PROCEDURE

1. PRE-WORK (before lab) review the overall organization of the bony lower extremity (the structures covered in the previous lower limb dissection lab sessions) from your atlas or on an articulated skeleton in the lab.

Pelvis (Netter334) (Netter476).

Femur (Netter479).

Tibia (Netter504).

Fibula (Netter504). 

Foot bones (Netter515) (Netter516) (Netter517).

PROCEDURE - DORSAL FOOT

2. Return to the ankle joint where the vessels, nerves, and tendons of the anterior compartment structures cross into the extensor retinaculum at the dorsum of the foot. 
    (Netter521) (Netter511) (Photo5080) (Photo5081)

From medial to lateral these are the:

- Tibialis anterior tendon
- Anterior tibial artery and vein
- Deep fibular nerve
- Extensor hallucis longus tendon
- Extensor digitorum longus tendon
- Fibularis tertius tendon (often absent)

3. Clear fascia from the dorsum of the foot sufficiently to follow the tendon of the tibialis anterior muscle to the medial side of the foot.
    (Figure534) (Netter521) (Netter511) (Photo5097)

The tendons crossing into the dorsal foot pass underneath the extensor retinaculum. This is a thickening of the crural fascia 'anchoring' the tendons to prevent them bowing out when contracting.

Leave a band of the extensor retinaculum intact when removing fascia over the dorsum of the foot to expose the tendons. This will keep the tendons neatly in relative positions for later study.

The tibialis anterior muscle originates from the lateral upper part of the tibia and attaches to the medial foot (cuneiform and first metatarsal bones).

4. Clear fascia from the dorsum of the foot sufficiently to follow the tendon of the extensor hallucis longus muscle to the base of the great toe.
    (Figure534) (Netter511) (Netter521) (Photo5098)

The extensor hallucis longus muscle arises from the fibula and its tendon attaches to the base of the distal phalanx of the great toe.

Several additional retinaculum bands, the inferior extensor retinaculum, span over the tendons on the dorsal surface of the foot, but these are not always clearly observed. If these are particularly thick, you may need to remove part of this retinaculum to effectively follow the tendons.

5. Clear fascia from the dorsum of the foot sufficiently to follow the tendon of the  extensor digitorum longus across the foot to see it separates into slips to toes 2-5.
    (Figure534) (Netter511) (Netter521) (Photo5099)
    (iPhoto5001)

6. Examine lateral to the extensor digitorum longus tendons on the dorsum of the foot for the tendon of the fibularis tertius muscle connected to the lateral side of the 5th metatarsal bone.
    (Netter510) (Netter520) (Photo5038)

This muscle and tendon are present in only ~60% of individuals. Most of the time, if present on one leg it will be present on the other, but ~20% of the time it will occur only on one leg.

The tendon also exhibits considerable variability in size and extent. The tendon itself may be a prominent tendon, a slip of tendon separating from the extensor digitorum longus tendon, or absent completely.

If the fibularis tertius tendon is present, follow it proximally and observe the size of the muscle. The muscle can be a distinct entity or fused into the extensor digitorum longus muscle.

7. On the dorsum of the foot, dissect into the space between the extensor hallucis longus tendon and the extensor digitorum longus tendon of the 2nd digit for the tendon of the extensor hallucis brevis.
    (Figure536) (Netter511) (Netter521) (Photo5100)

In this space will be the obliquely directed tendon of extensor hallucis brevis attached to the big toe.

8. Follow the tendon of extensor hallucis brevis proximally to see part of the muscle belly situated deep to the tendons of extensor digitorum longus.
    (Figure536) (Netter511) (Netter521) (Photo5100)

Extensor hallucis brevis is essentially the medial part of the extensor digitorum brevis muscle and most likely is not a distinctly separate muscle belly.

9. Dissect into the spaces between the other extensor digitorum longus tendons as they pass to the digits, where you will find the small, obliquely directed tendons of the extensor digitorum brevis.
    (Figure536) (Netter511) (Netter521) (Photo5100)
    (iPhoto5001)

Extensor digitorum brevis tendons insert into the lateral sides of the extensor digitorum longus tendons going to digits 2-4. 

10. Dissect one of the extensor digitorum brevis tendons proximally to the muscle belly situated deep to the tendons of extensor digitorum longus.
    (Figure536) (Netter521) (Photo5038)

PROCEDURE - THE HIP

The following procedure to be performed on one leg only. As this procedure can be disruptive of structures in the anterior thigh, select the leg with the best preserved structures and carry out the following steps on the other leg only.  

11. The hip joint is a multi-axis ball and socket between the femur and the pelvis. 

The depth of the hip socket, its stout capsular ligaments, and surrounding muscles afford the joint great stability and strength, yet still allow a wide range of motion.

12. Transect the  tensor fasciae latae muscle close to the origin at the anterior superior iliac spine.
    (Figure541)

13. Retract the femoral nerve/artery medially.

14. Transect the sartorius and rectus femoris muscles close to the origin at the anterior superior and inferior iliac spines so that they can be reflected distally.
    (Netter482)

There can be considerable fascia limiting your ability to  reflect these muscles. If that is the case you may need to cut below, parallel, or even through this fascia.

This exposes the anterior surface of the hip joint which is directly deep to the sartorius, rectus femoris, and tensor fasciae latae muscles.

This anterior approach is preferred surgically as there are fewer muscles anterior to the hip joint and the surgeon can work between the muscles often reducing muscle disruption compared to a posterior or lateral hip approach.

15. Press fingers against the anterior hip joint and move the donor's leg such that you can feel the movement of the femur relative to the pelvis underneath the joint capsule and surrounding ligaments.

The hip joint ligaments are named based on the bones they span; iliofemoral (ilium to femur), pubofemoral (pubis to femur), and ischiofemoral (ischium to femur). The existence of separate names implies they are well defined, but in reality they are closer to a continuous spiral of strong collagen fibers that are not readily discernable as having separate bony origins. (Figure542) (Figure543) (Netter477)

As the hip ligaments fuse tightly to the capsule, it is typically impossible to see the capsule as a separate structure. The capsule completely encloses the ball-and-socket joint made by the head of the femur and extends inferiorly to the base of the neck of the femur.

Hip fractures are classified as intracapsular (involving the head and/or neck of the femur with high risk to the vascular supply of the head) or extracapsular (involving the trochanters or sub-trochanter area with lower risk to vascular supply).

16. With a scalpel, slice through the anterior side of the capsule exposing the interior of the joint.
    (Figure544)

Commonly this incision is made too distal from the joint itself, if you encounter strong resistance to disarticulation in the following steps you may need to make additional cuts more proximally on the capsule.

17. Extend these cuts posteriorly on both the lateral and medial sides leaving only the capsule and ligaments posterior to the joint intact.

18. Flex (elevate) the thigh to approximately 45 degrees and flex the knee to approximately 45 degrees.

If the knee cannot be flexed due to tension in the quadriceps muscle group, you can transect the patellar ligament near the attachment to the tibia (we will be performing that transection below so this early transection will not disrupt examination of the knee).

19. Rotate the limb such that the foot moves medially (i.e. external rotation at the hip) which should dislocate the hip joint and open the space between the femur and the acetabulum on the pelvis.

The joint is internally reinforced by a central ligament (ligamentum teres femoris) that needs to rupture in order for the joint to open.

This can require considerable force. Have one member of your team lean on the contralateral anterior superior iliac spine to hold the pelvis stable while twisting the hip joint.

If there is excessive resistance to the rotation, you likely need to extend the capsule/ligament incision more laterally/medially around the joint and/or transect capsule tissue closer to the pelvis. There is a natural tendency to make the capsular transection too distal resulting in residual ligaments preventing disarticulation.

20. As you push the joint open, observe a fibrocartilaginous labrum that deepens the rim of the acetabulum improving stability of the joint.
    (Figure545) (Netter477)

21. Holding the hip joint open, examine inside at the head of the femur and observe the smooth articular cartilage and the centrally located ligamentum teres femoris (also known as the ligament of the head of the femur).
    (Netter477)

The ligamentum teres femoris spans inside the joint itself from a central depression on the head of the femur across to the acetabular fossa of the pelvis.

The ligamentum teres femoris is ruptured during disarticulation of the hip and you will observe the broken ends attached to each bone.

This ligament appears to have little impact on strengthening or stabilizing the hip joint past childhood.

22. Reverse the rotation motions above to restore the dislocated femur into the acetabulum of the pelvis.

Restoring bones to their correct positions following a dislocation injury is called reduction of the joint.

It is somewhat uncommon for the hip to dislocate without fracture or an underlying musculoskeletal disorder. When occurring, hip dislocation is usually the result of high energy impact (e.g. motor vehicle accident or fall from significant height).

PROCEDURE - THE KNEE

23. The knee joint consists of articulating surfaces between the tibia and the femur, with the patella articulating to the femur anteriorly.
    (NetterBP112)
    (iPhoto5003)

The knee joint is a modified hinge joint. It combines the actions of hinge (primary function), pivot, and gliding joints.

The knee joint bony arrangement is inherently unstable, but the surrounding muscle tendons, the stout capsule, the intrinsic and extrinsic ligaments, and cartilage menisci impart stability.

A number of synovial bursae surround the knee joint, some of which have fluid communication with the fluid of the knee joint. These bursae are rarely identifiable in donors. They act as cushions and lubrication sacs preventing tissue abrasion when tendons move.

24. Remove any remaining skin over the anterior, lateral, and medial sides of the joint.

25. Identify the patella and the enveloping quadriceps tendon.
    (Figure538) (Netter498) (Photo5041)
    (iPhoto5003)

The quadriceps tendon is a shared tendon for the four quadriceps muscles; vastus lateralis, rectus femoris, vastus medialis, and vastus intermedius.

The tendon envelops all but the articular surface of the patella then continues downward to attach to the tibial tuberosity inferiorly.

Superior to the patella the tendon is referred to as the quadriceps tendon. Inferiorly to the patella the structure is called the patellar ligament or patellar tendon.

26. Transect the patellar tendon just superior to its tibial tuberosity attachment.
    (Figure538) (Netter498) (Photo5042)

27. Reflect the tendon and patella superiorly and examine the deep surface.
    (Netter498) (Photo5051)

The deep surface of the patella is covered by smooth articular cartilage. This surface articulates with the intercondylar fossa of the femur. This allows the patella to slide relative to the femur as the knee flexes or extends.

In most individuals there will be a prominent adipose deposit deep to the patellar tendon, referred to as the patellar fat pad.

28. Return to the gracilis, semitendinosus and sartorius muscles and follow them distally to where their tendons merge at the medial side of the knee before inserting into the tibia.
    (Netter497) (Photo5043)

The tendons of gracilis, semitendinosus and sartorius at this point are collectively called the pes anserinus (from the Latin, “goose’s foot”).

The pes anserinus is unusual in that it is a shared attachment for one muscle of each of the three thigh compartments (gracilis medial, semitendinosus posterior, and sartorius anterior).

29. Retract the pes anserinus and examine the medial collateral ligament of the knee partially obscured by the pes anserinus.
    (Figure538) (Netter497) (Photo5052)

The medial collateral ligament is a broad, flat, and membranous ligament attached to the medial femur and tibia. The ligament is tightly integrated with the capsule and the edge of the medial meniscus.

Thus, the ligament is not a separate structure. Any/all of the tissue against the medial side of the knee joint is part of the medial collateral ligament.

The medial collateral ligament (MCL) is often called the tibial collateral ligament, due to its tibial attachments.

30. Move to the lateral side of the knee and dissect into the space between the iliotibial tract and the tendon of the biceps femoris muscle to expose part of the lateral collateral ligament.
    (Figure538) (Netter497) (Photo5044)

The lateral collateral ligament is narrower and more cord-like than the medial collateral ligament. The ligament extends inferiorly and posteriorly from the lateral epicondyle of the femur to attach to the head of the fibula.

Unlike the medial collateral ligament, the lateral collateral ligament is distinctly separate from the joint capsule and lateral meniscus.

The lateral collateral ligament (LCL) is often called the fibular collateral ligament, due to its fibular attachments.

31. Make an incision through the anterior knee joint capsule and flex the knee to partly open the capsule.

32. Observe the articular surfaces of the femur and tibia visible with this partial opening of the joint.
    (Figure539) (Netter498) (Netter500) (Photo5045) 

Each femoral condyle articulates with its corresponding tibial condyle. The medial condyle is slightly larger than the lateral condyle.

Situated on top of each tibial condyle are the menisci, C-shaped cartilages, that help stabilize the joint. These cartilages will be seen more clearly in steps later in the dissection. 

33. Use a blunt probe to clean synovial membrane away from the intracapsular cruciate ligaments at the midline inside the joint.
    (Figure539) (Netter500) (Photo5053)

These ligaments receive their names based on the relative positions of their tibial attachments to the bone between the condyles, the intercondylar crest. The ligaments cross each other to form a X-like shape (thus, the name 'cruciate' meaning cross-shaped).

The anterior cruciate ligament (ACL) runs from the anterior side of the tibia intercondylar crest to the medial side of the lateral femoral condyle.

The posterior cruciate ligament (PCL) runs from the posterior side of the intercondylar crest to lateral side of the medial femoral condyle. This ligament is often difficult to see due to the posterior position 'behind' the ACL.

The most stable position for the knee is at full extension (straight), which is the typical standing posture.

CLINICAL EXERCISE - Lachman Test

34. Injury to the ligaments of the knee is one of the most common sports related injuries. In particular, due to the nature of sports engaging in rapid changes in direction, injury to the anterior cruciate ligament is common.

In this clinical exercise, you have the chance to perform the Lachman Test on the knee with the anterior cruciate ligament intact, and then again with the anterior cruciate ligament transected to demonstrate function of that ligament. For the steps to take:
                                  ----- click here ------

35. On the knee with the transected ACL, flex the knee sufficiently to expose the deeper surface of each tibial condyle to examine the cartilage menisci.
    (Figure540) (Netter499) (Photo5045) (Photo5053)

You may need to extend the capsule incision partway through the medial and lateral sides to open the joint sufficiently to see the menisci clearly.

The menisci are C-shaped articular cartilage structures located laterally and medially within the knee joint. The medial meniscus forms a slightly larger/wider C-shape than the lateral meniscus. These act to deepen the socket and help stabilize the joint. 

The menisci connect into the capsule structure at the periphery, but are not directly attached to the bone of the tibia. This allows the cartilage to move slightly as the knee goes through the full range of motion.

PROCEDURE - THE ANKLE

36. The ankle joint (talocrural joint) consists of several articulating surfaces between the fibula and talus and the tibia and talus.
    (Netter515) (Netter516) (Netter517) 

The ankle joint is a hinge joint with movements of dorsiflexion and plantar flexion.

The talus is wider anteriorly than posteriorly, and as a result, the joint is most stable in dorsiflexion. As a consequence, most ankle sprains occur when the foot is in plantar flexion and is most unstable (e.g. stepping off a curb, landing from a jump, etc.)

The talocrural joint is stabilized by a strong fibrous capsule and extracapsular ligaments on the lateral and medial sides of the ankle joint (connecting the calcaneus, talus, navicular bones).

The medial ligament complex is collectively called the deltoid ligament. This ligament is constructed from subdivisions based on the bones they connect, but we will not examine those.
    (Figure537) (Netter518)

The lateral ligament complex is also constructed by subdivisions based on the bones they connect, but we will not examine all of those specifically. However, the anterior talofibular ligament (part of the lateral ligament complex) is the most commonly sprained ligament of the ankle.
    (Figure537) (Netter518)

The other ankle stabilizing joint is the distal tibiofibular joint between the tibia and fibula. This is a syndesmosis type of joint, which is a slightly moveable articulation between bones that is united by ligaments, in this case the tibiofibular ligaments and the interosseous membrane spanning between the tibia and fibula.
    (Figure537) (Netter517) (Netter505)

Sprains of the tibiofibular ligaments are commonly called high ankle sprains. Bony instability of this region can occur with fractures or separation of the joint and require stabilizing hardware (which you performed in a mock procedure in a previous lab).

PROCEDURE - FOOT JOINTS

37. We will not dissect all the joints of the foot, but take some time after lab to review their organization from lecture and your atlas.
    (Netter515) (Netter516) 

The joints are named based on the bones located to each side of the individual joints. The main joints are:

Subtalar joint - The articular surfaces between the talus and the calcaneus form the subtalar joint. This joint allows for inversion and eversion of the foot (playing no role in plantar flexion or dorsiflexion).

Talonavicular joint - The surfaces between the talus and the navicular form the talonavicular joints.

Calcaneocuboid joint - The joint surfaces between the calcaneus and the cuboid bone form the calcaneocuboid joint.

Transverse tarsal joint - Collectively, the talonavicular and calcaneocuboid joints form the transverse tarsal joint.

The subtalar, talonavicular, and calcaneocuboid joints form a complicated triple articulation allowing inversion and eversion. Such movements are essential to normal locomotion, especially on rough or uneven surfaces.

Tarsometatarsal joints - The bony skeleton of the foot includes several articulation points between the metatarsal bones and the cuneiform/cuboid bones. 

Metatarsophalangeal joints - These joints allow movements occur in several planes to effect flexion, extension, abduction, adduction, and circumduction of the toes.

Interphalangeal joints - These joints are articulations between each of the phalanges. Interphalangeal joints are hinge joints with movements of flexion and extension of the toes.

CHECKLIST

Structures

Dorsum of the foot
    Tibialis anterior tendon
    Extensor digitorum longus tendon
    Fibularis tertius tendon
    Extensor hallucis longus tendon
    Dorsalis pedis artery
    Extensor digitorum brevis muscle and tendon
    Extensor hallucis brevis muscle and tendon

Hip joint
    Labrum
    Ligamentum teres femoris

Knee joint
    Patella
    Patella ligament
    Lateral collateral ligament (LCL)
    Medial collateral ligament (MCL)
    Lateral meniscus
    Medial meniscus
    Anterior cruciate ligament (ACL)