cysts or posterior cruciate ligament injuries. Hamstring and PCL injuries tend to occur more often in athletes who are runners or play sports, such as basketball, soccer and football. A Baker's or popliteal cyst can be caused by either different types of arthritis or a cartilage tear, states Mayo Clinic.
A hamstring injury can occur if one of the hamstring muscles, which are located at the back of the thigh, is strained or pulled. This can cause symptoms such as sharp pain, bruising, inflammation, tenderness and difficulty walking. If the hamstring strain occurs near the knee, surgery may repair the damage, states MedlinePlus. There are three grades of hamstring injuries. Grade 3 is the most serious and can involve a torn hamstring muscle.
A Baker's cyst develops when the knee produces too much synovial fluid, leading to the formation of a cyst at the back of the knee. The cyst can cause pain and difficulty in bending the knee and may be treated by draining the fluid from the knee, states Mayo Clinic.
The posterior cruciate ligament joins the tibia and the femur at the back of the knee, and an injury to this ligament can be caused by a movement that either overextends or twists it. Depending on the extent of the injury, which can range from a sprain to a torn ligament, the symptoms may include knee pain and inflammation. The back of the knee may also be tender, states Healthline.