Hamstring Anatomy

The hamstring muscles are located on the back of your thigh. They work closely with your quadriceps muscles (front of your thigh), your gluteal muscles, and your calf muscles to ensure proper movement of your leg and hip. They allow your knee to bend, and your thigh to straighten and extend the leg back at the hip. Your hamstring muscles act as a brake to stop an action. You can feel this when walking or running downhill, landing from jumps or performing squats, and when trying to stop quickly after sprinting.

The hamstrings are made up of 3 long muscles that start at the bottom of your pelvis extending down the back of your thigh and along either side of your knee, to your shin bones. The lateral hamstring is the biceps femoris and the medial hamstrings are the semitendinosus and the semimembranosus. The tendons (tough fibers that connect muscle to bone) for these muscles begin at your ischial tuberosity (the bony bump under each buttock, known as your "sit bones") and attach on the outer edges of your shinbone (your tibia and fibula) just below the back of your knee. They help to stabilize your knee. Your hamstrings also have a lot of soft connective tissues and are innervated by your sciatic nerve. This part of your body is prone to injury because it crosses 2 major joints - your hip and your knee.

Hamstring Tendonitis

Hamstring tendonitis is often confused with hamstring tendinopathy or tendinosis. Hamstring tendonitis refers to inflammation (pain, swelling, warmth, redness and dysfunction) in one or more of the hamstring tendons located around the ischial tuberosity and/or just below the knee (on tibia and fibula). Hamstring tendinitis often leads to hamstring tendinosis (tendinopathy) over the long term.

Hamstring tendinopathy (or high hamstring tendinopathy) is a chronic tendon injury that involves degeneration of the hamstring tendons at their attachment to the ischial tuberosity or the shinbones (just below the knee). This type of tendinosis is a result of excessive tension, effort and/or repetitive use of your hamstring muscles and tendons. The initial damage can range from overstretching to partial tearing to complete rupturing of the small fibers that make up your hamstring muscles and tendons. If you do not allow your tissues to heal properly, your previous hamstring injuries will build upon each other. The inability of your tendon to repair itself encourages the microtears to accumulate faster than they can heal, increasing the degeneration in your tissue and reinforcing your pain and disability.

If you have hamstring tendinopathy or tendinosis damage happens at a cellular level - your tendon (which is made up of collagen fibers) becomes weaker and thinner over time and the hamstring tendon fibers begin to fray and separate. The tendon looses its glistening appearance and elasticity, and often changes to a soft texture that is yellow or brown in color (mucus-like appearance). Scar tissue (very fibrous tissue that develops in the healing of wounds) or calcific deposits (calcium phosphate) develop around the injured area which can decrease the blood supply to the tissue.

This condition can be in one or both of your legs and normally affects active people between 30 - 50 years old, especially distance runners, sprinters, tennis players, skaters, and soccer players (or those who participate in team sports with lots of running). Other conditions that are often seen with hamstring tendonitis are bursitis, rheumatoid arthritis or diabetes, avulsion fractures, stress fractures, and/or referred back pain.