The hip and the knee compose an important part of the lower extremity. While constructed differently, they are interrelated and dysfunction in one can affect the other. The hip and the knee provide a stable foundation that allows the upper body and the trunk to perform activity. Since humans interact with their surroundings through bipedal locomotion, limitations in either of these regions can be devastating.

The hip's strong, bony stability helps protect it from injury. It is one of the body's two ball-and-socket joints, and it is one of the largest and most stable joints in the body. During locomotion, however, the hip can be subjected to forces that are four to seven times the body's weight, thus making the joint vulnerable to stress-related injuries (Anderson et al., 2000). While injuries to the hip are not as common as injuries to the lower extremities, the overall prevalence of hip pain in adults has increased over time (Paluska, 2005). Yet 30% of hip-related pain still remains without a clear etiology.

There are three reasons why it is difficult to determine the origin of hip pain:

1. The joint is not superficial. Pain may be felt across a broader region, making it more difficult to determine which structures are involved.

2. Hip pain is often referred from the surrounding structures, and dysfunction in the sacrum, the lumbar spine, and the groin can all refer pain into the hip.

Not surprisingly, the prevalence of hip pain depends largely on the assessment methods used, and, unfortunately, no gold standard of assessment exists.

Quite different from the hip, the knee is prone to traumatic injury because of its anatomy. It is located at the ends of the two longest bones in the body, the femur and tibia, which act as two long lever arms, exposing the joint to large torques. Because these two long bones are stacked on one another, the knee has to rely on soft tissue structures, such as ligaments and muscles, to provide stability. This intricate balance between static and dynamic structures makes the knee a complicated area to assess. All the relevant structures must be considered, including related areas that may refer pain into the knee, such as the lumbar spine, hip, and ankle.

Entire texts are written on the pathology of the hip and knee. While this chapter is not a comprehensive review of these regions, it does provide a thorough assessment of the dysfunctions and some of the more common pathologies in the regions. In addition, this chapter covers:

• Specific bony landmarks for palpation

• Soft tissue structures, including the muscles of the region

• The movements of the region, and basic biomechanics of the hip and knee

• Manual muscle tests for the hip and knee

• Dermatome and trigger-point referral patterns for the involved muscles

• Some common causes of dysfunction, and how to assess and treat them using soft tissue therapy