Bone and Joint Doc

Informing patients and professionals

The Hip

ANATOMY OF THE HIP JOINT:

Hip anatomy video

To understand all the different conditions that may affect the hip, it is important to have a basic understanding of the anatomy of the hip.
The joint is made up of several structures, which are the following:

Bones
Tendons & ligaments
Muscles
Nerves
Blood vessels
Bursae

Bones:
The hip is a true ball & socket joint & the two main bones involved is the thighbone, also known as the femur & the pelvis bone.  The part of the femur that plays a role in the hip joint, is made up of three parts, namely the shaft (long midsection), the head (ball shaped end) & the neck (straight section that connects the shaft & the head.)  Near the head two bony protrusions can be found, known as the greater & the lesser trochanters (lesser on the inside & greater on the outside.) Their function is to anchor muscle attachments.
The femur head fits snugly into a hollowed out area/socket in the pelvis bone known as the acetabulum.  The pelvis consists out of two large bones, which are connected to each other in the front by a cartilage disc (the pubic symphysis) & at the back by the sacrum.  Four fused vertebrae make up the sacrum & this is actually part of the spine.  On either side of the sacrum, two joints connects it to the pelvis bones.  These joints are the sacroiliac joints.
All the bony surfaces make contact with each other, therefore the dome of the femur head, as well as the socket of the acetabulum is covered with a smooth, rubber like substance called cartilage.  The function of the cartilage is to absorb shock in the joint as well as to aid in smooth movement of the joint.

Tendons & ligaments:
(Tendons = anchors of muscles to the bones & ligaments = soft tissue structures that connect bones to bones.)
First of all, the entire joint is surrounded by a capsule.  The capsule is a thick ligamentous structure with many horizontal & longitudinal fibers & it is lined with a very special membrane, called the synovial membrane.  This membrane secretes a fluid like substance of which the function is two-part.  Firstly it provides nourishment to all the structures of the joint & secondly, it acts as a lubricant to aid in smooth movement of the joint.

The ligaments that play a role are as follows:
Iliofemoral ligament – Lies in the front of the joint & connects the pelvis to the femur.  It has a Y shape & prevents the hip from overextending.

Pubofemoral ligament – Connects the femur to the foremost part of the pelvis, known as the pubis

Ischiofemoral ligament – Strengthens the back of the joint

Besides the capsule & the ligaments, another structure aids in stabilizing & strengthening the joint.  This structure is known as the labrum.  It is a circular ring of cartilage that is attached to the outer surface of the acetabulum, creating a deeper socket for the femur head.

Other ligaments that play a role:
Ligamentum teres – Connects the tip of the femur head to the acetabulum.  This ligament plays no role in the stabilization of the joint, but does contain an important artery that supplies blood to the cap of the femoral head.

Iliotibial band – a long tendon band that runs from the hip to the knee.  Several hip muscles connect here.

Muscles:
At the back of the hip, you will find the gluteal muscles.  They are a group of three muscles nl. gluteus maximus,  medius &  minimus.  They all attach to the back of the big flat part of the pelvis bone & connects it to the greater trochanter of the femur (see above) Their functions are as follows:  Medius & minimus – lifts leg up & out (abducts it) as well as rotates it inwards.  Maximus – extends hip & rotates leg outwards.

On the groin side of the hip, you will find three main muscles collectively called the adductor muscles.  They connect the pubis with the inside of the thigh & their function of is to pull the leg inwards towards the other leg therefore adduct the leg.

The quadriceps & the Iliopsoas muscle can be found at the front of the hip.  The Iliopsoas attaches to the lower spine, as well as to the inside of the pelvis bone & then implants on the lesser trochanter of the femur (see above.)  There are four quadriceps muscles  – Vastus lateralis, – medialis, – intermedius & Rectus femoris.  Only Rectus femoris attaches to the pelvis, the others attach to the femur below the joint.  All these muscles plant into the large bone in the lower leg, the tibia.  Because Rectus femoris is the only one that crosses the hip joint, it is the only one, together with Iliopsoas, that is responsible for flexing the joint.

The muscles that extend the hip, are the hamstrings & they are situated at the back of the hip, connecting the pelvis with the knee.

There are also a number of smaller muscles going from the pelvis to the hip, which helps to stabilize & rotate the hip.

Nerves:
Nerves carry signals to & from the brain.  They tell the hip what the brain wants it to do & the brain how the hip feels.  All the nerves that go to the thigh passes through the hip joint.  In the front, you have the femoral nerve & in the back the sciatic nerve.  A smaller nerve, called the obturator nerve also goes to the hip.
Blood vessels:
In the body, the blood vessels (arteries & veins) usually run alongside the nerves, as is the case in the leg.  The large femoral artery runs alongside the femoral nerve & passes from the pelvis to the leg through the hip area.  It is actually a branch of this artery, the profunda femoris that supplies the hip joint itself.  Two branches stemming from the profunda femoris pierces the joint capsule & supplies blood to the femoral head.  As mentioned before, the ligamentum teres also contains a small bloodvessel that supplies the femoral head.

Bursae:
What is a bursa?  A Bursa is a fluid-filled sack that can be found anywhere between bones, tendons & muscles, where movement causes friction between these surfaces.  The function of the bursa, is to lubricate the surfaces so that smooth movement can take place.  In the hip there are three prominent bursae namely:

Trochanteric bursa – between the greater trochanter & overlying muscles & tendons.  Presents with pain over the outer bump of the hip

Iliopsoas bursa – between iliopsoas muscle & where it passes in front of the hip.

Ilioischial -over the ischial tuberosity – your “sitting bone”

HIP PAIN

Causes:

There are many conditions that can cause hip pain. Hip pain is just a symptom of an underlying problem & it is important to go find out what that problem is.  In order to treat your pain, the underlying problem needs to be addressed.  A problem originating in the joint itself, or in any of the surrounding structures can cause hip pain.

Common causes of hip pain are the following:

  • Arthritis of the hip (especially osteoarthritis)

This occurs when the cartilage in the joint it self gets damaged for some reason or another.  You also get different types of arthritis, where the hip involvement is actually part of a disease that affects the whole body e.g. Rheumatoid arthritis, seronegative arthritises & gout.

  • General joint inflammation: secondary to an infection affecting the joints as well as other parts of the body e.g. flu/food poisoning/tick bite fever etc.
  • Hip fracture – more common in older people or over-active young people
  • Septic arthritis – infection in the hip joint
  • Trochanteric bursitis – a very common condition, where you get pain over the outside of the hip joint, because of inflammation in the overlying bursa. A Bursa is a pouch-like structure, containing a little bit of fluid, which aids in lubricating the muscles moving over the hip joint for smoother hip movement.
  • Tendonitis – descriptive term for any inflammation (regardless of causes) involving any of the tendons around the hip joint.
  • Osteonecrosis

Bone cells need adequate blood supply to survive.  When the blood supply is compromised for one reason or another, the cells will become deprived of oxygen & they will die.  This can lead to bone collapse.  The hip is one of the most common joints affected by this

  • Lumbar spine pathology

A great number of back problems can present with pain in the area of the hip & the buttocks.  This is called referred pain & you would need your dr. to diagnose this. The most common back problems that cause hip pain, are spinal stenosis & disc prolaps.

  • Snapping hip syndrome – collective name for one of three conditions, where either a tendon or the iliotibial band (a band of connective tissue that stretches from the crest of the pelvis to the outside of the knee) “snaps” over one of the bony protrusions of the thigh-bone or where there is a tear in one of the cartilage components of the hip & creates a snapping sensation.
  • Muscle strain, ligament sprains & contusions – Injury to any muscle or ligament in the hip area especially hamstring strains.
  • Stress fracture – a thin hairline crack in the thigh bone secondary to high-impact, high intensity training e.g. long distance runners.
  • Piriformis syndrome – one of the muscles in the buttock area irritates the big nerve (sciatic nerve), which supplies the leg.
  • Non – orthopedic problems:
    • Hernias – bowel protrudes through a weakness in the muscles of the abdominal wall (another cause of referred pain.)
    • Nerve inflammation with referred pain e.g. diabetes & pregnancy.
    • Fibromyalgia – a systemic pain syndrome
  • Childhood problems = all of the above + the following:
    • Developmental dysplasia – The baby is born with its hips dislocated, or not in exactly the correct position.  As a result the hip doesn’t develop properly & can cause arthritis & hip pain at a later stage.
    • Legg-Calve-Perthes Disease – basically the same condition as osteonecrosis described above, but in children.
    • Slipped capital femoral epiphysis – a condition where a part of the head of the thigh bone (femur) slips out of place.
    • Juvenile Rheumatoid arthritis – the body’s immune system attacks its own joints.

When do I need to see my doctor?:

If you have any symptoms that you are concerned about, or makes you uncomfortable, it is always wise to rather seek professional help, than to ignore it. With hip pain, it is especially recommended when you experience one of the following:

  • Difficulty walking
  • Limping
  • Pain that wakes you at night
  • Pain that is getting progressively worse
  • Inability to move your hip
  • If there is any swelling or deformity around the hip
  • If you have a high temperature in conjunction with the pain
  • Any other symptoms that you are concerned about

It is very important to remember, that you cannot just treat the pain!  You need to find out what the underlying cause is & that condition needs to be treated specifically.

As you can see, the hip is a rather complicated & strong joint.  Big bones, muscles & tendons form the main structures & others such as the cartilage & bursae aid in smooth movement.  The hip joins the trunk with the lower limb & its normal function is vital for actions such as walking &running etc.

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