The cause of in-toeing can be differentiated based on the location of the disalignment. The variants are:

- Curved foot (metatarsus adductus)

- Twisted shin (tibial torsion)

- Twisted thighbone (femoral anteversion)

The tibia or lower leg slightly or severely twists inward when walking or standing.

Cubitus varus (varus means a deformity of a limb in which part of it is deviated towards the midline of the body) is a common deformity in which the extended forearm is deviated towards midline of the body.

Cubitus varus is often referred to as "Gunstock deformity", due to the crooked nature of the healing.

The "opposite" condition is cubitus valgus.

As with certain cases of flat feet, high arches may be painful due to metatarsal compression; however, high arches— particularly if they are flexible or properly cared-for—may be an asymptomatic condition.

People with pes cavus sometimes—though not always—have difficulty finding shoes that fit and may require support in their shoes. Children with high arches who have difficulty walking may wear specially-designed insoles, which are available in various sizes and can be made to order.

Individuals with pes cavus frequently report foot pain, which can lead to a significant limitation in function. The range of complaints reported in the literature include metatarsalgia, pain under the first metatarsal, plantar fasciitis, painful callosities, ankle arthritis, and Achilles tendonitis.

There are many other symptoms believed to be related to the cavus foot. These include shoe-fitting problems, lateral ankle instability, lower limb stress fractures, knee pain, iliotibial band friction syndrome, back pain and tripping.

Foot pain in people with pes cavus may result from abnormal plantar pressure loading because, structurally, the cavoid foot is regarded as being rigid and non-shock absorbent and having reduced ground contact area. There have previously been reports of an association between excessive plantar pressure and foot pathology in people with pes cavus.

Instances in which the medial epicondyle of the distal humerus is malformed due to the initial fracture at the humeral endplate may result in subluxation (snapping) of the ulnar nerve over the medial epicondyle with active flexion and extension of the elbow. In such instances, conductance of the ulnar nerve may be compromised due to chronic irritation, potentially resulting in irreversible ulnar neuropathy.

On weightbearing projectional radiography, pes cavus can be diagnosed and graded by several features, the most important being medial peritalar subluxation, increased calcaneal pitch (variable) and abnormal "talar-1st metatarsal angle" (Meary's angle). Medial peritalar subluxation can be demonstrated by a medially rotated talonavicular coverage angle.

Children until the age of 3 to 4 have a degree of Genu Varum. The child sits with the soles of the feet facing one another; the tibia and femur are curved outwards; and, if the limbs are extended, although the ankles are in contact, there is a distinct space between the knee-joints. During the first year of life, a gradual change takes place. The knee-joints approach one another; the femur slopes downward and inward towards the knee joints; the tibia become straight; and the sole of the foot faces almost directly downwards.

While these changes are occurring, the bones, which at first consist principally of cartilage, are gradually becoming ossified. By the time a normal child begins to walk, the lower limbs are prepared, both by their general direction and by the rigidity of the bones which form them, to support the weight of the body.

In clubfoot one or both feet are rotated inwards and downwards. The affected foot, calf, and leg may be smaller than the other. In about half of those affected, both feet are involved. Most cases are not associated with other problems. Without treatment, people walk on the sides of their feet which causes issues with walking.

If a child is sickly, either with rickets or any other ailment that prevents ossification of the bones, or is improperly fed, the bowed condition may persist. Thus the chief cause of this deformity is rickets. Skeletal problems, infection, and tumors can also affect the growth of the leg, sometimes giving rise to a one-sided bow-leggedness. The remaining causes are occupational, especially among jockeys, and from physical trauma, the condition being very likely to supervene after accidents involving the condyles of the femur.

The degree of genu valgum can be estimated by the , which is the angle formed by a line drawn from the anterior superior iliac spine through the center of the patella and a line drawn from the center of the patella to the center of the tibial tubercle. In women, the Q angle should be less than 22 degrees with the knee in extension and less than 9 degrees with the knee in 90 degrees of flexion. In men, the Q angle should be less than 18 degrees with the knee in extension and less than 8 degrees with the knee in 90 degrees of flexion. A typical Q angle is 12 degrees for men and 17 degrees for women.

Genu valgum, commonly called "knock-knee", is a condition in which the knees angle in and touch each other when the legs are straightened. Individuals with severe valgus deformities are typically unable to touch their feet together while simultaneously straightening the legs. The term originates from the Latin "genu", "knee", and "valgus" which actually means bent outwards, but in this case, it is used to describe the distal portion of the knee joint which bends outwards and thus the proximal portion seems to be bent inwards. For citation and more information on uses of the words Valgus and Varus, please visit the internal link to -varus.

Mild genu valgum is diagnosed when a person standing upright with the feet touching also shows the knees touching. It can be seen in children from ages 2 to 5, and is often corrected naturally as children grow. However, the condition may continue or worsen with age, particularly when it is the result of a disease, such as rickets or obesity. Idiopathic genu valgum is a form that is either congenital or has no known cause.

Other systemic conditions may be associated, such as Schnyder crystalline corneal dystrophy, an autosomal dominant condition frequently reported with hyperlipidemia.

Hallux varus, or sandal gap, is a deformity of the great toe joint where the hallux is deviated medially (towards the midline of the body) away from the first metatarsal bone. The hallux usually moves in the transverse plane. Unlike hallux valgus, also known as hallux abducto valgus or bunion, hallux varus is uncommon in the West but it is common in cultures where the population remains unshod.

Cubitus valgus is a medical deformity in which the forearm is angled away from the body to a greater degree than normal when fully extended. A small degree of cubitus valgus (known as the carrying angle) is acceptable and occurs in the general population.

When present at birth, it can be an indication of Turner syndrome or Noonan syndrome. It can also be acquired through fracture or other trauma. The physiological cubitus valgus varies from 3° to 29°. Women usually have a more pronounced Cubitus valgus than men. The deformity can also occur as a complication of fracture of the lateral condyle of the humerus, which may lead to tardy/delayed ulnar nerve palsy.

The opposite condition is cubitus varus ().

Clubfoot is a birth defect where one or both feet are rotated inwards and downwards. The affected foot, calf, and leg may be smaller than the other. In about half of those affected, both feet are involved. Most cases are not associated with other problems. Without treatment, people walk on the sides of their feet which causes issues with walking.

The exact cause is usually unclear. A few cases are associated with distal arthrogryposis or myelomeningocele. If one identical twin is affected there is a 33% chance the other one will be as well. Diagnosis may occur at birth or before birth during an ultrasound exam.

Initial treatment is most often with the Ponseti method. This involves moving the foot into an improved position followed by casting, which is repeated at weekly intervals. Once the inward bending is improved, the Achilles tendon is often cut and braces are worn until the age of four. Initially the brace is worn nearly continuously and then just at night. In about 20% of cases further surgery is required.

Clubfoot occurs in about one in 1,000 newborns. The condition is less common among the Chinese and more common among Maori. Males are affected about twice as often as females. Treatment can be carried out by a range of healthcare providers and can generally be achieved in the developing world with few resources.

Diagnosing the congenital clasped thumb is difficult in the first three to four months of life, as it is normal when the thumb is clutched into the palm in these first months.

Diagnoses that cause the same flexion or adduction abnormalities of the thumb are:

- Congenital clasped thumb

- Congenital Trigger thumb (flexion of the interphalangeal joint) - Trigger finger

- Spasticity: overstimulation of muscles

Syndrome associated flexion-adduction of the thumb:

- Freeman-Sheldon syndrome (a congenital, heritable affection of the face, the hands, the feet and some joints)

- Distal arthrogryposis

- MASA syndrome

- X-linked hydrocephalus

- Adducted thumb syndrome

- Waardenburg syndrome

- Whistling face syndrome (Freeman-Sheldon syndrome)

- Digitotalar dysmorphism

- Multiple pterygium syndrome

The thumb contains five groups of muscle and/or tendons:

1. Extensor tendons (to stretch the thumb)

2. Flexor muscles/tendons (to bend the thumb)

3. Abductor muscles/tendons (to move the thumb outwards)

4. Adductor muscle (to move the thumb inwards)

5. Opposing muscles (to move the thumb opposite the small finger)

In order for the thumb to maintain a normal position, a strict balance between these groups is required. Weak or absent extensors and/or abductors (the extensor pollicis brevis tendon, the extensor pollicis longus tendon or, rarely, the abductor pollicis longus tendon), can cause a disbalance, leading to an abnormal position of the thumb: congenital clasped thumb. There is also the possibility that two tendons are affected simultaneously.

The following tendon deviations can induce congenital clasped thumb:

- The flexor tendons are too short (the thumb is drawn into the palm)

- The abductor tendons are hypoplastic or absent

- The extensor tendons are hypoplastic or absent

Furthermore, a tight thumb web space (the area between thumb and index finger) can contribute to congenital clasped thumb. The thumb cannot be properly abducted (moved outwards), if the web space is too tight.

To summarize, the causes of congenital clasped thumbs may vary between patients and can sometimes be a combination of the preceding components. Treatment should be tailored to all occurring components in order to achieve good results.

Patients often complain of pain and swelling over the medial aspect of the knee joint. They may also report instability with side-to-side movement and during athletic performance that involves cutting or pivoting.

Tibial plateau fractures typically presents with knee effusion, swelling of the knee soft tissues and inability to bear weight. The knee may be deformed due to displacement and/or fragmentation of the tibia which leads to loss of its normal structural appearance. Blood in the soft tissues and knee joint (hemarthrosis) may lead to bruising and a doughy feel of the knee joint. Due to the tibial plateau's proximity to important vascular (i.e. arteries, veins) and neurological (i.e. nerves such as peroneal and tibial) structures, injuries to these may occur upon fracture. A careful examination of the neurovascular systems is imperative. A serious complication of tibial plateau fractures is compartment syndrome in which swelling causes compression of the nerves and blood vessels inside the leg and may ultimately lead to necrosis or cell death of the leg tissues.

The Segond fracture is a type of avulsion fracture (soft tissue structures tearing off bits of their bony attachment) of the lateral tibial condyle of the knee, immediately beyond the surface which articulates with the femur.

The classic clinical presentation of a hip fracture is an elderly patient who sustained a low-energy fall and now has groin pain and is unable to bear weight. Pain may be referred to the supracondylar knee. On examination, the affected extremity is often shortened and unnaturally, externally rotated compared to the unaffected leg.

Jacobson previously described the common problems to medial knee surgery. It was stressed that adequate diagnosis is imperative and all possible injuries should be evaluated and addressed intraoperatively. Damage to the saphenous nerve and its infrapatellar branch is possible during medial knee surgery, potentially causing numbness or pain over the medial knee and leg. As with all surgeries, there is a risk of bleeding, wound problems, deep vein thrombosis, and infection that can complicate the outcome and rehabilitation process. The long term complication of arthrofibrosis and heterotopic ossification (Pellegrini-Stieda syndrome) are problems that are best addressed with early range of motion and following defined rehabilitation protocols. Failure of graft due to intrinsic mechanical forces should be prevented with preoperative alignment assessment (osteotomy treatment) and proper rehabilitation.

Patients often complain of pain and instability at the joint. With concurrent nerve injuries, patients may experience numbness, tingling and weakness of the ankle dorsiflexors and great toe extensors, or a footdrop.

A tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci can be torn during innocuous activities such as walking or squatting. They can also be torn by traumatic force encountered in sports or other forms of physical exertion. The traumatic action is most often a twisting movement at the knee while the leg is bent. In older adults, the meniscus can be damaged following prolonged 'wear and tear' called a degenerative tear.

Tears can lead to pain and/or swelling of the knee joint. Especially acute injuries (typically in younger, more active patients) can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the knee joint. The joint will be in pain when in use, but when there is no load, the pain goes away.

A tear of the medial meniscus can occur as part of the unhappy triad, together with a tear of the anterior cruciate ligament and medial collateral ligament.

A tibial plateau fracture is a break of the upper part of the tibia (shinbone) that involves the knee joint. Symptoms include pain, swelling, and a decreased ability to move the knee. People are generally unable to walk. Complication may include injury to the artery or nerve, arthritis, and compartment syndrome.

The cause is typically trauma such as a fall or motor vehicle collision. Risk factors include osteoporosis and certain sports such as skiing. Diagnosis is typically suspected based on symptoms and confirmed with X-rays and a CT scan. Some fractures may not be seen on plain X-rays.

Pain may be managed with NSAIDs, opioids, and splinting. In those who are otherwise healthy, treatment is generally by surgery. Occasionally, if the bones are well aligned and the ligaments of the knee are intact, people may be treated without surgery.

They represent about 1% of broken bones. They occur most commonly in middle aged males and older females. In the 1920s they were called a "fender fracture" due to their association with people being hit by a motor vehicle while walking.

Because of the high rate of associated ligamentous and meniscal injury, the presence of a Segond or reverse Segond fracture requires that these other pathologies must be specifically ruled out. Increasingly, reconstruction of the ACL is combined with reconstruction of the ALL when this associated pathology is present. It is often associated with an increased 'pivot shift' on physical exam.