The Ilizarov external fixator is an external skeletal fixator that is used to stabilize or lengthen the limb bones. Bone lengthen bone occurs through mechanical distraction on the long axis of the bone, thus the method of lengthening is called distraction osteogenesis. This method has been shown successful. Unfortunately, it has also been associated with a substantial number of complications.

Muscle shortening and persistent weakness are among the most common complications seen in this procedure. Muscle shortening usually occurs in strong muscle groups such as the planter flexor muscles, as a result of strength imbalance between the opposing muscle groups. Shortening may persist for more than a year after the removal of the fixator and may require surgical intervention. Fortunately, muscular shortening can be prevented by splinting and physiotherapy in the form of stretching and strengthening exercise and functional training.

The use of different exercises in rehabilitation can help accomplishing different therapeutic goals. Thus, the choice to use one or the other should depend on the desired treatment goals. Weight bearing (CKC) and non weight bearing (OKC) exercise has been incorporated into rehabilitation; however, the effects of these two types of exercises particularly on muscle flexibility and mechanics have never been studied systematically.

Therefore, the purpose of this is to compare the effects of OKC and the CKC exercise on muscle strength, architecture and flexibility.

General Hypothesis:

The use of open kinetic or closed kinetic chain exercises will have no different effects on muscle function or internal organization during tibial distraction osteogenesis by Ilizarov's method Specific hypotheses

1. There will be no difference between the effects of OKC and CKC on muscle flexibility.
2. There will be no difference between the effect of OKC and CKC exercises on muscle strength.
3. There will be no difference between the effect of OKC and CKC on the internal organization of muscle specifically the pennation angle, muscle thickness and fiber length.
4. There will be no difference between the overall of OKC and CKC exercise on the functional performance of patients.

First, personal information and history of each subject will be collected. Then, patients will be informed and receive a full oral explanation of the purpose and procedures of the study before they will be asked to sign an informed consent form.

An initial assessment will be done at the end of latent period (5-7 days) and then every 2 weeks thereafter for a period of 3-5cm distraction or the end of distraction period whatever is earlier.

Patients enrolled in this study will be divided randomly into two groups (A & B). Group A (OKC): will consist of 10 patients receiving open-kinetic- chain exercise program. Group B (CKC) will consist of 10 patients receiving closed-kinetic- chain exercise program.

Initially, each patient will be assessed using the Borg scale to determine the number of strengthening exercise repetitions that patient can carry out. Assessment will be repeated weekly, before the number of repetition is progressed. For stretching exercise, 5 repeat ions will be done each session, in addition patients will be asked to repeat the exercise as a home program exercise. Exercise will be given 3 times weekly, at the University of Benha outpatient clinic, for a period of 3-5 cm of distraction (approximately 8 weeks) or the end of distraction whatever is earlier Exercise for group (A) Knee flexion exercise Patient in supine and gently bend his knee, with keeping the heel in contact with the bed. Bring the heel towards bottom as far as is comfortable .Exercise will be repeated as determined by patient's ability.

Strength the hamstring muscle Patient will be in prone lying position with the knee free out of the bed. Patient will then be asked to bend his knee by making the heel touches his bottom.

Strength quadriceps muscle Patient will sit on the edge of bed or on chair with the thigh supported. Patient will be asked to keep his trunk upright. Then, the knee will be straightened and will be held with the toes pointing to the ceiling for 6 seconds.

Stretch hamstring from sitting:

Patients will assume the long sitting position with their non-operated extremity hanging over the edge of the bed. Patients will then lean forward, grasp his/her forefoot and dorsiflex the ankle while maintaining the knee extended. This position will be maintained for 20-60 seconds before returning to the starting position. The whole exercise will be repeated for 5 times.

Stretch hamstring from prone:

Patients will assume a prone lying position. The legs of the operated limb will be positioned in a neutral rotation and will be allowed to hang freely, over the edge of the bed, by the weight of leg and apparatus as well as by the pulling effect of the gravity. This position will be maintained for duration ranges from 1 minute to as long as tolerated by every individual patient. Patients will also be instructed to assume this position frequently at home during some daily activities e.g. while watching television or reading a book.

Strength hip extensor and abductors:

Patient will be prone with extended knee. Patient will be asked to raise the lower limb upward with the knee extended. For abductor strengthening, the patient will be in a side lying position on the non-operated limb and will be asked to raise the upper limb upwards while the knee is kept straight.

Calf-muscles stretch:

To stretch the gastrocnemius, the patient's heel will be grasped while the knee is extended. Then, the calcaneus will be pulled caudally, with the thumb and fingers of the therapist, before the heads of the metatarsals are gently pushed upwards. The end position will be held for 20-60 seconds before rest is allowed.

Strength exercise for dorsiflexors plantar flexors Patient in long sitting using Theraband one end by his hands and the other end secure around metatarsal bone then the patient will perform plantar flexion against resistance of surgical tubing repeat 10 times.

Exercise for group (B) Wall slides Patient will stand with back against a wall, and feet straight in front of him. Patient then slide down keeping back against the wall, until becoming in a slight sitting position. Slide down only as far as patient feel comfortable. For the first few times patient do this knee exercise, hold the sitting position for a few seconds, then slide back up repeat 10 times.

Foot sliding from sitting While patient is sitting on a smooth surface, the patient pulls the heel of involved leg toward buttocks, flexing the knee as much as tolerable. Hold and straighten leg by sliding heel downward.

Hamstring and quadriceps co-contraction from sitting From a relaxed sitting position with both knees bent to 90 degrees, the patients will be instructed to press firmly on the ground. This exercise will also be done using a stepper machine. Patient was instructed to press rhythmically on the feet plate of a stepper machine, while maintaining the feet in complete contact with the plate, so that heels were vertical.

Bridging exercise:

Patient will assume the crock lying position. In this position, the knees were bent to 30-45 degrees while the feet are completely resting on the supporting surface by placing a firm wedge underneath the feet to accommodate them to the supporting surface. Then, patients will be instructed to raise their lower back and pelvis, while bearing weight on both lower limbs, until the thighs lies in line with pelvis and trunk.

Side-to side, forward and backward weight shifting:

Patient will assume an erect standing position. Both feet will be placed slightly apart with the operated limb placed parallel to, in front of and behind the sound side during side-to-side, forward and backward weight shifting exercise, respectively.

Sitting-to-standing:

Patient will assume a relaxed sitting position. The foot of the affected extremity will be placed initially in front, later, behind the other side. Patient will be instructed to assume the standing positing, while bearing as much weight as they can on their affected extremities.

Lunge exercise:

Patient will assume the forward lunge position. In this position, the affected limb will be placed in front of the other. The distance through which each subject lunged forward will be determined by each individual's leg length as the feet should be about 2 to 3 feet apart, depending on patient's leg length. Then, each subject will move from an upright standing position to the forward lunge position, and back to the starting position.

Squatting exercise:

Patient will be instructed to stand erect, between the parallel bars, with their feet parallel and slightly apart. While maintaining the back erect, they will be instructed to bend both knees slightly then to return back to the erect standing position by pushing against the feet.

Standing Toe Raises:

This exercise is more advanced than the seated toe raise, as it places the entire weight of the body on the exercised leg. Stand upright on both feet Push down through the toes lifting both heels off the ground

Standing Hamstring Stretch:

Patient will stand in front of an elevated surface. Place the operated leg on the surface, Lean forward from the hips until a gentle hamstring stretch is felt on the underside of the thigh. Once a gentle hamstring stretch is felt on the underside of the thigh, hold this position for 30 seconds

Inclusion Criteria:

• Referred from an orthopedic surgeon with diagnosis of tibial lengthening or deformity correction by Ilizarov's external fixator.
• unilateral or bilateral tibial distraction osteogenesis.

Exclusion Criteria:

• Patients with Ilizarov due to neurological causes (e.g. poliomyelitis) or other neuromusculoskeletal disease that could affect muscle function and innervations.
• Ankle or knee joints are included in the Ilizarov frame.
• Patients developed neurological complications that interfere with rehabilitation after the application of the Ilizarov apparatus.