When discussing lower body mobility, reference is made to the hip joint and pelvic girdle, the knee joint, and finally the ankle joint. Our previous section covered the movement of the pelvis and the trunk muscles that controlled it. Therefore, this next section briefly covers mobility and stability of the hip, knee, and ankle joints.
Basics of Hip Joint
The hip joint, or acetabular femoral joint, is a sphenoid or ball and socket joint formed by the articulation of the acetabulum of the pelvis with the head of the femur. It is a relatively stable joint due to its bony architecture (deep socket) along with its strong ligaments and strong supportive muscles
Mobility/ROM and Movements
There is much variance in hip ROM due to individual differences; therefore, there is some disagreement about the exact possible ROM of each movement associated with the hip joint. The ranges are:
- Flexion: 0 to 130 degrees
- Extension: 0 to 30 degrees
- Abduction: 0 to 35 degrees
- Adduction: 0 to 45 degrees
Basics of the Pelvis
The pelvic girdle consists of a right and left pelvic bone joined together posteriorly by the sacrum. The sacrum can be considered an extension of the spinal column with five fused vertebrae. Extending inferior to the sacrum is the coccyx. The pelvic bone consists of three bones: the ilium, the ischium, and the pubis.
Movements of the Pelvic Girdle
The pelvic girdle moves back and forth within three planes of motion for a total of six different movements:
- Sagittal plane: anterior and posterior tilt
- Frontal plane: lateral rotation (left and right)
- Transverse: left and right rotation
Quads, Hip Flexors, Hamstrings (passive and dynamic)
Hip Flexor Test
This first test is commonly called the Thomas Test and used for testing hip flexor length. The muscles associated with hip flexion are:
- Iliopsoas
- Action: hip flexion
- Length test: hip extension, with the knee in extension
- Rectus Femoris
- Action: hip flexion and knee extension
- Length test: hip extension and knee flexion
- Tensor Fascia Latae (not specifically tested here – Ober Test used to test this and not included in Wexford’s overall assessments)
- Action: hip abduction, flexion, and internal rotation as well as knee extension
- Length test: N/A
- Sartorius
- Action: hip flexion, abduction, and external rotation as well as knee flexion
- Length test: hip extension, adduction, and internal rotation as well as knee extension.
As noted many of these muscles perform hip flexion and knee extension along with their specific actions. The purpose here is to perform the basic tests for hip flexion and knee extension to identify any straightforward deficit.
Starting position
Subject/trainee sits at the end of the testing table, with the thigh almost completely on the table surface. The subject being testing lies down (supine position) on the testing table with the lower leg hanging off the end of the table. The subject then holds the thigh, pulling the knee toward the chest only enough to flatten the low back and sacrum on the testing surface.
Test Movement
If the right knee is flexed toward the chest, the left thigh is allowed to drop toward, with the left knee flexed over the end of the table. With four muscles involved in this length test, variations will likely ensue requiring numerous interpretations based on what is normal, slight, moderate, or marked. The tester is to view if the posterior thigh stays flat on the testing surface, low back flat, and if the lower leg hangs straight down or to a minimum of 80 degrees flexion. This measures the two joint hip flexors (cross hip and knee) specifically the rectus femoris. If thigh rises, it is an indication of both one and two joint hip flexor muscles have issues (shortness).
Passive Straight-Leg Raise
Starting Position
Supine with legs extended and the low back and sacrum flat on the testing surface. With the low back and sacrum fixed, the tester will instruct the subject to fully relax the leg then lift the leg upward. The tester will continue to lift leg until tester feels a pulling or tightness in the hamstrings. Note the angle of both legs (use goniometer if available or a movement analysis system used in the demonstration picture)
One the passive leg raise is complete, from the end passive position, have subject flex quadriceps (thigh) muscles and dynamically pull the leg back further under their own power until the pelvis begins to posteriorly tilt. This is the end position of the dynamic portion of the hamstring length test to test the hamstring length in a dynamic condition. An angle greater than 80 degrees is considered a good test.
Back Flexibility and Hamstring Length (Sit and Reach Test)
Starting Position: Sitting with legs extended (long-sitting) and feet, at, or slightly below right angles
Test Movement: Reach forward, with knees straight, and attempt to touch the toes with the fingertips (base of big toe) or beyond this point, reaching as far as the ROM of the muscle length permits.
Normal Range of Motion in Forward Bending: Normal hamstring length permits the pelvis to flex forward toward the thigh permitting the angle between the sacrum and the testing surface to be approximately 80 degrees. Normal flexion of the lumbar spine allows the spine to flatten. Normal flexion of the thoracic spine allows an increase in the posterior convex shape which is seen as a smooth, continuous curve in this area. The average adult should be able to touch their toes in forward bending with the knees straight depending on the flexibility of the back and length of the hamstrings.
The Knee Joint
The knee joint is the largest diarthrodial (synovial) joint in the body. It is primarily a hinge joint *
(modified Ginglymus), however, this joint also performs slight flexion (lateral and medial) as well as slight rotation. The combined functions of weight-bearing and locomotion induce (place or produce) considerable stress, strain, compression, and torsion on this joint. Powerful knee joint extensors and flexor muscles, combined with a strong ligamentous structure, provide a strong functioning joint in most instances.
Knee ROM
Basic knee ROM varies (based on the reporting textbook/manual, etc.; however the standard range of motion is:
- Extension – 0 degrees (do not want hyperextension)
- Flexion – up to 140 degrees
- Range – 0 to 140 degrees
Ankle Joint
The ankle joint is commonly referred to as the talocrural joint and is considered a hinge or ginglymus-type joint. Specifically, it is comprised of the talus, the distal tibia, and the distal fibula. The typical range of motion is:
- Plantar flexion (pointing the toes) – 45 -50 degrees
- Dorsi-flexion (pulling the toes toward the lower leg or dorsum) – 15 to 20 degrees
- Range – 65 degrees total for both combined
Dorsi/Plantar Flexion ROM
Testing for Ankle Movements
One-joint Plantar Flexors (Soleus and Popliteus)
Starting position: sitting, with hip and knee flexed
Test Movement: with the knee flexed 90 degrees or more to make the two-joint gastrocnemius and plantaris slack over the knee joint, dorsiflex the foot. Sit forward in a chair with knees bent and feet pulled back toward the chair enough to raise heels from the floor. Press down on the thigh to help force heel to the ground.
Two-joint Plantar Flexors (Gastrocnemius and Plantaris)
Starting Position: standing position with knees extended (unless hamstring tightness cause the knee to flex)
Test Movement: Stand erect on a board inclined approximately 10 degrees, with feel approximately 8 t0 10 degrees of out-toeing, with the knee in extension to elongate the gastrocnemius and plantaris over the knee joint, dorsiflex the foot.
You can learn more about mobility, biomechanics, and training in our online Biomechanics Specialist course.
