The hip is composed of two bones, the head of the femur (ball on top of thigh bone) and the acetabulum (socket) that is a portion of the pelvis. The ends of these bones that move about each other have a layer of cartilage, which forms the surface of the joint. There have been multiple studies looking at different risk factors for osteoarthritis in the hip and one of the factors is impingement. This may occur as a result of extra bone placed on either the femoral head (ball) or the acetabular rim (socket).
The term “Cam Impingement” is used to describe extra bone formation in front of and at the superior aspect of the femoral head and neck junction. In this scenario, as the hip is flexed the area of extra bone growth called the “cam deformity” will engage the anterior aspect of the socket. When this happens repetitively, like when one performs squatting or sits for a long period of time, this can cause damage to the cartilage of the socket and the overlying labrum. The labrum is a fibro-cartilaginous lip of tissue that lines the rim of the acetabular socket. The labrum is an important structure involved in joint fluid regulation into and out of the hip socket. When there is a labral tear, or tear in the labrum, there may be an abnormal regulation in this joint fluid that may lead to micro-instability in the hip and thus further increase the risk of cartilage damage. The term “Pincer Impingement” is used to describe the scenario where there is too much bone on the acetabular socket. This may also cause repeated damage to the acetabular labrum and cartilage and also the femoral head cartilage.
Patients may experience improvement in symptoms with a hip steroid injection and potentially physical therapy. There are also minimally invasive arthroscopic hip surgeries, which attempt to remove excess bone that causes impingement and cartilage damage. In this procedure it is also possible to perform a labral repair or debridement. Severe cases may be indicated for a minimally invasive anterior approach total hip replacement surgery or total hip arthroplasty.
Discomfort and pain are described by patients as a dull, aching throb that is deep in the hip. This typically is located in the groin fold in front of the hip and will radiate down the front of the thigh toward the inner aspect of the knee and toward the buttock region. In fact, many patients may have the sensation that their knee hurts; however, it may just be radiating pain from hip joint problems. Many will also describe a sharp, stabbing type of pain that is equilibrated to being “stabbed by an icepick”. Pain can also elicit a feeling of weakness in the muscles around the hip, which can result in the leg buckling or giving way. The pain typically increases whenever the hip joint is bent during activities like squatting, sitting and stairs. Athletic activities such as running and jumping, which require hip flexion, will also aggravate these symptoms. Activities that also require rotation through the hip, such as golf and pickleball may also increase these symptoms.
A person’s range of motion, or movement, of the hip will also be affected. This effectively decreases ones ability to fully bend or straighten the hip. Patients typically have difficulty tying shoes or picking up objects from low-lying places.
In severe cases, a person may be able to feel or hear the hip joint moving and grinding. This may be a result of damaged cartilage and bone moving about each other or perhaps from loose fragments floating in the hip or a flap from a concomitant labrum tear catching on the overlying bone.