Knee joint

Describe the knee joint. This answer should include: the bones involved, the movements and muscles involved, the ligaments involved, any further structures involved, the blood supply and nerve supply of the joint. All attachments should be mentioned. Also include the relations of the joint. (50 marks)

The knee joint is a synovial hinge joint and involves the articulations between the femur and the tibia. The articular surfaces involved include the medial and lateral epicondyles of the femur and their corresponding condyles of the tibia. This type of joint allows flexion and extension of the leg at the knee joint but limited lateral and medial rotation is also provided. The muscles that provide flexion are mainly the hamstring muscles, whilst extension is provided by the quadraceps femoris muscles and sartorius. Medial rotation is largely provided by gracilis, semitendonosus, and sartorius whilst lateral rotation is provided by biceps femoris.

The stability of the joint is provided by the ligaments and tendons that cross the joint, also by the muscles that cross the joint. The meniscus also provide some stability by deepening the articular surface but this is largely insignificant. There are a number of ligaments involved in the knee joint. These can be classified as Extracapsular or intracapsular ligaments. Firstly, the Extracapsular ligaments involved are the: oblique popliteal ligament, acruate popliteal ligament, patellar ligament, medial and lateral collateral ligaments. The patellar ligament is an extension of the common tendon of the quadraceps femoris muscles and extends proximally from the common tendon and attaches distally to the tibial tuberosity of the tibia. The medial collateral ligament arises from the medial epicondyle of the femur and transcends downwards with its deep aspect attached to the medial meniscus and distally attaches to the upper subcutaneous surface of the tibia. The lateral collateral ligament arises from the lateral epicondyle and attaches distally at the styloid process and head of the fibula but does not attach to the lateral meniscus due to the presence of the popliteus tendon. The intracapsular ligaments involved are the traverse ligament of the knee, posterior meniscofemoral ligament, anterior and posterior cruciate ligaments. The traverse ligament of the knee connects the two menisci together whereas the latter connects the posterior cruciate ligament to the lateral meniscus. The anterior and posterior cruciate ligaments are present in order to stop anterior and posterior displacement of the tibia. The former travels upwards backwards and laterally to attach to the lateral epicondyle of the femur whilst the latter rises upwards forwards and medially to attach to the medial epicondyle of the femur.

There are two menisci at this joint, and these are made of fibrocartilage and their function is to provide stability to the joint but deepening the articular surfaces of the joint. The synovial membrane does not include these menisci nor does it include the anterior and posterior cruciate ligaments. There are a number of bursa found at this joint namely: suprapatellar, infrapatellar and prepatellar. The suprapatellar is located just above the patella bone and get swollen in case of injury to the knee joint. Joint fluid can be injected out from this bursa.

The blood supply to this joint is supplied by the genicular artery arising from the popliteal artery and also the anastomosis formed by the femoral, anterior and posterior tibial, lateral circumflex femoral artery. According to Hiltons Law, the nerves supply muscles that cross a joint also innervates that joint. In this case. That means the femoral, obturator, tibial and common peroneal nerves supply these joints. The relations of this joint is as follow; anteriorly we have the prepatellar and superficial infrapatellar bursa, posteriorly we have the contents of the popliteal fossa, medially we have the tendons of gracilis, semitendonosus and sartorius and laterally we have the iliotibial tract and biceps femoris.

Major Points: The type of joint it is?  Bones involved  Articulation surfaces involved  Movements possible  Muscles contributing to the movements possible  Stability of the joint  Ligaments involved  Extracapsular and Intracapsular ligaments  Their appropriate attachments  Meniscus  Synovial Membrane  Bursa present  Clinical significance  Blood supply to the joint  Innervation of the joint + Hiltons Law  Relations of the joint

Remember the hip joint! What are the major points there, do you remember. Well here it is:

Major Points: Type of joint  bones involved  articulations involved  Movements possible  muscles that contribute to these movements  Acetabular Labrum  Significance  Extracapsular Thickenings  Ligament involved  Intracapsular Ligament  Major functions of these ligaments  Relations of the hip joint  Blood Supply of the hip joint  Nerve supply of the hip joint.

Category: Anatomy Notes